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Abbreviation (ISO4): Prog Chem      Editor in chief: Jincai ZHAO

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Progress in Chemistry >

2024 , Vol. 36 >Issue 6: 867 - 877

DOI: https://doi.org/10.7536/PC231020

Review

Photocatalytic Methane Oxidation to Methanol in Promoting Methane Conversion Rate and Methanol Selectivity

  • Chunqiu Han 1, 2 ,
  • Yuehan Cao , 1, 2, * ,
  • Chuan Huang 2 ,
  • Weifeng Lv 2 ,
  • Ying Zhou , 1, 2, *
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  • 1 National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
  • 2 School of New Energy and Materials, Southwest Petroleum University, Chengdu 610500, China
* e-mail: (Yuehan Cao);
(Ying Zhou)

Received date: 2023-10-30

  Revised date: 2024-01-31

  Online published: 2024-03-15

Supported by

National Natural Science Foundation of China(22209135)

National Natural Science Foundation of China(52325401)

National Natural Science Foundation of China(22209136)

China Postdoctoral Science Foundation(2022M722635)

Sichuan Province Innovative Talent Funding Project for Postdoctoral Fellows(BX202220)

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Abstract

Photocatalytic direct conversion of methane(CH4)to methanol(CH3OH)provides an effective way for efficient energy storage and the synthesis of high-value chemicals.However,due to the difficulty in activating CH4molecules and the fact that CH3OH is more reactive than CH4and prone to peroxidation,the conversion rate of CH4is low,and the selectivity of CH3OH is low as well.Therefore,the selective photocatalytic direct conversion of CH4to CH3OH still faces significant challenges.This review focuses on the research ideas on promoting CH4conversion rate and CH3OH selectivity in recent years in the direct conversion of photocatalytic CH4to CH3OH,as well as the corresponding catalyst design strategies.In terms of promoting the CH4conversion rate,the main research idea is to effectively activate CH4by improving reactive oxygen radical activation or catalytic activation pathways.In terms of promoting CH3OH selectivity,the main idea is to inhibit the peroxidation of CH3OH or achieve CH3OH regeneration.In order to improve the conversion rate of CH4and the selectivity of CH3OH,catalytic design strategies mainly include loading cocatalysts,controlling the size of catalytic materials and constructing oxygen vacancies.Finally,this review provides an outlook on the future research direction of photocatalytic direct conversion of CH4to CH3OH .

Contents

1 Introduction

2 Approach of promoting CH4conversion rate

2.1 Reactive oxygen radical activation

2.2 Catalytic activation

3 Strategies for the design of catalysts to enhance the conversion rate of CH4

3.1 Reactive radicals

3.2 Active site of photocatalysts

4 Approach of promoting CH3OH selectivity

4.1 Inhibiting CH3OH peroxidation

4.2 Achieving CH3OH regeneration

5 Conclusion and outlook

Key words： photocatalytic; CH4 conversion; CH3OH; promoting activation of C—H bond; inhibiting CH3OH peroxidation

Cite this article

Chunqiu Han , Yuehan Cao , Chuan Huang , Weifeng Lv , Ying Zhou . Photocatalytic Methane Oxidation to Methanol in Promoting Methane Conversion Rate and Methanol Selectivity[J]. Progress in Chemistry, 2024 , 36(6) : 867 -877 . DOI: 10.7536/PC231020

1 Introduction

Methane(CH4)is the main component of natural gas[1⇓~3]。 the earth is rich in natural gas reserves,and as of 2020,The world's proven natural gas reserves have reached 188.1 trillion cubic meters[4]。 In industry,there are two main uses of CH4:one as a fossil fuel and the other as a feedstock for the production of high-value chemicals[5⇓⇓~8]。 However,the combustion of CH4as a fossil fuel produces large amounts of carbon dioxide(CO2).In the context of the"two-carbon"goal,it is of great significance to convert CH4with abundant hydrocarbon resources into high-value chemicals.Methanol(CH3OH)is liquid at normal temperature and pressure,which makes it easy to store and transport[9,10]。 Its energy density is~17 MJ·I-1,which is about 500 times the energy density of CH4(~36 kJ·I−1 )[11]。 In addition,CH3OH is one of the four basic chemicals,and it is also a raw material for the synthesis of other fine chemicals[12⇓~14]。 In the international market,the demand for CH3OH is huge.According to statistics,in 2020,the demand for CH3OH in the global chemical industry reached 95 million tons,and continued to grow[15]。 Therefore,CH3OH is considered to be one of the ideal products of CH4conversion[16,17]。
However,due to the highly symmetric tetrahedral structure of the CH4molecule,the bond energy of its four equivalent C—H bonds is as high as 434 kJ·mol-1,and its electron affinity(−1.9 eV)and polarizability(2.8×10-40C2·m2·J-1)are low,which causes CH4to show extremely high inertness[18⇓⇓~21]。 Therefore,the C—H bond activation of CH4is very difficult,resulting in low conversion of CH4.In addition,because the activation energy of C—H bond in CH4is much higher than that in CH3OH,and once the first C—H bond of CH4is activated,Continuous dehydrogenation reaction can easily occur,resulting in excessive oxidation of CH3OH to produce CO and CO2,which in turn leads to low selectivity of CH3OH[22⇓~24]。
Industrially,indirect methods are used to convert CH4to CH3OH.Typically,the CH4is first converted to syngas(a mixture of hydrogen and carbon monoxide)at high temperatures(>700°C )[25⇓⇓⇓~29]。 The syngas is then further converted to CH3OH by Fischer-Tropsch synthesis(temperature 150~350℃and pressure Yali 10 bar )[28,30,31]。 This is an energy-intensive process,which also emits a large amount of CO2,causing economic and environmental problems.Compared with the indirect method,the direct one-step conversion of CH4to CH3OH simplifies the reaction steps,avoids the high energy consumption step of converting CH4to synthesis gas,and reduces the reaction cost.Therefore,the direct conversion of CH4to CH3OH has great prospects for development.However,it is still very difficult to directly convert CH4into CH3OH under mild conditions at normal temperature and pressure due to the self-stability of CH4molecules.It is reported that the conversion of CH4to CH3OH can be carried out in strong acidic medium(such as oleum)or at high pressure(20~70 bar )[32⇓~34][31,35⇓~37]。 For example,Periana et al.Realized the selective conversion of CH4to CH3OH by the formation of methyl sulfate(CH3OSO3H)intermediate in a homogeneous system of oleum[32]。 Hutchings et al.Reported that Au-Pd colloid could selectively convert CH4to CH3OH under the conditions of reaction system pressure of 30 bar and 50℃,and the selectivity of CH3OH was as high as 92%[37]。 The above studies show that low temperature conditions are more conducive to avoid excessive oxidation of CH3OH to CO or CO2.Although many catalysts and catalytic systems have been developed,this reaction still has the problems of difficult C—H activation and easy peroxidation of CH3OH,which requires direct and selective conversion under harsh conditions.Therefore,it is necessary to develop new technologies to achieve the conversion of CH4to CH3OH under milder conditions 。
Photocatalysis is a green and promising technology,which uses photoinduced carriers to activate stable chemical bonds in advance,which can reduce the activation energy barrier and drive thermodynamically unfavorable chemical reactions[38⇓~40]。 For example,water(H2O)cleavage,CO2reduction,and CH4conversion,etc[41,42][43⇓~45][46,47]。 It has been reported that CH4can be converted into CH3OH at room temperature and normal pressure.For example,Sun and Xie et al.Reported that photocatalytic direct conversion of CH4to CH3OH was achieved ZnO/Fe2O3at 25°C and 1 bar,resulting in 100%selectivity of CH3OH and CH3OOH[48]。 Based on this,photocatalytic technology can be used to realize the direct conversion of CH4to CH3OH with high efficiency and selectivity under mild conditions.However,through the calculation of the equilibrium conversion yield of photocatalytic methane to methanol in the reported work,theoretically,the maximum equilibrium conversion yield of photocatalytic CH4to CH3OH is about 13.5%,which is still at a low level[25,49,50]。 Therefore,CH4conversion and CH3OH selectivity are still the major scientific issues of concern in the study of photocatalytic direct conversion of CH4to CH3OH 。
Aiming at the problems of low conversion rate of the CH4and low selectivity of the CH3OH,In this paper,the recent research ideas for improving CH4conversion and CH3OH selectivity in photocatalytic direct conversion of CH4to CH3OH,as well as the corresponding catalyst design strategies,are summarized.To improve the conversion rate of CH4,the main research idea is to effectively activate CH4by improving active oxygen radicals and catalytic activation pathways.To improve the selectivity of CH3OH,the main research idea is to inhibit the peroxidation of CH3OH and realize the regeneration of CH3OH.And the CH4conversion and the CH3OH selectivity are improved through catalyst design strategies such as loading of a cocatalyst,regulation of the size of the catalyst,construction of oxygen vacancies and the like.This review aims to promote the development of photocatalytic methane conversion technology and provide guidance for the design of efficient and selective photocatalysts 。

2 Improving CH4 conversion rate

Under illumination,the photocatalyst is excited to generate photogenerated electrons and photogenerated holes（h+）,which react with oxidants(such as O2,H2O2,H2O,CO2,etc.)in the reaction system.Promote the generation of reactive oxygen radicals(e.g.,hydroxyl radical and superoxide radical)and promote CH4activation[49,51⇓⇓~54]。 In fact,photogenerated holes can also directly catalyze and activate the C—H bond of CH4to form∙CH3.In addition,some active sites are formed on the surface of photocatalyst under illumination due to the migration and aggregation of photogenerated charges,which can also activate the C—H bonds of CH4[7,55,56]。 According to the mode of C—H bond activation of CH4,the improvement of CH4conversion can be divided into two categories:active oxygen radical activation and catalytic activation 。

2.1 Active oxygen radical activation

Hydroxyl radical(∙OH)and superoxide radical(∙O2−)are the most common active oxygen radicals in the photocatalytic CH4direct conversion to CH3OH reaction system[49,57,58]。 ∙OH and∙O2−have strong oxidizing properties and can attack the C—H bond of CH4to generate methyl radical(∙CH3).The∙CH3is directly combined with·OH generated in the reaction process to generate CH3OH,or is combined with·OOH to generate CH3OOH,and one O atom in the CH3OOH is further removed to generate CH3OH,as shown in formula(1 )[47]。 Therefore,the formation and concentration of∙OH and∙O2−reactive oxygen radicals are the key factors affecting the activation of the C—H bond of CH4 。

2.2 Catalytic activation

The photogenerated holes and the active sites on the surface of the photocatalyst play a crucial role in the catalytic conversion of CH4.The photogenerated holes and the active sites on the surface of the photocatalyst can weaken and destroy the C—H bonds in the CH4.Recently,Shi and Zhang et al reported that the Zn+-O−site formed by ZnO under illumination can activate the C—H bond of CH4to form a methyl intermediate（*CH3）[59]。 Typical active sites include oxygen vacancies(Ov),metal ions(M+)or lattice oxygen active species(O−),etc[60⇓⇓⇓⇓~65]。 CH4is adsorbed and activated at the active sites of the catalyst,allowing cleavage of the C—H bond to give·CH3.The reaction path of CH4conversion to CH3OH is shown in formula(2):
CH4+∙OH/∙O2−→∙CH3+∙OH/∙OOH→CH3OH
CH4+M+/O−/ h+/Ov→∙CH3+∙OH→CH3OH
Based on this,reactive oxygen radicals,h+,and active sites are critical for the activation of CH4.To regulate the conversion rate of CH4,it is necessary to regulate the production of reactive oxygen radicals of∙OH and∙O2−,or to regulate the production and active site of h+.In addition,reaction intermediates such as∙CH3,∙OH,and∙OOH are critical for the generation of CH3OH.To regulate the selectivity of CH3OH,the reaction intermediates such as∙CH3,∙OH and∙OOH need to be regulated in the reaction process 。

3 Design Strategy of Catalytic Materials for Improving CH4 Conversion

In order to solve the problem of low conversion rate of CH4,the catalytic material design can be used to improve the activation of active oxygen radicals and the catalytic activation path,and then improve the conversion rate of CH4 。

3.1 Active oxygen radical activation

Active oxygen radicals are usually closely related to the separation efficiency of photogenerated carriers,and the catalyst design strategy of loading metal cocatalyst and controlling the size of catalytic materials can be used to promote the generation of radicals,thereby improving the conversion rate of CH4[66]。

3.1.1 Supported cocatalyst

The cocatalyst(such as Au,Ag,Pd,etc.)can usually act as an active site or adjust the surface charge density of the photocatalyst to promote the activation of H2O,O2,H2O2,etc.In the reaction system to produce∙OH and∙O2−,thereby promoting the C—H bond activation of CH4[57,67⇓⇓~70]。 For example,Zhang and Wu et al.Reported that Cs0.33WO3supported graphitic phase carbon nitride(g-C3N4)activated O2to produce·O2−,The·O2−activates the CH4to generate∙CH3,∙CH3reacts with H2O to form CH3OH[57]。 The copper-modified carbon nitride polymer material(Cu/PCN)reported by Wang et al.Can generate H2O2in situ in a reaction system with pure water as a solvent under anaerobic and light conditions,and promote the decomposition of H2O2to generate·OH,thereby promoting the oxidation of CH4,and the generation of CH3OH and ethanol(Figure 1 )[67]。 This indicates that the supported cocatalyst regulates the production of∙OH and∙O2−to promote the C—H activation of CH4,which in turn increases the conversion of CH4 。
图1 Cu/PCN光催化直接转化CH4制CH3OH的反应机理图[67]

Fig. 1 The mechanism for photocatalytic methane conversion over Cu/PCN[67]. Copyright 2019, Nature

3.1.2 Regulating the size of catalyst

the size of the catalyst has a great influence on the catalytic performance.Small-sized catalysts can promote the catalytic reaction more effectively due to their higher specific surface area,more surface active sites and more effective spatial transport characteristics,which is conducive to promoting the generation of active radicals[66,71,72]。 In the reaction of photocatalytic direct conversion of CH4to CH3OH,the generation of active oxygen radicals can be promoted by controlling the size of the catalytic material,which can effectively promote the activation of CH4.For example,Han and Tang et al.Prepared quantum-sized BiVO4（q-BiVO4）and submicron-sized BiVO4（s-BiVO4）photocatalytic materials,and their photocatalytic performance in the direct conversion of CH4to CH3OH reaction showed that:q-BiVO4exhibited higher photocatalytic performance than s-BiVO4,indicating higher activation and conversion efficiency of CH4in the q-BiVO4reaction system[66]。 The reaction mechanism is that the：q-BiVO4oxidizes the H2O to generate OH under the condition of illumination,and the OH can attack the CH4to generate∙CH3,The∙CH3is combined with the O2and the H+to generate the CH3OOH,The CH3OOH further removes oxygen atoms to produce CH3OH.This indicates that the size of the catalytic material has a significant effect on the catalytic performance,and the activation efficiency of the CH4can be significantly improved by controlling the size of the catalytic material 。

3.2 Catalytic activation

3.2.1 Supported cocatalyst

The cocatalyst plays an important role in promoting the separation of electrons and holes,reducing their recombination rate,and acting as a surface reaction site.Therefore,loading cocatalyst on the matrix photocatalytic material is an effective means to promote the activation of reaction substrate molecules.The metal co-catalyst has a significant effect on the activation of CH4molecules in photocatalytic reactions.Commonly used metal promoters are Fe-based,precious metals(such as Au,Ag,Pd,etc.),and Cu-based promoters[11][47,73][67]。 For example,Ma and Tang et al.Reported that photogenerated holes generated on the surface of TiO2can directly activate CH4to form a∙CH3intermediate,And the activation efficiency of the CH4is improved by loading a cocatalyst FeOxon the TiO2and regulating and controlling an energy band structure and promoting the separation of photogenerated charges,so that the conversion rate of the CH4is up to 15%[49]。 However,Ordomsky and Khodakov et al.Found that in the Ag-heteropolyacid-TiO2（Ag-HPW/TiO2）photocatalytic CH4conversion reaction system,the Ag+of the cocatalyst Ag can be used as an active site to promote the effective activation of CH4[74]。 Meanwhile,Xie and Wang et al.Reported that the dimeric Cu promoter was supported on carbon nitride（C3N4）materials,and the dimeric Cu promoter could be used as an active site to effectively promote the activation of CH4to generate∙CH3（Fig.2 )[75]。 These studies demonstrate that the supported metal co-catalyst strategy can promote the activation of CH4by regulating the separation efficiency of surface photogenerated charges and surface active sites 。
图2 Cu2@C3N4光催化CH4+O2转化示意图[75]

Fig. 2 The Schematic diagram of Cu2@C3N4 photocatalytic CH4+O2 conversion[75]. Copyright 2022, Nature

3.2.2 Structural oxygen vacancy

In the photocatalytic reaction,the Oxygen vacancies on the surface of photocatalytic materials have two main effects.oxygen vacancies can not only act as carrier separation centers,but also further promote the separation and migration of carriers[76]。 Oxygen vacancies can also increase the unsaturated coordination sites on the surface of catalytic materials,which are beneficial to the adsorption and activation of reaction substrate molecules,such as CH4and O2）[61,76,77]。 Therefore,the construction of oxygen vacancies can generally improve the photocatalytic activity in photocatalytic reactions.In recent years,it has been found that the construction of oxygen vacancies on the surface of photocatalytic materials can promote the activation of CH4molecules in the photocatalytic direct conversion of CH4to CH3OH 。
It has been reported that oxygen vacancies on the surface of TiO2not only improve the separation of photogenerated carriers and promote the activation of CH4and H2O to generate∙CH3and∙OH,but also further promote the conversion of CH4[76]。 In addition,Wang and Zhou et al.Constructed oxygen vacancies on the surface of BiOCl catalytic materials,and found that the oxygen vacancies and the induced electron capture Bi atoms near the oxygen vacancies formed a bifunctional reaction center,which strongly adsorbed and activated CH4and O2,respectively[61]。 Then,the activated oxygen species∙O2−attacks the C—H bond of CH4,thus promoting the activation of CH4.Through density functional theory(DFT)calculations,Song and Ye et al.Found that oxygen vacancies were easily formed on the Au-ZnO/TiO2hybrid under illumination,which further promoted the dissociation of O2by reducing the adsorption energy and activation barrier,thus promoting the oxidation of CH4[78]。 The above results show that the formation of oxygen vacancies on the surface of catalytic materials can increase the active sites on the surface of catalytic materials and promote the separation of photogenerated carriers,thus improving the efficiency of CH4activation.This strategy can effectively promote CH4activation 。
Based on this,oxygen vacancies can be constructed to form more active sites on the surface of catalytic materials to promote the adsorption and activation of CH4,thereby improving the conversion rate of CH4 。

4 Improving CH3OH selectivity

In order to solve the problem of low selectivity of CH3OH in the photocatalytic direct conversion of CH4to CH3OH,inhibiting the peroxidation of CH3OH in the reaction is considered to be an effective way.This is a research idea that is generally recognized and recognized.There is another way to improve the selectivity of CH3OH.After the continuous dehydrogenation of CH3OH,the peroxidation products(such as HCHO)combine with the protons in the reaction system,thus realizing the regeneration of CH3OH in the reaction process 。

4.1 Inhibition of CH3OH peroxidation

Intermediates such as∙CH3,peroxymethyl radical(∙OOCH3),methoxy radical(∙OCH3),or methoxy radical(CH3O*)may be generated during the activation of CH4[25,50,66,79,80]。 These intermediates can react with water(H2O)or reactive oxygen intermediates such as hydroxyl radical(·OH),superoxide radical(·O2−),peroxyl hydroxyl radical(·OOH),etc.,to further generate CH3OH.Therefore,these intermediates play a crucial role for the selective generation of CH3OH 。
Zhou et al.Found that CH4could be activated on the surface of metal oxides and combined with lattice oxygen of metal oxides to form CH3O*in the process of photocatalytic direct conversion of CH4to CH3OH by metal oxides[50,81]。 The cleavage of different chemical bonds in CH3O*has a significant impact on the conversion pathway of CH4,and then has an important impact on the selectivity of CH3OH.Through in situ diffuse reflectance infrared spectroscopy and18O isotope labeling technology,the dynamic detection of the bond breaking process of the key intermediate CH3O*chemical bond was realized for the first time(Fig.3A–C),and it was found that the CH3O*intermediate would break the metal—O bond on the surface of ZnO,while the C—O bond would be broken on the surface of Ga2O3.The conversion process of the CH3O*intermediate on the ZnO and Ga2O3surfaces is shown in Fig.3D:the CH3O*intermediate on the ZnO surface breaks the metal—O bond to form the CH3O·intermediate.Formaldehyde(HCHO)is the main product of the reaction between the CH3O·intermediate and·OH.While the CH3O*intermediate on the surface of Ga2O3cleaves the C—O bond to form the CH3·intermediate.The major product from the reaction of the CH3·intermediate with·OH is CH3OH.Based on this,Ga2O3exhibited a higher CH3OH generation rate(325.4μmol·g-1·h-1)and selectivity(87.0%).In addition,the above study also found that by controlling the lattice oxygen mobility of metal oxides,electrons can be transferred from the surface of photocatalytic materials to CH3O*,and be directionally injected into the antibonding orbital of C—O bond to selectively break it.This study shows that the design of catalysts and the regulation of intermediates in the reaction process are very important to inhibit the peroxidation of CH3OH 。
图3 光照条件下，Ga2O3光催化(a) CH4+H2O、(b) CH4+H218O和(c) CH4+D2O混合物的原位漫反射红外光谱(in situ DRIFTS)图，(d) CH3O*在ZnO和Ga2O3表面的转化路径图[50]

Fig. 3 In situ DRIFTS spectra of Ga2O3 photocatalytic (a) CH4+H2O, (b) CH4+H218O and (c) CH4+D2O mixtures under light conditions. (d) Conversion path of CH3O* on ZnO and Ga2O3 surfaces[50]. Copyright 2023, ACS

At present,the strategies to inhibit the overoxidation of CH3OH mainly include supported co-catalyst and crystal face regulation 。

4.1.1 Supported promoter strategy

The metal co-catalyst can be used as the active site of CH4,or to promote the separation of photogenerated carriers,or as the active site of co-reactant(such as O2or H2O)in the reaction of direct conversion of photocatalytic CH4to CH3OH.By controlling the generation of an intermediate for generating the CH3OH,the reaction path is regulated and controlled,the peroxidation of the CH3OH is further inhibited,and the selectivity of the CH3OH is improved.In order to inhibit the peroxidation reaction of CH3OH,the strategies of supporting metal cocatalyst can be divided into the following three types:supporting single metal cocatalyst,supporting bimetallic cocatalyst and regulating the size of cocatalyst[47,82,83][25,84][85]。
(1)supported single metal co-catalyst
A monometallic cocatalyst is loaded on the catalytic material,and the generation of a reaction intermediate for generating CH3OH is controlled by regulating and controlling the activation process of a coreactant O2or H2O,so that the occurrence of an overoxidation reaction of the CH3OH is inhibited,and the selectivity is regulated and controlled.For example,Yang,Liu,and Zhai et al.Reported that Co promoter was supported on carbon nitride and formed an asymmetric coordination Co active site（AC-Co1/PCNKOH）with it,which regulated the single electron transfer process of H2O oxidation.The formation of OH*on AC-Co1/PCNKOHinhibits the peroxidation of CH3OH,thus improving the selectivity of CH3OH,which reaches 87.22%[82]。 In addition,Meng and Ye et al.Inhibited the overoxidation of CH3OH by loading noble metal cocatalyst on ZnO and acting as the activation site of O2to activate O2to·OOH intermediate,which reacted with·CH3to produce CH3OOH[47]。
(2)supported bimetallic cocatalyst
The double co-catalyst can effectively activate the co-reactant and regulate the reaction process through the regulation of double sites,thereby inhibiting the peroxidation reaction of the CH3OH and improving the selectivity.For example,Meng,Wang and Ye et al.Found that Au/CoOx/TiO2materials could selectively catalyze the conversion of CH4to CH3OH at room temperature[25]。 During the reaction,CoOxregulates the TiO2band structure,which inhibits the formation of highly oxidizing∙OH and prevents the further oxidation of the product CH3OH to HCHO and CO2.At the same time,photogenerated holes activate CH4to produce∙CH3,which reacts with∙OOH activated by Au co-catalyst to realize the selective conversion of CH4to CH3OH.After 2 H of reaction,the selectivity of the generated CH3OH reached 95%.Tang et al.Reported that Au-Cu dual co-catalyst was modified on ZnO to activate O2by Cu co-catalyst to produce∙OOH and activate H2O by Au co-catalyst to decompose into∙OH[84]。 The selective generation of CH3OH is promoted by the synergistic effect of Au-Cu dual co-catalyst,as shown in Fig.4 。
图4 ZnO、Au-ZnO、Cu-ZnO和AuCu-ZnO光催化CH4直接转化制CH3OH的性能图，AuCu-ZnO光催化CH4直接转化制CH3OH的反应机理图[84]

Fig. 4 Photocatalytic direct conversion of CH4 to CH3OH performance of ZnO, Au-ZnO, Cu-ZnO and AuCu-ZnO, and reaction mechanism diagram of AuCu-ZnO photocatalytic direct conversion of CH4 to CH3OH[84]. Copyright 2021, ACS

(3)loading metal promoters of different sizes
Generally speaking,the smaller the size of the cocatalyst,the larger its specific surface area,which can provide more active sites,thereby improving the activity of the photocatalytic reaction.In fact,the size of the co-catalyst may also affect the steric hindrance,affect the adsorption configuration of the reaction molecules on its surface,and then affect the reaction path and product selectivity[16]。 Tang et al.Found that by controlling the size of Au co-catalyst,the reaction path and radical type can be regulated,and then the selectivity of products can be affected[85]。 The principle is that the adsorption configuration of the O2on the In2O3（Au1/In2O3）loaded with Au single atoms and the In2O3（AuNPs/In2O3）loaded with Au nanoparticles is different,This results in the generation of·OOH from O2upon activation on Au1/In2O3and·OH upon activation on AuNPs/In2O3.Therefore,the reaction paths and main products of Au1/In2O3and AuNPs/In2O3in photocatalytic CH4conversion have significant differences.The specific reaction mechanism is as follows:On Au1/In2O3,·OOH generated after activation of O2reacts with·CH3to form CH3OOH,followed by overoxidation to form HCHO,the main product of which is HCHO.While on AuNPs/In2O3,the·OH generated after activation of O2reacts with·CH3to form CH3OH,Moreover,the peroxidation of CH3OH was inhibited,and the main product was CH3OH.After 3 H of reaction,the selectivity of CH3OH was as high as 89.42% 。

4.1.2 Crystal face control

different crystal planes of photocatalytic materials have different atomic structures,electronic structures and surface defects,which lead to different band gaps,conduction band positions and surface adsorption properties of photocatalytic materials,thus affecting their carrier separation efficiency and photocatalytic performance,and even affecting the reaction path[86,87]。 For example,Feng and Ye et al.Effectively regulated the intermediates generated in the reaction of CH4conversion to CH3OH by regulating the crystal faces of TiO2photocatalytic materials and exposing the crystal faces containing oxygen vacancies,thereby improving the selectivity of CH3OH[62]。 The reaction process of TiO2{001}crystal face selective photocatalytic direct conversion of CH4to CH3OH is shown in Fig.5.The oxygen vacancy on the{001}facet of TiO2can react with O2to form Ti-(OO)intermediate.Under illumination,Ti-(OO)will form Ti-O·active sites.Ti-O·reacts with CH4to form CH3O-Ti-OH or OH-Ti and Ti-OCH3intermediates.This process effectively inhibited the formation of·CH3and·OH,which in turn inhibited the peroxidation of CH3OH and improved the selectivity of CH3OH 。
图5 TiO2的{001}晶面上光催化CH4直接转化制CH3OH的反应过程图[62]

Fig. 5 The mechanism for photocatalytic conversion of CH4 to CH3OH over TiO2{001}[62]. Copyright 2021, Nature

4.2 Realize CH3OH regeneration

In the process of photocatalytic direct conversion of CH4to CH3OH,in order to improve the selectivity of CH3OH,in addition to inhibiting the peroxidation reaction,a new idea can be adopted,that is,the peroxidation product generated in the reaction process can be combined with protons again to realize the regeneration of CH3OH 。
Recently,Zhou et al.Found that O2was activated on the surface of BN to form oxygen active sites,and CH4was activated on the surface of BN to form H-N-B-OCH3intermediate(Fig.6 )[88]。 During the reaction,the N—H bond can act as a"hydrogen bond trap"to capture electrons and induce the cleavage of C—H in the N—H substitution target products CH3OH and HCHO,thus avoiding the continuous dehydrogenation process.Interestingly,after the cleavage of the N—H bond on the BN surface,the released proton will be attracted and captured by HCHO,resulting in a"proton backtracking"process to regenerate CH3OH.Benefiting from the combined effect of"hydrogen bond trap"and"proton backtracking",the selectivity of BN photocatalytic CH4conversion to CH3OH and HCHO is up to 100% 。
图6 光催化CH4转化机理. (a) 典型的催化剂的表面反应；(b) BN的表面反应[88]

Fig. 6 Proposed mechanism. for photocatalytic conversion of methane. (a) Typical surface reaction of the catalyst, and (b) the BN surface[88]. Copyright 2023, Wiley

This study breaks the traditional thinking of inhibiting excessive oxidation of products,proposes a new reaction mechanism of proton backtracking,and realizes the regeneration of methanol.This finding provides a new solution to the difficult problem of over-oxidation of the target product CH3OH in the photocatalytic CH4direct conversion process 。

5 Conclusion and prospect

CH4is not only used as fuel for combustion,but also an important raw material for the synthesis of C1 chemicals.Among them,CH3OH is one of the ideal products of CH4conversion.However,the CH4molecule has a stable tetrahedral structure,and the activation energy of the C—H bond is very high,which makes it difficult for the CH4molecule to be catalytically oxidized.Compared with the traditional thermal catalytic technology,the photocatalytic technology breaks the thermodynamic equilibrium and realizes the conversion of CH4under mild conditions.However,in the photocatalytic conversion of CH4to CH3OH,there is still the problem of peroxidation of CH4and the peroxidation of reaction products.Therefore,the selective activation and directional transformation of CH4have become a hot research topic.To solve this problem,a large number of studies have found that the activation and conversion of CH4can be regulated by controlling the key intermediates produced in the reaction process.However,there are still some problems to be solved about the precise regulation of key intermediates in the reaction process and the efficient and selective photocatalytic conversion of CH4to CH3OH 。
(1)to study the reaction mechanism.According to the summary of photocatalytic CH4conversion to CH3OH in recent years,the key intermediate produced in the reaction process plays a vital role in the formation of CH3OH and its selectivity.In order to improve the product selectivity,the regulation of these key intermediates is particularly important.However,at present,the specific precise regulation of key intermediates is still not clear enough,and more research is needed to explore from the atomic and electronic levels 。
(2)Development of in-situ characterization techniques.To explore the regulation of key intermediates during CH4conversion,we first need to capture the key intermediates generated during the reaction.At present,the reported photocatalytic conversion of CH4to CH3OH is usually carried out in the gas-liquid phase.However,there are some difficulties in monitoring the reaction process in liquid phase system.At present,in situ electron paramagnetic resonance(EPR)can be used to capture reaction intermediates(∙OH,∙OOH and in situ EPR),while in situ FTIRS and in situ ART-FTIRS can be used to monitor the intermediates formed during the reaction.However,the solubility of methane molecules in water is very low,and the signals of some intermediate substances in the reaction process are weak,which brings great difficulties to the analysis of the reaction process.In addition,some reported works on photocatalytic conversion of CH4to CH3OH will exert a certain pressure on the reaction system,which makes it difficult to detect the reaction process by in-situ detection technology.In order to better capture and detect the intermediates in the reaction process by in situ technology and analyze the reaction process more accurately,it is necessary to improve the reaction device of in situ detection technology to keep it consistent with the working conditions 。
In addition,ultrafast spectroscopy,as an effective tool to study the photocatalytic kinetic process,has not been fully utilized,so it should attract more attention and attention。
(3)Design photothermal catalytic materials.Although the activation efficiency of CH4can be improved to some extent by manipulating the photocatalytic materials to control the formation of intermediates and thus manipulate the photocatalytic process,it is still a challenge to realize the wide application of photocatalytic CH4direct conversion technology to CH3OH in industrial production.In some reported works,the conversion efficiency of CH4can be improved more efficiently by external temperature.In addition,the coupling of light and heat,that is,through the synergistic effect of light and heat,can also improve the efficiency of CH4conversion.For the heat required in the reaction process,the required photothermal synergy can be provided by the thermal effect generated by light.However,a large amount of heat from infrared light in solar energy(solar thermal effect)is often ignored,resulting in a large waste of solar energy.Through photothermal catalytic materials,the solar thermal effect can be fully utilized,and the solar catalytic efficiency can be significantly improved through photothermal synergistic catalysis.Further research and improvement are needed to solve this problem because of the low photocatalytic efficiency of photocatalytic technology 。
(4)Design a suitable reaction system.In a closed system,the continuous accumulation of products will lead to the aggravation of peroxidation and the inability to carry out large-scale reactions.Therefore,the flow system has the advantages of timely product separation and large batch reaction.The current flow systems used for CH4conversion mainly include gas-solid flow bed reactors.However,the photocatalytic direct conversion of CH4to CH3OH involves a gas-liquid-solid three-phase reaction.In the design of flow system,the design of gas-liquid-solid three-phase system should be considered,and other types of reactors such as fluidized bed reactor,membrane reactor and fluidized reactor are also worth considering 。
To sum up,although there are great challenges in photocatalytic CH4conversion to CH3OH,it is very promising to use photocatalytic CH4conversion to CH3OH with high efficiency and high selectivity through the regulation of photocatalytic materials and the adjustment of temperature and pressure,even for industrial development 。

References

Publishing order | Descend order by publishing year | Descend order by cited within
[1]
Sher Shah M S A, Oh C, Park H, Hwang Y J, Ma M, Park J H. Adv. Sci., 2020, 7(23): 2001946.

[2]
Amano F, Akamoto C, Ishimaru M, Inagaki S, Yoshida H. Chem. Commun., 2020, 56(47): 6348.

[3]
Wang J, Yao N. Prog. Chem., 2017, 29: 1509.

(王晶, 姚楠. 化学进展, 2017, 29: 1509.)

[4]
BP plc. BP Statistical Review of World Energy 2021. London: BP plc, 2021.

(英国石油公司. BP世界能源统计年鉴2021. 伦敦: 英国石油公司, 2021.)

[5]
Holmen A. Catal. Today, 2009, 142(1/2): 2.

[6]
Yuniar G, Saputera W H, Sasongko D, Mukti R R, Rizkiana J, Devianto H. Molecules, 2022, 27(17): 5496.

[7]
Yuliati L, Yoshida H. Chem. Soc. Rev., 2008, 37(8): 1592.

[8]
Li Q, Ouyang Y, Li H, Wang L, Zeng J. Angew. Chem. Int. Ed., 2022, 61: e202108069.

[9]
Gunsalus N J, Koppaka A, Park S H, Bischof S M, Hashiguchi B G, Periana R A. Chem. Rev., 2017, 117(13): 8521.

[10]
Natte K, Neumann H, Beller M, Jagadeesh R V. Angew. Chem. Int. Ed., 2017, 56(23): 6384.

[11]
An B, Li Z, Wang Z, Zeng X D, Han X, Cheng Y Q, Sheveleva A M, Zhang Z Y, Tuna F, McInnes E J L, Frogley M D, Ramirez-Cuesta A J, Natrajan L S, Wang C, Lin W B, Yang S H, Schröder M. Nat. Mater., 2022, 21(8): 932.

[12]
Boulamanti A, Moya J A. Renew. Sustain. Energy Rev., 2017, 68: 1205.

[13]
Hogerwaard J, Dincer I, Naterer G F, Patterson B D. Int. J. Energy Res., 2019, 43(11): 5687.

[14]
Tabibian S S, Sharifzadeh M. Renew. Sustain. Energy Rev., 2023, 179: 113281.

[15]
Zhou Y Y, Wang H P, Liu X C, Qiao S M, Shao D K, Zhou J, Zhang L, Wang W Z. Nano Energy, 2021, 79: 105449.

[16]
Zeng Y, Tang Z Y, Wu X Y, Huang A H, Luo X, Xu G Q, Zhu Y F, Wang S L. Appl. Catal. B Environ., 2022, 306: 120919.

[17]
Yang J, Hao J Y, Wei J P, Dai J, Li Y. Fuel, 2020, 266: 117104.

[18]
Tian Y D, Piao L Y, Chen X B. Green Chem., 2021, 23(10): 3526.

[19]
Sun H L, Hu L F, Li Z Y, Lang J Y, Wang C L, Liu X H, Hu Y H, Jin F M. ChemCatChem, 2022, 14(10): e202200001.

[20]
Yang Y, Chai Z, Qin X, Zhang Z, Muhetaer A, Wang C, Huang H, Yang C, Ma D, Li Q, Xu D. Angew. Chem. Int. Ed., 2022, 61: e202200567.

[21]
Cao S F, Zhang K, Hanna B, Al-Sayed E. Chin. Chemical Lett., 2022, 33(4): 1757.

[22]
Kwon Y, Kim T Y, Kwon G, Yi J, Lee H. J. Am. Chem. Soc., 2017, 139(48): 17694.

[23]
Zuo Z J, Ramírez P J, Senanayake S D, Liu P, Rodriguez J A. J. Am. Chem. Soc., 2016, 138(42): 13810.

[24]
Jørgensen M, Grönbeck H. ACS Catal., 2016, 6(10): 6730.

[25]
Song H, Meng X G, Wang S Y, Zhou W, Song S, Kako T, Ye J H. ACS Catal., 2020, 10(23): 14318.

[26]
Cheng F Y, Duan X Y, Xie K. Angew. Chem., 2021, 133(34): 18940.

[27]
Bai S X, Liu F F, Huang B L, Li F, Lin H P, Wu T, Sun M Z, Wu J B, Shao Q, Xu Y, Huang X Q. Nat. Commun., 2020, 11: 954.

[28]
Sushkevich V L, Palagin D, Ranocchiari M, van Bokhoven J A. Science, 2017, 356(6337): 523.

[29]
Lu J, Guo Y, Liu Q, Han G, Wang Z J. Prog. Chem., 2017, 29: 1471.

(卢君颖, 郭禹, 刘其瑞, 韩广智, 王周君. 化学进展, 2017, 29: 1471.)

[30]
Olivos-Suarez A I, Szécsényi À, Hensen E J M, Ruiz-Martinez J, Pidko E A, Gascon J. ACS Catal., 2016, 6(5): 2965.

[31]
Qi G D, Davies T E, Nasrallah A, Sainna M A, Howe A G R, Lewis R J, Quesne M, Catlow C R A, Willock D J, He Q, Bethell D, Howard M J, Murrer B A, Harrison B, Kiely C J, Zhao X L, Deng F, Xu J, Hutchings G J. Nat. Catal., 2022, 5(1): 45.

[32]
Periana R A, Taube D J, Evitt E R, Löffler D G, Wentrcek P R, Voss G, Masuda T. Science, 1993, 259(5093): 340.

[33]
Periana R A, Taube D J, Gamble S, Taube H, Satoh T, Fujii H. Science, 1998, 280(5363): 560.

[34]
Hashiguchi B G, Bischof S M, Konnick M M, Periana R A. Acc. Chem. Res., 2012, 45(6): 885.

[35]
Jin Z, Wang L, Zuidema E, Mondal K, Zhang M, Zhang J, Wang C T, Meng X J, Yang H Q, Mesters C, Xiao F S. Science, 2020, 367(6474): 193.

[36]
Hammond C, Forde M M, Ab Rahim M H, Thetford A, He Q, Jenkins R L, Dimitratos N, Lopez-Sanchez J A, Dummer N F, Murphy D M, Carley A F, Taylor S H, Willock D J, Stangland E E, Kang J, Hagen H, Kiely C J, Hutchings G J. Angew. Chem. Int. Ed., 2012, 51(21): 5129.

[37]
Agarwal N, Freakley S J, McVicker R U, Althahban S M, Dimitratos N, He Q, Morgan D J, Jenkins R L, Willock D J, Taylor S H, Kiely C J, Hutchings G J. Science, 2017, 358(6360): 223.

[38]
Li X Y, Wang C, Tang J W. Nat. Rev. Mater., 2022, 7(8): 617.

[39]
Shoji S, Peng X B, Yamaguchi A, Watanabe R, Fukuhara C, Cho Y, Yamamoto T, Matsumura S, Yu M W, Ishii S, Fujita T, Abe H, Miyauchi M. Nat. Catal., 2020, 3(2): 148.

[40]
Song H, Meng X G, Wang Z J, Liu H M, Ye J H. Joule, 2019, 3(7): 1606.

[41]
Xiang X L, Zhu B C, Cheng B, Yu J G, Lv H J. Small, 2020, 16(26): 2001024.

[42]
He J R, Hu L J, Shao C T, Jiang S J, Sun C Z, Song S Q. ACS Nano, 2021, 15(11): 18006.

[43]
Cao Y H, Guo L, Dan M, Doronkin D E, Han C Q, Rao Z Q, Liu Y, Meng J, Huang Z A, Zheng K B, Chen P, Dong F, Zhou Y. Nat. Commun., 2021, 12: 1675.

[44]
Han C Q, Zhang R M, Ye Y H, Wang L, Ma Z Y, Su F Y, Xie H Q, Zhou Y, Wong P K, Ye L Q. J. Mater. Chem. A, 2019, 7(16): 9726.

[45]
Ran J R, Jaroniec M, Qiao S Z. Adv. Mater., 2018, 30(7): 1704649.

[46]
Wang J B, Huang Z A, Wang Y, Wu J D, Rao Z Q, Wang F, Zhou Y. Chin. Chemical Lett., 2022, 33(10): 4687.

[47]
Song H, Meng X G, Wang S Y, Zhou W, Wang X S, Kako T, Ye J H. J. Am. Chem. Soc., 2019, 141(51): 20507.

[48]
Zheng K, Wu Y, Zhu J C, Wu M Y, Jiao X C, Li L, Wang S M, Fan M H, Hu J, Yan W S, Zhu J F, Sun Y F, Xie Y. J. Am. Chem. Soc., 2022, 144(27): 12357.

[49]
Xie J, Jin R, Sankar G, Li A, Bi Y, Ruan Q, Deng Y, Ma D, Tang J. Nat. Catal., 2018, 1: 889.

[50]
Han C, Cao Y, Yu W, Huang Z, Dong F, Ye L, Yu S, Zhou Y. J. Am. Chem. Soc., 2023, 145: 8609.

[51]
Cao Y H, Guo R, Ma M Z, Huang Z A, Zhou Y. Acta Phys. Chim. Sin., 2023: 2303029.

[52]
Nosaka Y, Nosaka A Y. Chem. Rev., 2017, 117(17): 11302.

[53]
Gan Y P, Huang M, Yu F, Yu X, He Z J, Liu J, Lin T J, Dai Y Y, Niu Q, Zhong L S. ACS Sustainable Chem. Eng., 2023, 11(14): 5537.

[54]
Cao Y, Huang Z, Han C, Zhou Y. Adv. Sci., 2024: 2306891.

[55]
Schwach P, Pan X L, Bao X H. Chem. Rev., 2017, 117(13): 8497.

[56]
Villa K, Galán-Mascarós J R. ChemSusChem, 2021, 14(9): 2023.

[57]
Li Y, Li J, Zhang G K, Wang K, Wu X Y. ACS Sustainable Chem. Eng., 2019, 7(4): 4382.

[58]
Gondal M A, Hameed A, Yamani Z H, Arfaj A. Chem. Phys. Lett., 2004, 392(4/6): 372.

[59]
Wang P, Shi R, Zhao Y X, Li Z H, Zhao J Q, Zhao J Q, Waterhouse G I N, Wu L Z, Zhang T R. Angew. Chem. Int. Ed., 2023, 62(23): e202304301.

[60]
Li L, Li G D, Yan C, Mu X Y, Pan X L, Zou X X, Wang K X, Chen J S. Angew. Chem. Int. Ed., 2011, 50(36): 8299.

[61]
Chen Y, Wang F, Huang Z A, Chen J H, Han C Q, Li Q L, Cao Y H, Zhou Y. ACS Appl. Mater. Interfaces, 2021, 13(39): 46694.

[62]
Feng N D, Lin H W, Song H, Yang L X, Tang D M, Deng F, Ye J H. Nat. Commun., 2021, 12: 4652.

[63]
Li K, Wang H, Wei Y, Ao X, Liu M. Prog. Chem., 2008, 20: 1306.

(李孔斋, 王华, 魏永刚, 敖先权, 刘明春. 化学进展, 2008, 20: 1306.)

[64]
He K, Shen R, Hao L, Li Y, Zhang P, Jiang J, Xin L. Acta Phys.-Chim. Sin., 2022, 38: 2201021.

(何科林, 沈荣晨, 郝磊, 李佑稷, 张鹏, 江吉周, 李鑫. 物理化学学报, 2022, 38: 2201021)

[65]
Zhu S, Li X D, Pan Z K, Jiao X C, Zheng K, Li L, Shao W W, Zu X L, Hu J, Zhu J F, Sun Y F, Xie Y. Nano Lett., 2021, 21(9): 4122.

[66]
Fan Y Y, Zhou W C, Qiu X Y, Li H D, Jiang Y H, Sun Z H, Han D X, Niu L, Tang Z Y. Nat. Sustain., 2021, 4(6): 509.

[67]
Zhou Y, Zhang L, Wang W. Nat. Commun., 2019, 10: 506.

[68]
Zhou W C, Qiu X Y, Jiang Y H, Fan Y Y, Wei S L, Han D X, Niu L, Tang Z Y. J. Mater. Chem. A, 2020, 8(26): 13277.

[69]
Zhang Z J, Zhang J, Zhu Y R, An Z, Shu X, Song H Y, Wang W L, Chai Z G, Shang C B, Jiang S J, Jing Y S, Zheng L R, He J. Chem Catal., 2022, 2(6): 1440.

[70]
Cao Y H, Yang Y T, Yu W, Li G, Rao Z Q, Huang Z A, Wang F, Yuan C D, Zhou Y. ACS Appl. Mater. Interfaces, 2022, 14(11): 13344.

[71]
Liu Y H, Zhang W, Zheng W T. Nano Micro Lett., 2022, 14(1): 158.

[72]
Abdelghafar F, Xu X M, Jiang S P, Shao Z P. Mater. Rep. Energy, 2022, 2(3): 100144.

[73]
Wang P, Shi R, Zhao J, Zhang T. Adv. Sci., 2023, 2305471.

[74]
Yu X, Zholobenko V L, Moldovan S, Hu D, Wu D, Ordomsky V V, Khodakov A Y. Nat. Energy, 2020, 5(7): 511.

[75]
Xie P F, Ding J, Yao Z H, Pu T C, Zhang P, Huang Z N, Wang C H, Zhang J L, Zecher-Freeman N, Zong H, Yuan D S, Deng S W, Shahbazian-Yassar R, Wang C. Nat. Commun., 2022, 13: 1375.

[76]
Luo P P, Zhou X K, Li Y, Lu T B. ACS Appl. Mater. Interfaces, 2022, 14(18): 21069.

[77]
Miao T J, Wang C, Xiong L Q, Li X Y, Xie J J, Tang J W. ACS Catal., 2021, 11(13): 8226.

[78]
Song S, Song H, Li L, Wang S, Chu W, Peng K, Meng X, Wang Q, Deng B, Liu Q. Nat. Catal., 2021, 4: 1032.

[79]
Lustemberg P G, Palomino R M, Gutiérrez R A, Grinter D C, Vorokhta M, Liu Z Y, Ramírez P J, Matolín V, Ganduglia-Pirovano M V, Senanayake S D, Rodriguez J A. J. Am. Chem. Soc., 2018, 140(24): 7681.

[80]
He Y L, Guo F C, Yang K R, Heinlein J A, Bamonte S M, Fee J J, Hu S, Suib S L, Haller G L, Batista V S, Pfefferle L D. J. Am. Chem. Soc., 2020, 142(40): 17119.

[81]
Han C Q, Cao Y H, Qiu J, Ma Z M, Dong F, Zhou Y. Chin. Sci. Bull., 2023, 68: 4544.

(韩春秋, 曹玥晗, 邱杰, 马敏智, 董帆, 周莹. 科学通报, 2023, 68: 4544.)

[82]
Ding J, Teng Z Y, Su X Z, Kato K, Liu Y H, Xiao T, Liu W, Liu L Y, Zhang Q, Ren X Y, Zhang J C, Chen Z Y, Teruhisa O, Yamakata A, Yang H B, Huang Y Q, Liu B, Zhai Y M. Chem, 2023, 9(4): 1017.

[83]
Luo L, Fu L, Liu H F, Xu Y X, Xing J L, Chang C R, Yang D Y, Tang J W. Nat. Commun., 2022, 13: 2930.

[84]
Luo L, Gong Z Y, Xu Y X, Ma J N, Liu H F, Xing J L, Tang J W. J. Am. Chem. Soc., 2022, 144(2): 740.

[85]
Jiang Y H, Li S Y, Wang S K, Zhang Y, Long C, Xie J, Fan X Y, Zhao W S, Xu P, Fan Y Y, Cui C H, Tang Z Y. J. Am. Chem. Soc., 2023, 145(4): 2698.

[86]
Bai Y, Chen T, Wang P Q, Wang L, Ye L Q. Chem. Eng. J., 2016, 304: 454.

[87]
Li H, Zhang L Z. Curr. Opin. Green Sustain. Chem., 2017, 6: 48.

[88]
Cao Y, Yu W, Han C, Yang Y, Rao Z, Guo R, Dong F, Zhang R, Zhou Y. Angew. Chem. Int. Ed., 2023, 62: e202302196.

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