image
Home Journals Progress in Chemistry
Progress in Chemistry

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

About  /  Aim & scope  /  Editorial board  /  Indexed  /  Contact  / 
Online first  /  Current issue  /  All issues  /  Top access  /  RSS

Progress in Chemistry >

2023 , Vol. 35 >Issue 12: 1752 - 1763

DOI: https://doi.org/10.7536/PC230415

Review

Research Progress in Synthesis of Titanium-Based Organic Framework Materials

  • Suhui Liu 1, 2 ,
  • Feifei Zhang 1, 2 ,
  • Xiaoqing Wang 1, 2 ,
  • Puxu Liu 1, 2 ,
  • Jiangfeng Yang , 1, 2, *
Expand
  • 1 College of Chemical Engineering and Technology, Taiyuan University of Technology,Taiyuan 030024, China
  • 2 Shanxi Key Laboratory of Gas Energy Efficient and Clean Utilization,Taiyuan 030024, China
*Corresponding author e-mail:

Received date: 2023-04-13

  Revised date: 2023-06-30

  Online published: 2023-09-10

Supported by

National Natural Science Foundation of China(21908153)

Fold

Abstract

As a kind of metal-organic framework (MOF) with high valence, titanium-based metal-organic framework (Ti-MOF) has superior chemical stability, appealing photoresponsive properties, low toxicity and so on. However, due to the high reactivity of titanium sources, it brings certain challenges to the synthesis of materials. In this paper, the research progress of Ti-MOF synthesis in recent years is reviewed, and the solvothermal synthesis, post-synthetic modification and in situ SBUs construction methods are introduced in detail. The topological types and crystal structures formed are analyzed, and the synthesis rules of Ti-MOF and the advantages and disadvantages of various methods are summarized. It is pointed out that the control of the metal source and coordination environment is the most important strategy to obtain Ti-MOF, and the construction of Ti-MOF by in-situ formation of SBUs and heterometallic Ti/M-MOF are prospected.

Contents

1 Introduction

2 Synthesis of Ti-MOF

2.1 Solvothermal synthesis

2.2 Post-synthetic modification

2.3 In situ SBUs construction methods

3 Conclusion and outlook

Key words： titanium-based MOFs; synthesis; solvothermal synthesis; post-synthetic modification

Cite this article

Suhui Liu , Feifei Zhang , Xiaoqing Wang , Puxu Liu , Jiangfeng Yang . Research Progress in Synthesis of Titanium-Based Organic Framework Materials[J]. Progress in Chemistry, 2023 , 35(12) : 1752 -1763 . DOI: 10.7536/PC230415

1 Introduction

Metal-organic framework (MOF) is one of the most popular materials nowadays, which is self-assembled by organic ligands and metal ions or clusters through coordination bonds. Compared with traditional porous materials,Because of its high porosity, large specific surface area (1000~10000 m2·g-1), low crystal density, regular pore channels, adjustable pore size and diverse topological structures, it has attracted wide attention of researchers and has been used in the fields of environment, energy and catalysis[1,2][3,4][5][6]. In the construction of MOF, almost all metal cations, including some radioactive cations, are used as inorganic nodes (Fig. 1)[7]. At present, the number of MOFs has exceeded 80,000, and MOF chemistry is booming exponentially.
图1 已被用作构建MOF的金属。橙色:已被使用;蓝色:未被使用[7]

Fig. 1 Metal that has been used to construct MOF. Orange: used; blue: unused[7]

In general,MOF can be composed of monovalent (Cu+, Ag+, etc.), divalent (Mg2+, Mn2+, Fe2+,Co2+ 、Ni2+ 、Cu2+ 、Zn2+ 、Cd2+, etc.), trivalent (U Al3+Sc3+ 、UV3+ UNCr3+Fe3+ 、UGa3+ UNIn3+Lanthanide) or tetravalent (Ti4+, U Zr4+ U N Hf4+ N K Ce4+ are cation architectures. Divalent metal cations such as Zn2+ and Cu2+ have been widely used in the synthesis of MOF. Despite their many advantages, low-valent metal MOF has a small coordination number, and the metal-oxygen bond formed is not strong enough and unstable under many conditions, which directly limits the application of this kind of MOF[8⇓~10]. Therefore, in recent years, researchers have devoted themselves to finding ways to improve the stability of MOF, and found that high-valence metal cations can form stronger coordination bonds and more stable frameworks with organic ligands such as carboxylates in the same coordination environment[11]. Group IV metal cations usually exist in the positive tetravalent oxidation state. When combined with carboxylate ligands, in addition to stronger coordination bonds, more ligands are needed to balance the charge, so the coordination number is higher, which prevents the attack of guest molecules such as water molecules and increases the stability of the framework, thus forming a stable MOF[12].
Among the MOFs constructed by tetravalent metals, Ti-MOF has shown incomparable advantages in the field of photocatalysis due to its special photoresponsiveness in addition to its diverse structure, large specific surface area, highly concentrated active sites, and tunable pores. The photoresponse property is a necessary element for the preparation of catalysts in photochemical reactions, and the sustainability of photocatalysts is also a major concern. As a widely used commercial photocatalyst, TiO2 has the main disadvantages that the band gap energy of TiO2 is very large, it can only be activated under ultraviolet irradiation, and the specific surface area, active sites and pore structure are difficult to control. However, Ti-MOF has special photoresponse characteristics, which can adjust the band gap and structure for specific photocatalytic reactions. This process will change the electronic structure, inhibit electronic recombination, and be conducive to the stability of the catalyst, thus achieving the sustainability of the photocatalyst. In addition, Ti-MOF is also characterized by low toxicity compared with TiO2. TiO2 is a widely used and commercialized material, but in 2020, the European Union listed inhalable titanium dioxide as a Class II suspected carcinogen, and the Chinese Academy of Sciences also proposed that nano-titanium dioxide materials can cause potential environmental pollution problems, while Ti-MOF has low toxicity and has been proved to replace the role of TiO2 in many fields[13][14,15].
Ti-MOF has attracted the intense attention of researchers to this new class of materials due to its excellent performance in the field of photocatalysis, and it has also been used in various fields, including gas separation, gas storage, catalysis and sensors (Table 1), and has broad application prospects. However, the focused Ti-MOF is limited to a few kinds, which is due to the "unpredictable" activity of titanium ions, making it difficult for researchers to effectively control its chemical properties and crystallization process. Therefore, the synthesis of Ti-MOF is more difficult than other metal MOFs. Up to now, there are very few kinds, accounting for only a small part of the MOF family (less than 0.1%).
表1 Ti-MOF的应用范围[11]

Table 1 Application fields of Ti-MOF[11]

MOF Ti-oxo-cluster Bandgap energy (eV) Application
MIL-125 Ti8O8(OH)4(CO2)16 3.60 Alcohol oxidation[18]
MIL-125-NH2 Ti8O8(OH)4(CO2)16 2.60 CO2 photoreduction, water splitting
H2 production[21]
NTU-9 TiO6 1.72 Dye degradation[17]
PCN-22 Ti7O6(CO2)12 1.93 Alcohol oxidation[19]
MOF-901 Ti6O6(CO2)6 2.65 Polymerization[22]
ZSTU-3 (Ti6O12)n 2.20 H2 production[23]
MUV-10 Ti2Ca2(O)2(H2O)4(CO2)8 3.10 H2 production[24]
MUV-101 [TiM2(O)
(O2C)6X3]
(M=Mg, Fe,
Co, Ni;)		 — Hydrolysis of nerve agent simulants[25]
FIR-125 Ti8O8(OH)4(CO2)16 2.95 CO2 photoreduction[26]
The fundamental reason is that the coordination number of Ti4+ in most titanium precursors is lower than the six-coordination number of TiO2, and the strong reactivity of Ti4+ with oxygen makes titanium precursors easy to hydrolyze or react with water to form amorphous TiO2.This will have a negative impact on the crystallization process of MOF, which is prone to form poor crystallinity samples such as sol, gel or amorphous powder, thus leading to great challenges in the synthesis of Ti-MOF[11][16]. In addition, titanium salts are highly reactive and can rapidly react with organic carboxylate ligands to form strong Ti — O bonds, which hinder the polymerization and dissociation of the bonds, resulting in the difficulty of producing crystalline Ti-MOF under common solvothermal conditions, and the synthesis conditions must be precisely controlled. Therefore, in recent years, researchers have focused on the synthesis control of Ti-MOF and the design of new structures, focusing on the control of various conditions in the synthesis process (pH environment, solvothermal conditions) and synthesis methods (solvothermal direct synthesis, in situ formation of SBUs construction, post-exchange synthesis), in order to expand the synthesis and application of Ti-MOF[17][18][18][19][20].
In this paper, the research progress in the synthesis of Ti-MOF is reviewed (Figure 2), the synthesis methods, topological types and crystal structures of Ti-MOF are introduced, the synthesis rules of Ti-MOF and the advantages and disadvantages of various synthesis methods are summarized, and some ideas for expanding the synthesis of Ti-MOF are put forward.
图2 Ti-MOF发展历程(橙色:溶剂热直接合成法;黄色:后交换合成法;绿色:原位生成SBUs构筑法)

Fig. 2 Development of Ti-MOF (Orange: solvothermal synthesis; yellow: post-synthetic modification; green: in situ SBUs construction method)

2 Ti-MOF synthesis method

2.1 Solvothermal synthesis of Ti-MOF

2.1.1 Solvothermal synthesis of monometallic Ti-MOF

Solvothermal method was mainly used in the early synthesis of Ti-MOF. The method is a synthesis method in which a titanium precursor and an organic ligand are placed in a closed system such as an autoclave, a liquid organic substance is used as a solvent, and parameters such as a titanium metal source, a solvent, temperature, reaction time and the like are reasonably optimized through a synthesis process to react to generate the Ti-MOF[27].
In 1999, F Férey et al. First synthesized MIL-22 through methylene diphosphonic acid and Ti-oxo cluster under solvothermal conditions, which is the first three-dimensional titanium-based MOF with open structural characteristics. Titanium octahedra and diphosphonic acid are interconnected to form a three-dimensional network, forming cross-linked ten-, seven- and six-membered ring tunnels along a, B and C axes, respectively[28]. In 2006, the research team connected the N, N '-piperazine dimethylene phosphonic acid ligand with Ti-oxo clusters to form the framework MIL-91, which exhibited permanent porosity and produced one-dimensional small pore channels capable of adsorbing nitrogen at 77 K, with Langmuir specific surface area close to 500 m2·g-1 and pore volume close to 0.19 cm3·g-1[29]. The material has a pore size of 44 Å and a strong polar phosphonic acid functionalized framework, which is suitable for capturing CO2, but its poor stability limits its further application.
The high reactivity of titanium metal salts with carboxylate ligands makes it difficult to form crystalline products, so it was not until 2009 that F Férey et al. Reported the first Ti-MOF based on carboxylate ligands (terephthalic acid), titanium isopropoxide (Ti(OiPr)4) in N,Dissolved in N '-dimethylformamide (DMF)/methanol and heated to 150 ℃ for 15 H, the obtained crystal is called MIL-125 (Fig. 3). MIL-125 has a rigid microporous structure with trapezoidal pore channels ranging from 5 to 77 Å in size, a specific surface area (BET) of 1550 m2·g-1, and a pore volume of 0.65 cm3·g-1[18]. It belongs to the body-centered tetragonal system, and its three-dimensional structure shows that its secondary structural units are ring-shaped clusters composed of Ti8O8, which are connected by carboxylic acid groups to form Ti8O8(OH)4(CO2)12 structural units with special spatial structure, thus forming crystals with fcu topology. Subsequently, the researchers further synthesized NH2-MIL-125 with the same structure as MIL-125 in the same solvent environment[21]. These two pioneering materials have opened up a new world of photocatalytic reactions using Ti-MOF[30].
图3 MIL-125的结构图[11]

Fig. 3 Structure of MIL-125[11]

In 2014, Zhang et al. Reported a new microporous Ti-MOF, NTU-9, which was heated at 120 ℃ for 5 days in the environment of glacial acetic acid, and the six coordination sites of Ti atoms were uniformly connected by three 2,5-dihydroxyterephthalic acids to form a two-dimensional layered structure[17]. The uncoordinated carboxyl O atoms between the layers form a three-dimensional framework through the formation of hydrogen bonds, forming a one-dimensional channel of about 11 Å × 11 Å along the C axis. The BET of NTU-9 at 77 K is 917 m2·g-1, which has a strong affinity for acetylene (C2H2) due to the presence of a large number of polar oxygen atoms on the surface of its one-dimensional channel.The adsorption capacity at ambient conditions is 118 cm3·g-1, the heat of adsorption is 30 kJ·mol-1, and it shows a high selectivity for C2H2/CO2 (3.5). These findings provide a new idea for the separation of C2H2/CO2 gas[31]. In addition, the researchers point out that the use of acetic acid as a solvent or pH control agent is an effective way to control the size of Ti-MOF crystals.
Solvothermal method is a typical method for the synthesis of Ti-MOF, and the optimization of reaction parameters (such as titanium source, solvent, temperature, etc.) in the experimental process is very important for its synthesis. Since then, researchers have prepared a variety of carboxylate ligand-based Ti-MOF by adjusting the solvent, pH, etc. It can be seen from Table 2 that the diversity of Ti-MOF ligands, from benzene ring to multi-ring, from single-head ligand to multi-head ligand, the new structure of Ti-MOF has been expanded rapidly.
表2 基于溶剂热法合成的Ti-MOF

Table 2 Ti-MOF synthesized by solvothermal synthesis

Ti-MOF Ti sources Organic linker Solvent environment ref
MTM-1 Ti(OiPr)4 Isonicotinic acid ACN 32
MIL-125 Ti(OiPr)4 Terephthalic acid DMF、Dry CH3OH 18
NH2-MIL-125 Ti(OiPr)4 2-Aminoterephthalic acid DMF、Dry CH3OH 21
MIP-207 Ti(OiPr)4 Trimesic acid Ac2O、CH3COOH 33
IEF Ti(OiPr)4 Squaric acid IPA、CH3COOH 34
NTU-9 Ti(OiPr)4 2,5-Dihydroxyterephthalic acid CH3COOH 17
MIL-167 Ti(OiPr)4 2,5-Dihydroxyterephthalic acid DEF、CH3OH 35
COK-69 Cp2TiCl2 Trans-1,4-cyclohexanedicarboxybic acid DMF、CH3COOH 36
Ti-MIL-101 TiCl3 Terephthalic acid DMF、C2H5OH 37,38
MIL-177 Ti(OiPr)4 3,3',5,5'-Tetracarboxydiphenylmethane CH3OH 39
ZSTU-1 Ti(OiPr)4 4,4',4″-Nitrilotribenzoic acid DryDMF 23
ZSTU-2 Ti(OiPr)4 1,3,5-Tris(4-Carboxyphenyl)benzene DryDMF 23
ZSTU-3 Ti(OiPr)4 4',4‴,4'''''-Nitrilotris([1,1'-biphenyl]-4-carboxylic acid) DryDMF 23
Ti-(Ti-TBP) TiCl4·2THF Tetra(4-carboxyphenyl)porphine DMF、CH3COOH 40
MUV-11 Ti(OiPr)4 Benzene-1,4-dihydroxamic acid DMF、CH3COOH 41
ACM-1 Ti(OiPr)4 4,4',4″,4‴-(1,9-dihydropyrene-1,3,6,8-tetrayl)tetrabenzoic acid DEF-C6H5Cl(1∶1)、
C2H5COOH		 42

NoteTi(OiPr)4: Titanium tetraisopropanolate; Cp2TiCl2: Titanocene dichloride;DMF: N,N-Dimethylformamide;DEF: N,N-Diethylformamide; THF: Tetrahydrofuran; ACN: Acetonitrile; CH3OH:Methanol; CH3COOH: Acetic acid; Ac2O: Acetic anhydride; IPA: Isopropyl alcohol; C2H5OH: Ethanol; C2H5COOH: Propionic acid; C6H5Cl: Chlorobenzene

Through the above research, we can find some synthesis rules of solvothermal synthesis of monometallic Ti-MOF: titanium alkoxides such as titanium isopropoxide are mostly used in metal Ti salts. Although titanium in titanium isopropoxide is tetravalent and four-coordinated, which is less than the six-coordinated number of titanium dioxide, titanium alkoxides are more stable due to the hydrophobicity and steric hindrance effect of alkoxy groups; Solvent environment is mostly inert operating environment, using organic solvents with very low water content, such as ultra-dry DMF, ultra-dry methanol, etc., and using acetic acid as pH control agent. This provides some guidance for subsequent researchers to explore the diversity of Ti-MOF.
The solvothermal method has the advantages of simple operation, various ligands to be selected, and rich structures to be synthesized. The disadvantage is that the high reactivity of titanium salts leads to too fast reaction rate, which makes the products easy to form microcrystals or powders, and reduces the possibility of obtaining crystals.

2.1.2 Solvothermal synthesis of bimetallic Ti/M-MOF

The strategy of solvothermal synthesis of Ti/M-MOF is similar to that of monometallic Ti-MOF, in which titanium precursor and organic ligand react in a closed system under solvothermal conditions. The difference is that the metal source of the reaction is not a single titanium salt, but two or three metal salts.
In 2013, Cui et al. Synthesized the first single-crystal Ti-MOF based on a carboxylate linker and a chiral salen linker unit[43]. The reaction process is shown in Figure 4. H2L (chiral salan ligand, prepared by Schiff base condensation of 3-tert-butyl-5- (4-pyridyl) salicylaldehyde and 1,2-diaminocyclohexane, and then reduced by sodium borohydride) is first connected with Ti(OBu)4 in DMF solution to generate Ti-based salan linkage unit.This structure is then connected with the 6-linked Cd-oxo cluster through pyridine bonds to form a two-dimensional framework, and then biphenyl-4,4 ′ -dicarboxylic acid (H2BPDC) acts as a pillar to connect these layers to each other to form a three-dimensional structure, which requires reaction at 80 ° C for 4 d[44]. The 6-linked Cd building blocks stack to form a 0.5 nm × 1.5 nm one-dimensional channel (Figure 5). This is a new topology, which the researchers named ctm topology.
图4 Cd-Ti-MOF-1的合成方法[13]

Fig. 4 Synthesis of Cd-Ti-MOF-1[13]

图5 (a) Cd-Ti-MOF-1的晶体结构; (b) ctm拓扑结构[13]

Fig. 5 (a) Crystal structure of Cd-Ti-MOF-1. (b) Topology of ctm[13]

Chun et al. First proposed Ti/M-MOF containing divalent metal ions and tetravalent metal ions in the secondary building unit (SBU), which can reduce the complexity of the preparation process of Ti-MOF. In 2013, researchers used the synthesis method of asymmetric difunctional ligands combined with Zn2+- and Ti4+-oxo clusters at the same time.Moreover, the synthesis process is simple, and orange crystals can be obtained by reacting the mixture of zinc nitrate (Ⅱ), titanium isopropoxide (Ⅳ) and 2-hydroxyterephthalic acid (H3obdc) in DMF solution at 90 ℃ for 24 H and at 120 ℃ for 55 H[45]. The crystal structure is constructed by coordination of metal ions with H3obdc to form Zn6Ti2 units, which extend to form a cubic network. The material has permanent porosity and stability and is named ZTOF-1. Zinc (Ⅱ) nitrate and titanium (Ⅳ) isopropoxide were reacted with 3-hydroxy-2,7-naphthalenedicarboxylic acid (H3ondc) and 1,4-diazacyclo [2.2.2] octane (dabco) under the same stepwise heating conditions using a similar method to obtain orange hexagonal columnar crystals, named ZTOF-2 (Fig. 6)[46]. From the synthesis process of ZTOF series materials, it can be seen that controlling the crystallization kinetics of crystals is an effective way to form large crystal Ti-MOF.
图6 ZTOF-1和ZTOF-2中的Zn/Ti-oxo簇[13]

Fig. 6 Zn/Ti-oxo clusters of ZTOF-1 and ZTOF-2[13]

When different metals form different building units, the distance between the building units can be adjusted to enhance the tunability of the structure. The Zn6Ti2 cluster in ZTOF-1 is composed of 12 obdc ligands, which are connected along six mutually perpendicular directions through π-π or CH-π interactions to form a bcu topology with a BET of 1045 m2·g-1. While in ZTOF-2, the first SBU is two tris Ti (Ⅳ) centers partially chelated by [Zn3(μ3-CO3)(OH2)3], showing a triangular prism geometry, the SBU of ZTOF-2 is a trinuclear unit [Zn3(CO2)6(dabco)], which is connected into a six-connected octahedron through dabco, and the BET is 1878 m2·g-1 (Fig. 7).
图7 ZTOF-1和ZTOF-2的代表性结构[13]

Fig. 7 Representative structures of ZTOF-1 and ZTOF-2[13]

Chun et al. Successfully synthesized O-centered trinuclear cluster and linear dicarboxylate linker organic frameworks CTOF-1 (hexagonal bipyramidal block crystal) and CTOF-2 (very small hexagonal plate crystal) with Co (II) and Ti (IV) metals and two ligands (terephthalic acid or 2-hydroxyterephthalic acid)[47]. Both MOFs are net-like structures (Fig. 8), and the cobalt-titanium-organic framework not only exhibits permanent porosity, but the existence of an irreversible phase transition between the two stable forms was also found by single crystal and powder X-ray diffraction studies.
图8 CTOF-1和CTOF-2的结构[47]

Fig. 8 Structures of CTOF-1 and CTOF-2[47]

Javier et al. Dissolved titanium (Ⅳ) isopropoxide, calcium chloride and trimesic acid in DMF, and heated at 120 ℃ for 48 H with acetic acid as pH regulator to form colorless octahedral crystal MUV-10 (Ca)[24]. The material is a three-dimensional porous solid formed by interconnecting fully deprotonated trimesic anions and tetranuclear Ti2Ca2(μ3-O)2(H2O)4(CO2)8 clusters. MUV-10 (Ca) consists of octahedral Ti (Ⅳ) and six-coordinated Ca (Ⅱ) centers with trigonal prismatic geometry (Fig. 9). Although the introduction of divalent metals into SBU can become a weak point for hydrolysis and impair the stability of the material, MUV-10 (Ca) maintains its structural integrity between pH 2 and 12 (fig. 10).
图9 MUV-10(Ca)的配位结构[24]

Fig. 9 The structure of MUV-10(Ca)[24]

图10 MUV-10(Ca)在pH=2~12的稳定性[24]

Fig. 10 Stability of MUV-10(Ca) between pH 2 and 12[24]

Sergio et al. Used another relatively inert titanium source, TiBALD (titanium diammonium bis (2-hydroxypropionate) dihydroxide), and 5,10,15,20-tetrakis (3-hydroxyphenyl) porphyrin ligand to generate microporous bimetallic MOF MIL-173 (Ti/Zr) in DMF and hydrochloric acid solution by one-step method, and MIL-173 (Ti/Zr) with different Ti contents could be synthesized by changing the Ti/Zr ratio in the reaction solution[48]. However, when the Ti content increases, the crystallinity and porosity of the material decrease rapidly (as shown by scanning electron microscopy (SEM) in Fig. 11). The material can decompose H2O into H2 and O2 under simulated sunlight irradiation without any catalyst, showing excellent photocatalytic activity, which provides an effective idea for the development of efficient MOF-based materials as photocatalysts for solar-driven water splitting.
图11 不同Ti含量的MIL-173(Zr/Ti)的SEM[48]

Fig. 11 SEM images of MIL-173(Ti/Zr) samples of variable Ti content[48]

Organic titanium sources, such as titanium isopropoxide, Ti(OBu)4, TiBALD, etc., are mostly used in the direct synthesis of bimetallic Ti-MOF by hydrothermal method, because organic titanium sources are more stable than inorganic titanium sources, and the existence of low-valent metals in the reaction process can properly reduce the reactivity of Ti salts. The solvent environment is also more inclined to organic solvents, such as DMF.
The advantage of this method is that Ti/M-MOF has bimetallic characteristics compared with the original monometallic, so it shows more obvious advantages in gas storage/separation and heterogeneous catalysis[49]. The disadvantage of this method is that the synthesis of bimetallic MOF relies on the use of metal ions with similar charge and ionic radius, but the high polarization ability of Ti4+ hinders the direct reaction of other metals with ligands.This may lead to poor control of their distribution in the final material, resulting in the formation of segregated phases, so the bimetallic synthesis strategy depends on the control of the solvent environment and the selection of appropriate ligands[50].

2.2 Post-exchange synthesis of Ti-MOF

2.2.1 Preparation of Ti/M-MOF by Post-exchange of M-MOF

Aiming at the highly challenging problem of direct synthesis of Ti-MOF by solvothermal method, researchers creatively proposed the post-exchange synthesis method to prepare a series of Ti/M bimetallic MOF[51⇓~53]. This method first needs to prepare MOF materials with other central metals, and then replace part of the central metals on the framework with titanium atoms by ion exchange to obtain Ti/M-MOF.
Cohen and Wang et al. First proposed the concept of post-synthetic modification (PSM) in MOF materials and anchored the amide functional group into the framework of IR-MOF-3 through a condensation reaction[54]. PSM technology can be used to synthesize MOF containing functionalized functional groups, which may be difficult to coordinate with metals and cannot be obtained by direct synthesis. In addition, many new materials can also be obtained by metal ion exchange through PSM, and the researchers prepared Ti/M-MOF by immersing the original MOF in a solution containing titanium salts, such as TiCl3 or TiCX4(X=Br or Cl)[13].
Kim et al. reported a Zr/Ti bimetallic MOF UiO-66 (Zr/Ti), which increased the exchange rate of Ti atoms from 53% to 94% by PSM. In 2018, Cohen et al. used TEM to prove that the synthesized MOF was not a bimetallic MOF, but a MOF @ metal oxide (Fig. 12)[55][56]. MOF-5 (Zn/Ti) can also be obtained by partial exchange of Ti (Ⅲ) and Zn (Ⅱ), but the exchange rate of Ti (Ⅲ) is relatively low, only 2%[57]. This synthesis scheme provides a new idea for the preparation of Ti-MOF by post-exchange strategy (Fig. 13).
图12 PSM法制备UiO-66@TiO2的机理示意图[56]

Fig. 12 The mechanism of UiO-66@TiO2 by PSM[56]

图13 PSM策略制备的MOF-5(Zn/Me)(其中Me=Ti、V、Cr、Mn、Fe)[57]

Fig. 13 Synthesis of MOF-5(Zn/Me) (Me=Ti, V, Cr, Mn, Fe)[57]

In 2016, Zhou et al. Proposed a general Ti-MOF synthesis route, which used high-valence metathesis and oxidation (HVMO) method to synthesize a series of porous photoactive titanium MOFs, PCN-333 (Sc) -Ti, MIL-100 (Sc) -Ti, MOF-74 (Zn) -Ti and MOF-74 (Mg) -Ti (Fig. 14). Ti3+ ion exchange was used to obtain the intermediate Ti (Ⅲ) -MOF analog, followed by mild oxidation in air to produce Ti (IV) -MOF. The exchange ratios of Ti atoms in PCN-333 (Sc/Ti), MIL-100 (Sc/Ti), MOF-74 (Zn/Ti) and MOF-74 (Mg/Ti) were 88.8%, 48.8%, 94.7% and 37.9%, respectively, as evidenced by inductively coupled plasma mass spectrometry (ICP-MS). Obviously, the successful synthesis of various Ti-MOFs from low-cost MOFs by HVMO method not only introduces an effective method for the synthesis of Ti-MOF, but also opens up new ideas for the exploration of Ti-MOF materials.
图14 HVMO方法制备的Ti-MOF [20]

Fig. 14 Synthesis of Ti-MOF by HVMO[20]

The titanium source used in the post-exchange synthesis is active titanium source TiCl3 and TiCl4, the solvent environment is mostly organic solvent, and the operation process is almost all in the glove box. Post-exchange synthesis provides a route to synthesize new Ti-MOFs with known structures, which can not only functionally introduce Ti ions into the original MOF, but also indirectly synthesize materials that cannot be synthesized by direct synthesis. However, this method has the disadvantage that only titanium tetrachloride or titanium trichloride with Ti ions can be selected, but the coordination number of titanium tetrachloride and titanium trichloride is less than that of TiO2, which is very easy to hydrolyze in water to form more stable titanium dioxide and release hydrochloric acid, and the operation process is dangerous. Moreover, in order to prevent the hydrolysis of the active titanium source, the whole operation process can only be carried out in a glove box, which undoubtedly brings some difficulties to the synthesis process, and this method is easy to form MOF @ metal oxide rather than Ti/M-MOF. Therefore, even though this is a very good strategy for the synthesis of Ti-MOF, it has not been widely used because of the complexity of its operation.

2.2.2 Preparation of Ti/M2-MOF by Post-exchange of Ti/M1-MOF

In the post-exchange synthesis method, not only the diversity of Ti/M-MOF can be expanded on the basis of monometallic MOF, but also the Ti/M2-MOF can be prepared by post-exchange of M1 metal on the basis of bimetallic Ti/M1-MOF. On the basis of MUV-10 (Ca), Natalia et al. Reported a new synthesis method, which is based on the discovery that bimetallic MUV-10 crystals are composed of soft and hard metals, and can exchange metals at soft metal sites while maintaining their structural integrity[50]. A series of mesoporous or microporous bimetallic MOFs were synthesized by metal exchange with transition metals (Fe, Co, Ni, Cu, Zn) in methanol at 65 ℃. In contrast to direct synthesis, this metal-induced topological transformation is a dynamic phenomenon that can be controlled over time until the complete transformation of the material (Figure 15). This method enables the formation of bimetallic Ti-MOF that is not available under high temperature solvothermal conditions, which provides a new idea for the synthesis of bimetallic Ti-MOF.
图15 金属交换策略制备的双金属Ti-MOF[50]

Fig. 15 Heterometallic Ti-MOFs by Metal-exchange reactions[50]

2.3 Construction method of in situ SBUs

Due to the strong Ti — O bond, the reversible bond polymerization/dissociation process in the synthesis of Ti-MOF is very difficult, which is a challenge for the realization of crystalline Ti-MOF. The construction method of in situ generation of SBUs is another effective method to control the hydrolytic condensation reaction of Ti[58]. The method comprises the following steps of: firstly, forming a titanium-oxygen cluster from a metal oxygen nucleus and an organic ligand, wherein the titanium-oxygen cluster is a polynuclear titanium complex, and is generally more stable to water than a titanium alkoxide, because the titanium-oxide cluster has a higher coordination number and has a ligand which is more difficult to hydrolyze than the alkoxide, such as a carboxylate[59]. After that, the terminal ligand of the titanium-oxygen cluster is connected with another organic ligand to build the Ti-MOF framework.
Yuan et al. Reported a Ti-MOF in 2015, which first mixed titanium source (titanium isopropoxide), organic ligand (4-aminobenzoic acid) and isopropanol solution under solvothermal conditions to generate 6-linked titanium oxo cluster Ti6O6(OiPr)6(abz)6(abz=4- aminobenzoate) at 100 ° C[19]; The titanium oxo cluster reacted with TCPP ( (4-carboxyphenyl) porphyrin) in N, N-diethylformamide (DEF) solution in the presence of benzoic acid at 150 ℃ for 48 H to form a porphyrin-based Ti-MOF, PCN-22 (Fig. 16), which exhibited a large specific surface area (1284 m2·g-1). Interestingly, after the formation of the MOF, the titanium oxo clusters were found to rearrange, resulting in an unprecedented 7-linked Ti7O6 C luster (Figure 17).
图16 PCN-22合成过程[19]

Fig. 16 Synthesis process of PCN-22[19]

图17 PCN-22的7-连接钛簇[13]

Fig. 17 7-connected Ti-oxo-clusters of PCN-22[13]

In the above reaction, the rearrangement from the 6-linked titanium cluster to the 7-linked titanium cluster may hinder the determination of the crystal structure, so this process does not achieve the synthesis of the target structure. In order to solve this problem, Yaghi et al.However, the cluster was formed by the reaction of titanium isopropoxide with 4-aminobenzoic acid in methanol at 120 ° C, and the terminal —NH2 group of the cluster was linked together with the carbonyl group of benzene-1,4-dialdehyde through imine condensation to obtain MOF-901 with an isonetwork structure, which is the first MOF obtained by combining the preparation strategy of MOF and covalent organic framework (COF)[22]. In addition, an isostructural MOF of larger pore size — MOF-902 — can be obtained by using elongated aldehyde ligands[60]. This was the only successful case of two isostructural Ti-MOFs composed of ligands of different lengths at that time (Figure 18).
图18 等网状的MOF-901和MOF-902[60]

Fig. 18 Isoreticular MOF-901 and MOF-902[60]

The titanium source for the construction method of in situ generation of SBUs is the polynuclear titanium complex, and their general formula is TinOm(OR/Cl)x(L)y. This kind of titanium cluster combines the metal core and organic ligands (L is alkoxide, β-diketonate, carboxylate, and phenolate), so it is very rich in size, geometry, degree of O/Ti condensation, coordination number of titanium cation, and organic complexing ligands (Fig. 19)[59][61⇓⇓~64]. Compared with titanium alkoxides, these oxotitanium clusters possess higher coordination numbers and less hydrolyzable ligands, such as oxotitanium cluster ——Ti6O6(OiPr)6(abz)6.
图19 Ti-oxo-clusters的多样性[61⇓~63]

Fig. 19 Diversity of Ti-oxo-clusters[61⇓~63]

The construction method of in situ generation of SBUs is considered to be an effective method to control the hydrolysis-condensation reaction of Ti source, and the Ti-oxo-cluster provides guidance for the synthesis of single crystal DGIST-1 (different in size and shape from PCN-22), Ti3-BPBC, MIP-208 and other Ti-MOFs (Table 3), which proves that this strategy is an effective method to expand the diversity of Ti-MOFs. However, clustering before synthesis adds reaction steps and faces new problems: if the cluster is not stable enough, it is difficult to dry it out of the mother liquor; If the cluster is too stable, it is difficult to coordinate with a new ligand to form a new MOF. Based on this, many researchers still hope to design or synthesize titanium oxide clusters with moderate stability, and then form Ti-MOF single crystals through solvothermal reaction.
表3 基于原位生成SBUs构筑法的Ti-MOF

Table 3 Ti-MOF synthesized by in situ SBUs construction methods

Ti-MOF Ti sources Organic linker Solvent environment ref
PCN-22
Ti6O6(OiPr)6(abz)6		 Ti(iPrO)4 4-Aminobenzoic acid IPA 19
PCN-22 Ti6O6(OiPr)6(abz)6 Tetrakis(4-carboxyphenyl)porphyrin DEF、C6H5COOH、
DGIST-1
(Ti6O6(OiPr)6(t-BA)6)		 Ti(iPrO)4 4-Aminobenzoic acid IPA 65
DGIST-1 Ti6O6(OiPr)6(t-BA)6 Tetrakis(4-carboxyphenyl)porphyrin DEF、C6H5COOH
MIP-208
Ti8AF cluster		 Ti(iPrO)4 Ac2O CH3COOH 66
MIP-208 Ti8AF cluster 5-Aminoisophthalic acid Ac2O、C2H5COOH、CH3OH
Ti3-BPBC
(Ti6O6(OiPr)6(abz)6)		 Ti(iPrO)4 4-Aminobenzoic acid IPA 67
Ti3-BPBC Ti6O6(OiPr)6(abz)6 Biphenyl-4,4'-dicarboxylic acid DMF、C2H5COOH
MIL-100(Ti)
Ti6O6(4-tbbz)6(OiPr)6		 Ti(iPrO)4 4-tert-butylbenzoic acid IPA-THF (3∶1) 68
MIL-100(Ti) Ti6 Trimesic acid ACN-THF(3∶1)

NoteTi(OiPr)4: Titanium tetraisopropanolate;DMF: N,N-Dimethylformamide;DEF: N,N-Diethylformamide; THF: Tetrahydrofuran; ACN: Acetonitrile; CH3OH: Methanol; CH3COOH: Acetic acid; C2H5OH: Ethanol; C2H5COOH: Propionic acid; IPA: Isopropyl alcohol; Ac2O: Acetic anhydride; C6H5COOH: Benzoic acid

3 Conclusion and prospect

Although the synthesis of Ti-MOF faces great challenges, which limits its diversity and application, due to its high stability and photoresponse characteristics, researchers are still developing the design of Ti-MOF structures and exploring new strategies. In this paper, the research progress in the synthesis of Ti-MOF in recent years is introduced, and the advantages and disadvantages of solvothermal direct synthesis, post-exchange synthesis and in situ formation of SBUs construction are summarized. The main control methods in the synthesis are summarized as follows: (1) controlling the metal source to reduce the reactivity of the precursor; (2) Control of synthesis conditions and crystallization kinetics to provide a suitable coordination environment (Table 4). Based on this, the author puts forward two prospects for expanding the diversity of Ti-MOF in the future: one is to use Ti-oxo-clusters to prepare Ti-MOF: the titanium-oxygen clusters based on alcohol or carboxylic acid ligands are easy to deteriorate in the air, and the titanium-oxygen clusters based on catechol and acid ligands are too stable to coordinate.Titanium oxide clusters with moderate stability were screened or designed and synthesized, and Ti-MOF was reasonably constructed by controlling the reaction conditions. The other is to expand the diversity of bimetallic Ti/M-MOF. Bimetallic Ti/M-MOF not only retains the stability of Ti-MOF, but also endows other metals with advantages, which is a promising synthesis strategy.
表4 三种合成方法的对比

Table 4 Comparison of three synthesis methods

Method Advantage and disadvantage Common synthesis condition
Solvothermal synthesis Ti-MOF Ad: The available ligands are diverse, and the synthesized structures are rich with few restrictions.
Dis: High reaction activity, easy hydrolysis, and the majority of synthesized sample powders.		 Ti sources: organic Ti sources
Solvent environment: organic solvent
pH controller:acetic acid
Heterometallic Ti/M-MOF Ad: Properly reduce the reactivity of Ti and synthesize materials with heterometallic advantages.
Dis: The high polarizing power of Ti4+ prevents a direct reaction with other metals that would likely result in poor control over their distribution in the final material for the formation of segregated phases.		 Ti sources:organic sources
Solvent environment:organic solvent
Post-synthetic modification M-MOF transform into Ti/M-MOF
by PSM		 Ad: Capable of functionalizing the introduction of specific Ti ions into existing MOFs.
Dis: 1. Titanium sources are prone to severe hydrolysis and are dangerous to operate.
2. Easy to be MOF@metal oxide rather than Ti/M-MOF		 Ti sources:TiCl3、TiCl4 etc.
Synthetic environment:Inert
gas environment
Ti/M1-MOF transform into Ti/M2-MOF by PSM Ad: Heterometallic Ti-MOF that cannot be obtained under high-temperature solvothermal conditions can be synthesized.
Dis: Ti/M1-MOF is relatively rare, and not all bimetallic MOFs are suitable for this strategy.
In situ SBUs construction methods Ad: It is another effective method to control the hydrolysis Condensation reaction reaction of Ti.
Dis: The addition of reaction steps has made the stability of titanium clusters another factor limiting the reaction.		 Ti sources:Ti6O6(OiPr)6(abz)6
Solvent environment:organic solvent

References

Publishing order | Descend order by publishing year | Descend order by cited within
[1]
Eddaoudi M, MolerD B, Li H L, Chen B L, Reineke T M, O’Keeffe M, Yaghi O M. Acc. Chem. Res., 2001, 34(4): 319.

[2]
TranchemontagneD J, Mendoza-Cortés J L, O’Keeffe M, Yaghi O M. Chem. Soc. Rev., 2009, 38(5): 1257.

[3]
Wang H, Yuan X Z, Wu Y, Zeng G M, Chen X H, Leng L J, Li H. Appl. Catal. B Environ., 2015, 174/175: 445.

[4]
Wang H, Yuan X Z, Wu Y, Chen X H, Leng L J, Zeng G M. RSC Adv., 2015, 5(41): 32531.

[5]
Schaate A, Roy P, Godt A, Lippke J, Waltz F, Wiebcke M, Behrens P. Chem. A Eur. J., 2011, 17(24): 6643.

[6]
Mouchaham G, Cooper L, Guillou N, Martineau C, Elkaïm E, Bourrelly S, Llewellyn P L, Allain C, Clavier G, Serre C, Devic T. Angew. Chem. Int. Ed., 2015, 54(45): 13297.

[7]
Yuan S, Qin J S, Lollar C T, Zhou H C. ACS Cent. Sci., 2018, 4(4): 440.

[8]
Canivet J, Fateeva A, Guo Y M, Coasne B, Farrusseng D. Chem. Soc. Rev., 2014, 43(16): 5594.

[9]
Wang C H, Liu X L, KeserDemir N, Chen J P, Li K. Chem. Soc. Rev., 2016, 45(18): 5107.

[10]
Burtch N C, Jasuja H, Walton K S. Chem. Rev., 2014, 114(20): 10575.

[11]
Nguyen H L. J. Phys. Energy, 2021, 3(2): 021003.

[12]
Cavka J H, Jakobsen S, Olsbye U, Guillou N, Lamberti C, Bordiga S, Lillerud K P. J. Am. Chem. Soc., 2008, 130(42): 13850.

[13]
Nguyen H L. New J. Chem., 2017, 41(23): 14030.

[14]
Nasalevich M A, van der Veen M, Kapteijn F, Gascon J. CrystEngComm, 2014, 16(23): 4919.

[15]
Abedi S, Morsali A. New J. Chem., 2015, 39(2): 931.

[16]
Guillerm V, Gross S, Serre C, Devic T, Bauer M, Férey G. Chem. Commun., 2010, 46(5): 767.

[17]
Gao J K, Miao J W, Li P Z, Teng W Y, Yang L, Zhao Y L, Liu B, Zhang Q C. Chem. Commun., 2014, 50(29): 3786.

[18]
Dan-Hardi M, Serre C, Frot T, Rozes L, Maurin G, Sanchez C, Férey G. J. Am. Chem. Soc., 2009, 131(31): 10857.

[19]
Yuan S, Liu T F, FengD W, Tian J, Wang K C, Qin J S, Zhang Q, Chen Y P, Bosch M, Zou L F, Teat S J, Dalgarno S J, Zhou H C. Chem. Sci., 2015, 6(7): 3926.

[20]
Zou L F, FengD W, Liu T F, Chen Y P, Yuan S, Wang K C, Wang X, Fordham S, Zhou H C. Chem. Sci., 2016, 7(2): 1063.

[21]
Hendon C H, TianaD, Fontecave M, Sanchez C, D’arras L, Sassoye C, Rozes L, Mellot-Draznieks C, Walsh A. J. Am. Chem. Soc., 2013, 135(30): 10942.

[22]
Nguyen H L, Gándara F, Furukawa H, Doan T L H, Cordova K E, Yaghi O M. J. Am. Chem. Soc., 2016, 138(13): 4330.

[23]
Li C Q, Xu H, Gao J K, Du W N, Shangguan L Q, Zhang X, Lin R B, Wu H, Zhou W, Liu X F, Yao J M, Chen B L. J. Mater. Chem. A, 2019, 7(19): 11928.

[24]
Castells-Gil J, Padial N M, Almora-Barrios N, Albero J, Ruiz-Salvador A R, González-Platas J, García H, Martí-Gastaldo C. Angew. Chem. Int. Ed., 2018, 57(28): 8453.

[25]
Castells-Gil J, Padial N M, Almora-Barrios N, Gil-San-Millán R, Romero-Ángel M, Torres V, da Silva I, Vieira B C J, Waerenborgh J C, Jagiello J, Navarro J A R, Tatay S, Martí-Gastaldo C. Chem., 2020, 6(11): 3118.

[26]
Sun Y Y, LuD F, Sun Y X, Gao M Y, Zheng N, Gu C, Wang F, Zhang J. ACS Mater. Lett., 2021, 3(1): 64.

[27]
Li H L, Eddaoudi M, O’Keeffe M, Yaghi O M. Nature, 1999, 402(6759): 276.

[28]
Serre C, Férey G. Inorg. Chem., 1999, 38(23): 5370.

[29]
Serre C, Groves J A, Lightfoot P, Slawin A M Z, Wright P A, Stock N, Bein T, Haouas M, Taulelle F, Férey G. Chem. Mater., 2006, 18(6): 1451.

[30]
Khaletskaya K, Pougin A, Medishetty R, Rösler C, Wiktor C, Strunk J, Fischer R A. Chem. Mater., 2015, 27(21): 7248.

[31]
Cai Y L, Zou L J, Ji Q H, Yong J Y, Qian X F, Gao J K. Polyhedron, 2020, 190: 114771.

[32]
Wang C, Liu C, He X, Sun Z M. Chem. Commun., 2017, 53(85): 11670.

[33]
Wang S J, Reinsch H, Heymans N, Wahiduzzaman M, Martineau-Corcos C, De Weireld G, Maurin G, Serre C. Matter, 2020, 2(2): 440.

[34]
Salcedo-Abraira P, Babaryk A A, Montero-Lanzuela E, Contreras-Almengor O R, Cabrero-Antonino M, Grape E S, Willhammar T, Navalón S, Elkäim E, García H, Horcajada P. Adv. Mater., 2021, 33(52): 2106627.

[35]
Assi H, Pardo Pérez L C, Mouchaham G, Ragon F, Nasalevich M, Guillou N, Martineau C, Chevreau H, Kapteijn F, Gascon J, Fertey P, Elkaim E, Serre C, Devic T. Inorg. Chem., 2016, 55(15): 7192.

[36]
Bueken B, Vermoortele F, VanpouckeD E P, Reinsch H, Tsou C C, Valvekens P, De Baerdemaeker T, Ameloot R, Kirschhock C E A, Van Speybroeck V, Mayer J M, De VosD. Angew. Chem. Int. Ed., 2015, 54(47): 13912.

[37]
Mason J A, Darago L E, Lukens W W Jr, Long J R. Inorg. Chem., 2015, 54(20): 10096.

[38]
Li Y F, Aschauer U, Chen J, Selloni A. Acc. Chem. Res., 2014, 47(11): 3361.

[39]
Wang S J, Kitao T, Guillou N, Wahiduzzaman M, Martineau-Corcos C, Nouar F, Tissot A, Binet L, Ramsahye N, Devautour-Vinot S, Kitagawa S, Seki S, Tsutsui Y, Briois V, Steunou N, Maurin G, Uemura T, Serre C. Nat. Commun., 2018, 9: 1660.

[40]
Lan G X, Ni K Y, Veroneau S S, Feng X Y, Nash G T, Luo T K, Xu Z W, Lin W B. J. Am. Chem. Soc., 2019, 141(10): 4204.

[41]
Padial N M, Castells-Gil J, Almora-Barrios N, Romero-Angel M, da Silva I, Barawi M, García-Sánchez A, de la Peña O’Shea V A, Martí-Gastaldo C. J. Am. Chem. Soc., 2019, 141(33): 13124.

[42]
Cadiau A, Kolobov N, Srinivasan S, Goesten M G, Haspel H, Bavykina A V, Tchalala M R, Maity P, Goryachev A, Poryvaev A S, Eddaoudi M, Fedin M V, Mohammed O F, Gascon J. Angew. Chem. Int. Ed., 2020, 59(32): 13468.

[43]
Zhu C F, Chen X, Yang Z W, Du X, Liu Y, Cui Y. Chem. Commun., 2013, 49(64): 7120.

[44]
Xuan W M, Ye C C, Zhang M N, Chen Z J, Cui Y. Chem. Sci., 2013, 4(8): 3154.

[45]
Hong K, Bak W, Chun H. Inorg. Chem., 2013, 52(10): 5645.

[46]
Hong K, Chun H. Chem. Commun., 2013, 49(93): 10953.

[47]
Hong K, Bak W, MoonD, Chun H. Cryst. GrowthDes., 2013, 13(9): 4066.

[48]
Gikonyo B, Montero-Lanzuela E, Baldovi H G, De S, Journet C, Devic T, Guillou N, TianaD, Navalon S, Fateeva A. J. Mater. Chem. A, 2022, 10(46): 24938.

[49]
Li M M, Yuan J W, Wang G, Yang L J, Shao J X, Li H, Lu J M. Sep. Purif. Technol., 2022, 298: 121658.

[50]
Padial N M, Lerma-Berlanga B, Almora-Barrios N, Castells-Gil J, da Silva I, de la Mata M, Molina S I, Hernández-Saz J, Platero-Prats A E, Tatay S, Martí-Gastaldo C. J. Am. Chem. Soc., 2020, 142(14): 6638.

[51]
Shultz A M, Sarjeant A A, Farha O K, Hupp J T, Nguyen S T. J. Am. Chem. Soc., 2011, 133(34): 13252.

[52]
Grancha T, Ferrando-Soria J, Zhou H C, Gascon J, Seoane B, Pasán J, Fabelo O, Julve M, Pardo E. Angew. Chem. Int. Ed., 2015, 54(22): 6521.

[53]
Li B J, Gui B, Hu G P, YuanD Q, Wang C. Inorg. Chem., 2015, 54(11): 5139.

[54]
Wang Z Q, Cohen S M. J. Am. Chem. Soc., 2007, 129(41): 12368.

[55]
Kim M, Cahill J F, Fei H H, Prather K A, Cohen S M. J. Am. Chem. Soc., 2012, 134(43): 18082.

[56]
Denny M S Jr, Parent L R, Patterson J P, Meena S K, Pham H, Abellan P, Ramasse Q M, Paesani F, Gianneschi N C, Cohen S M. J. Am. Chem. Soc., 2018, 140(4): 1348.

[57]
Brozek C K, Dincă M. J. Am. Chem. Soc., 2013, 135(34): 12886.

[58]
Yaghi O M, O’Keeffe M, Ockwig N W, Chae H K, Eddaoudi M, Kim J. Nature, 2003, 423(6941): 705.

[59]
Assi H, Mouchaham G, Steunou N, Devic T, Serre C. Chem. Soc. Rev., 2017, 46(11): 3431.

[60]
Nguyen H L, Vu T T, LeD, Doan T L H, Nguyen V Q, Phan N T S. ACS Catal., 2017, 7(1): 338.

[61]
Gao M Y, Wang Z R, Li Q H, LiD J, Sun Y Y, Andaloussi Y H, Ma C, Deng C H, Zhang J, Zhang L. J. Am. Chem. Soc., 2022, 144(18): 8153.

[62]
Lv H T, Li H M, Zou GD, Cui Y, Huang Y, Fan Y. Dalton Trans., 2018, 47(24): 8158.

[63]
Hong K, Bak W, Chun H. Inorg. Chem., 2014, 53(14): 7288.

[64]
Hong K, Chun H. Inorg. Chem., 2013, 52(17): 9705.

[65]
Keum Y, Park S, Chen Y P, Park J. Angew. Chem. Int. Ed., 2018, 57(45): 14852.

[66]
Wang S J, Cabrero-Antonino M, Navalón S, Cao C C, Tissot A, Dovgaliuk I, Marrot J, Martineau-Corcos C, Yu L, Wang H, Shepard W, García H, Serre C. Chem, 2020, 6(12): 3409.

[67]
Feng X Y, Song Y, Chen J S, Li Z, Chen E Y, Kaufmann M, Wang C, Lin W B. Chem. Sci., 2019, 10(7): 2193.

[68]
Castells-Gil J, Padial N M, Almora-Barrios N, da Silva I, MateoD, Albero J, García H, Martí-Gastaldo C. Chem. Sci., 2019, 10(15): 4313.

Options
Outlines

/

〈 〉