Copper-Cluster-Based MOF as a Heterogeneous Catalyst for CO₂ Chemical Fixation and Azide–Alkyne Cycloaddition

Abstract

Developing metal–organic frameworks (MOFs) as heterogeneous catalysts attracts much attention because their high internal surface areas and open metal sites may facilely improve the catalytic activity. In this study, a copper-cluster-based MOF, denoted as {2Cu(L)(A)·3H2O} n (1, L = bis(4-(4H-1,2,4-triazol-4-yl)phenyl)methane, A = deprotonated 1,4-naphthalenedicarboxylic acid), has been constructed. 1 has a (3,10)-connected three-dimensional (3D) porous network structure with a new topology of {48·624·83}{43}2. Structural analysis reveals that copper ions adopt two coordination modes in the secondary building unit, forming polyhedral copper clusters by Cu–O–Cu bridge bonds. Detailed studies show that 1 can be employed as an efficient heterogeneous catalyst for converting CO2 to cyclic carbonates in 81.0–99.0% yield under 1 atm CO2 and solvent-free conditions. Furthermore, 1 retains good catalytic efficiency after 10 cycles (83.0% conversion). Moreover, 1 exhibits good catalytic performance toward azide–alkyne cycloaddition (AAC) reactions in an aqueous solution with the addition of sodium ascorbate, yielding a series of 1,4-disubstituted 1,2,3-triazoles in high yields (over 99.0%) and presenting recyclable ability.

Organotitanium Click Chemistry

“…These organotitanium chlorides may serve as building blocks for attaining new organotitanium azides, simply undergoing the same strategic pathway outlined in Scheme 6. The list of organotitanium complexes in Figure 2 contains a monocloride (23), several dichlorides (21,22,25,26,28,29,30,31) and trichlorides (20,24,27). In the following discussion, all click chemical transformations applicable to dichlorides will be represented by the framework of complex 17, and click transformations of trichlorides by the framework of complex 20.…”

Organotitanium Click Chemistry

“…These organotitanium chlorides may serve as building blocks for attaining new organotitanium azides, simply undergoing the same strategic pathway outlined in Scheme 6. The list of organotitanium complexes in Figure 2 contains a monocloride (23), several dichlorides (21,22,25,26,28,29,30,31) and trichlorides (20,24,27). In the following discussion, all click chemical transformations applicable to dichlorides will be represented by the framework of complex 17, and click transformations of trichlorides by the framework of complex 20.…”

Thermally activated bipyridyl-based Mn-MOFs with Lewis acid–base bifunctional sites for highly efficient catalytic cycloaddition of CO2 with epoxides and Knoevenagel condensation reactions

“…25–34 In particular, MOFs have inherent advantages in catalysis because they possess multiple active sites including Lewis/Brønsted acid sites and Lewis base sites, which can make the use of MOFs feasible for the catalytic process. 23,35–37 Moreover, the heterogeneous nature of MOFs increases the possibility of MOF catalysts for recycling and recovery. 35–37 However, the key limitation of MOF catalysts is a lack of thermal and chemical stability, which makes it difficult to maintain their high porosities and active sites during the catalytic process.…”

“…23,35–37 Moreover, the heterogeneous nature of MOFs increases the possibility of MOF catalysts for recycling and recovery. 35–37 However, the key limitation of MOF catalysts is a lack of thermal and chemical stability, which makes it difficult to maintain their high porosities and active sites during the catalytic process. To overcome this limitation, it is urgent to develop stable MOFs for heterogeneous catalysis.…”