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

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)center dot 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 center dot 624 center dot 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.