The multifunctional design of metal-organic framework by applying linker desymmetrization strategy: synergistic catalysis for high CO2-epoxide conversion

Herein, a novel copper metal-organic framework (MOF), [Cu-2(CPTPTA)(H2O)]center dot CH3NH3+center dot 4H(2)O center dot 7NMF (1) (H(5)CPTPTA = 5 '-(4-carboxyphenyl)-[1,1 ':3 ',1 ''-terphenyl]-3,3 '',5,5 ''-tetracarboxylic acid, NMF = N-methylformamide), has been successfully synthesized via solvothermal reaction. By applying a linker desymmetrization strategy, compound 1 was constructed by a reduced-symmetry ligand CPTPTA(5-), leading to three types of channels with various functional sites. Meanwhile, the functional sites promoted the adsorption of CO2, the uptakes being 123.2(2) and 66.8(2) cm(3) g(-1) at 273 and 298 K, respectively. Furthermore, the smaller channel exists as two kinds of active sites: Lewis acid sites (LASs) and Bronsted acid sites (BASs); whereas the larger one only exists as LASs. The synergistic catalysis of LASs and BASs makes compound 1 exhibit excellent CO2 cycloaddition efficiency towards propylene oxide, and the yield can reach 97%. Overall, such a linker desymmetrization strategy can afford an effective approach to synthesize novel functional MOF materials.