Abstract: A series of novel isostructural three-dimensional rare-earth metal-organic frameworks (MOFs), [RE(BTDI)3(H2O)4]·4H2O·solv (RE-BTDI, RE = Er, Dy, Y) were synthesized by solvothermal method using tetracarboxylic acid ligand containing thiadiazole groups, 5,5'-(benzothiadiazole-4,7-diyl)diisophthalic acid (H4BTDI) and rare earth metal nitrates. The rare earth metal nodes on the frameworks of RE-BTDI are Lewis acidic sites which was confirmed qualitatively and quantitatively by Py-IR and NH3-TPD. Meanwhile, the thiadiazole groups introduced by ligands can be used as polar sites to enhance the CO2 adsorption performance of these materials. Under the synergy of the Lewis acidic sites and thiadiazole groups, RE-BTDI show good catalytic activity for the cycloaddition reaction of CO2 and a series of epoxides. Under the condition of 80 ℃, 1MPa CO2, 0.1 mol% RE-BTDI catalyzed the cycloaddition reaction of CO2 and styrene oxide for 5 hours, the yield of styrene cyclic carbonate can reach 90%, and after 5 rounds of cyclic catalysis, the catalytic activity and catalyst structure are maintained well. In addition, for other epoxides, the yields of the corresponding cyclic carbonate products can reach 92.5% to 99% catalyzed by RE-BTDI under relatively mild conditions.

Key words: Metal Organic Frameworks, Rare-earth, Thiadiazole, Heterogeneous catalysis, CO₂ cycloaddition