A High-Performance Zinc-Organic Framework with Accessible Open Metal Sites Catalyzes CO2 and Styrene Oxide into Styrene Carbonate under Mild Conditions

A new tetratopic bridging ligand 1,1'-(propane-1,3diyl)bis(1H-pyrazole-3,5-dicarboxylic acid) (PDC) with functional pyrazole groups was designed and used for reacting with environmentally friendly zinc centers in mixed solvents; the resulting framework [Zn3.5(PDC)2( H2O)10] (abbreviated as MOF Zn-2PDC) contained numerous organic-inorganic crablike blocks and had high density of zinc sites and coordinated water molecules. Abundant open metal sites (OMSs) were generated after the removal of coordinated water molecules by vacuum drying, which produced exceptionally catalytic performance for CO2 cycloaddition to bulky styrene oxide, and the produced styrene carbonate yield and selectivity reached up to 86 and 97% under mild conditions of 55 degrees C, 12 h, and 1 MPa. Moreover, MOF Zn- 2PDC also showed general applicability to other bulky epoxides. Meanwhile, the MOF Zn-2PDC catalyst remained with good catalytic performance after six cycles.