The design of a novel and resistant Zn(PZDC)(ATZ) MOF catalyst for the chemical fixation of CO2 under solvent-free conditions†
A well-designed 3D metal–organic framework with accessible Lewis acid–base sites, [Zn2(PZDC)(1/2ATZ)2(H2O)2·2.5H2O] (H2PZDC = 3,5-pyrazoledicarboxylic acid, 5-ATZ = 5-aminoterazole) abbreviated as Zn(PZDC)(ATZ), was successfully prepared by incorporating zinc(II) ions, 3,5-pyrazoledicarboxylic acid and nitrogen-rich 5-aminoterazole. The existence of abundant Lewis bases can increase the chemical affinity to carbon dioxide, thus resulting in their high CO2 capture ability. Additionally, the heterogeneous Zn(PZDC)(ATZ) catalyst facilitated the CO2 coupling reaction of various epoxides into cyclic carbonates with the aid of Bu4NBr under solvent-free conditions (90 °C, 1 MPa, 6 h); besides, a high TON (131.0) and TOF (21.8 h−1) of propylene carbonates were obtained. Furthermore, the Zn(PZDC)(ATZ) catalyst also showed good chemical stability and recyclability for seven cycles without a significant catalytic loss. What's more, a plausible catalytic mechanism of synergistic effects derived from Zn(PZDC)(ATZ)/Bu4NBr catalysts for CO2 conversion to cyclic carbonate was proposed.