The design of a novel and resistant Zn(PZDC)(ATZ) MOF catalyst for the chemical fixation of CO2 under solvent-free conditions

Abstract

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.