Acid-base bifunctional catalyst: Carboxyl ionic liquid immobilized on MIL-101-NH2 for rapid synthesis of propylene carbonate from CO2 and propylene oxide under facile solvent-free conditions

Abstract

In terms of ‘green chemistry’ and ‘atom economy’, the cycloaddition of CO2 to yield cyclic carbonate without any additive is an eco-friendly way to utilize CO2. Unfortunately, the low CO2 capture quantity of common catalysts limited its catalytic efficiency. Herein, a novel acid-base bifunctional catalyst was successfully prepared by immobilizing ionic liquid on MIL-101-NH2 (IL/MIL-101-NH2) and tested for propylene carbonate (PC) rapid and facile synthesis from CO2 and propylene oxide (PO). The synergetic interaction between Lewis base with strong CO2 chemical capture capacity and Brønsted acid with strong hydrogen bond donor leads to the high catalytic efficiency of IL/MIL-101-NH2 for carbonate synthesis from CO2 and PO without any additive. The immobilization mode between MIL-101-NH2 and IL is energetically supported by the density functional theory (DFT) calculations. This design idea of specific catalyst and the acid-base synergetic strategy provides new insights into the design of powerful catalyst systems for the CO2 conversion.