PIL@NENPs composite as a synergetic heterogeneous catalyst to enhance the efficiency of CO2 cycloaddition with epoxides

Abstract

The conversion CO2 into highly value-added chemicals requires the development of efficient heterogenous catalysts in the cycloaddition reaction. Herein, the covalent integration strategy of amino-functionalized poly(ionic liquid)s (PIL-NH2HBr) with nitrogen-enriched nano-porous polytriazines (NENPs) was used to synthesize a novel hybrid catalyst, labelled as PIL@NENPs. Several characterization techniques were used to confirm the effective synthesis of PIL-NH2HBr, NENPs and PIL@NENPs composites. Through the PIL-NH2HBr surface integration, the CO2 adsorption capacity of NENPs was greatly improved in the PIL@NENPs composites. The catalytic activity studies shown that the PIL@NENPs exhibited better catalytic activity than PIL-NH2HBr and NENPs in CO2 cycloaddition reaction due to their synergetic effects. Moreover, the PIL@NENPs composite was found to be very easy to separate, had shown good stability and recyclability, and very effective for a variety of epoxides in the CO2 cycloaddition reaction. The Density Functional Theory (DFT) calculations further revealed that the epoxides were activated by hydrogen bond donor (HBD) groups and Br anions whereas the CO2 was activated by N sites. Finally, combining the DFT calculations and activities of different catalysts, a possible reaction mechanism for CO2 cycloaddition catalyzed by PIL@NENPs was proposed.