A halogen-free hyper-crosslinked ionic polymer for efficient multi-conversion of CO2 into carbonates under mild conditions, with a combination of theoretical study

Abstract

Designing catalysts that can efficiently convert CO2 into carbonates remains a challenge. Herein, the multifunctional CO2 affinity hyper-crosslinked ionic polymer was synthesized through self-condensation, quaternization, and ion exchange. The catalyst structure was characterized by FT-IR, TGA, NMR, XPS, and electron microscope spectra. The catalysts have a porous morphology, exhibiting a specific area of 542.2 m2/g and a CO2 adsorption capacity of 0.042 g/g. The CO2 cycloaddition with epichlorohydrin (ECH) can reach a yield of 93 % under metal- and solvent-free conditions. Meanwhile, the transesterification yield of dimethyl carbonate (DMC) between propylene carbonate (PC) and methanol was 62 % under ambient conditions and 83 % at 60 °C. Besides, the catalyst exhibited expansion of up to 16 substrates and no significant loss of activity after 6 cycles. Furthermore, the mechanism was evidenced by the combination of experimental studies and DFT-based calculations, revealing a synergistic effect between the active groups of the two reactions. This work emphasized the pathway that can simultaneously promote the formation of carbonates by both CO2 cycloaddition and transesterification under mild conditions.