Mechanistic insights on CO2 utilization using sustainable catalysis

Abstract

We reported on sustainable, one-pot synthesized caffeine-based compounds as effective, bifunctional, heterogenous, hydrogen-bond-donor organocatalysts for the cycloaddition of CO₂ with several epoxides, supported by a mechanistic study and verified by density functional theory calculations. Two reaction intermediates were isolated during the catalytic cycle: the first involving hydrogen bonding between caffeinium bromide and epichlorohydrin upon exchanging Br⁻ with PF₆⁻, and the second comprising of the nucleophilic attack of Br⁻ followed by ring opening, as deduced from the appearance of a peak corresponding to the C–Br bond in the ATR-FTIR spectrum in the absence of CO₂. In this respect, most of the literature is based on postulated mechanisms, racing to achieve lower working conditions, urging us to dig deeper to understand the aforementioned reaction.