A confined catalysis strategy: Lewis acid-base (B/Br) and hydrogen bond donor (-OH) multi-functionalized core-shell catalyst for CO2 cycloaddition

Abstract

In recent years, a significant number of metal-based catalysts were synthesized for the CO2 cycloaddition reaction. However, the leaking of active metal elements resulted in various environmental issues. To prevent the loss of active components and enhance the catalyst lifespan, a confined catalysis strategy involving a multi-functionalized core-shell catalyst with Lewis acid-base (B/Br) and hydrogen bond donor (-OH) was designed. It was noteworthy that B-mSiO2@MCM-IMOH featured multifunctional catalytic active sites, including Lewis acid-base (B/Br) and hydrogen bond donor (-OH), and the cooperative effect of B, Br and -OH significantly improved the catalytic activity. Therefore, B-mSiO2@MCM-IMOH demonstrated outstanding catalytic performance for the CO2 cycloaddition reaction. In addition, the core-shell molecular sieve, serving as a confined catalytic carrier, effectively enhanced the stability and recyclability of the catalyst. Utilizing DFT calculations, a cooperative catalytic mechanism was proposed involving Lewis acid-base (B/Br) and hydrogen bond donor (-OH). The synergistic interaction between B/Br and -OH markedly reduced the energy barrier for the ring-opening of propylene oxide from 58.6 kcal·mol−1 to 21.5 kcal·mol−1, thus facilitating the PO-CO2 cycloaddition reaction.