Bridging hydroxyl-functionalized MgO as an efficient heterogeneous hydrogen-bond-donor catalyst for CO2 fixation into propylene carbonates

Employing heterogeneous hydrogen-bond-donor (HBD) for the efficient conversion of epoxides and CO₂ into cyclic carbonates is highly desired yet challenging in the field of green chemistry. Herein, we report a bridging hydroxyl-functionalized MgO serve as an efficient heterogeneous HBD catalyst to facilitate the ring-opening of epoxides for cycloaddition with CO₂. MgO with various density of HBD (MgO-H) were constructed by adjusting the equilibrium of dehydration reaction via tuning calcination temperature distribution of MgO particles. Consequently, MgO-H shows significantly increased propylene epoxide conversion from 65.4 % to 96.8 % while maintaining high propylene carbonate selectivity (98.5 %) in the absence of alkaline halides. Furthermore, based on multiple in situ techniques and the DFT calculations, it is found that the HBD could assisted with the Mg²⁺–O^2- Lewis acid-base pairs to activate the epoxides. This work presents an efficient strategy for modifying the hydroxyl groups on oxide surfaces to engineer heterogeneous HBD catalysts for CO₂ cycloaddition.