Understanding the Ingenious Dual Role-Playing of CO₂ in One-Pot Pressure-Swing Synthesis of Linear Carbonate

CO₂, as an engaging C1 building block, shines brightly in green conversion; besides, its unique identity as an acidic molecule is worthy of further development. Here, a novel mode of CO₂ utilization was explored to play a dual role in the one-pot pressure-swing synthesis of dimethyl carbonate (DMC) over 2-hydroxypyridine anion functionalized poly(ionic liquid)s (OPy-PILs), that is, CO₂ could act as both a raw material of coupling reaction and an acidic inhibitor of side-reaction. Specifically, OPy-PILs, constructed by free radical copolymerization followed by ion exchange, were applied to the one-pot coupling reaction of CO₂, epoxide, and CH₃OH. As an efficient heterogeneous catalyst, OPy-PILs could cover basic sites with acidic CO₂ during the insertion of activated CO₂ into epoxide by intermediate [OPy-CO₂^-] so as to reduce the yield of the epoxide alcoholysis side-reaction from 27 to 12%. Moreover, various comparative experiments fully exhibited the high activity and stability of OPy-PILs, and theoretical calculations convincingly explained the dual role-playing of CO₂ in a one-pot pressure-swing reaction. This work paves a novel avenue for the deeper exploration of the CO₂ utilization potential in the catalytic process.