Metal‐Free Polymeric Boron Catalyst: Clustering Effect Enables Highly Efficient CO 2 Conversion to Polycarbonates

ABSTRACT Borane element as Lewis acids plays an indispensable role for epoxide/CO 2 copolymerization among metal‐free catalysts. Hence, we precisely designed a polymeric boron catalyst (PBBN) by anchoring multiple borane active centers onto the polyethylene chain via one‐step hydroboration reaction. PBBN shows better air and moisture tolerance compared to common borane‐based small‐molecule catalysts, thereby ensuring favorable safety profiles. Furthermore, it exhibits excellent catalytic activity in both the homopolymerization of PO and the copolymerization of CHO/CO 2 owing to the “clustering effect” arising from the aggregation of boron centers. Remarkably, PBBN demonstrated exceptional proton tolerance in poly(cyclohexene carbonate) diol (PCHCDL) synthesis with each boron atom capable of withstanding at least 50 equivalents of 1,4‐butanediol (BDO, equivalent to 100 proton equivalents), showing promising application potential in the polycarbonate diol synthesis.