Polybenzoxazine bearing phosphonium and phenol functions catalyzed the cycloaddition of CO₂ into epoxide reactions

Polybenzoxazine bearing phosphonium and phenol functions was firstly designed, synthesized, and evaluated for the cycloaddition of CO₂ into epoxide (CCE) reactions. Benzoxazine monomers intrinsically installed with phosphonium halide moiety were thermally polymerized to obtain phenolic-type polybenzoxazines. The bifunctional polybenzoxazine catalyst promoted CCE reactions at 120 °C within 2 h to afford high yields up to 96% under atmospheric pressure. The catalyst was recycled four times and maintained 92% yield. A possible bifunctional catalytic mechanism composed of hydrogen-bonding activation by phenol and co-catalysis by halide was proposed and validated. The easy preparation of the benzoxazine monomers with variety of catalytic moieties, and one-step fabrication of the polybenzoxazines suggest untapped potential of manifold polymeric catalyst design and applications.