Hypercrosslinked ionic polymers constructed by ionic cross-linkers and Bronsted acid for catalytic cycloaddition of low-concentration CO2 with epoxide under atmospheric pressure

Abstract

The capture and conversion of low-concentration CO₂ into high value-added products under mild conditions remains a major challenge. In this work, an additive/metal/solvent-free catalytic transformation between epoxides and low-concentration CO₂ under atmospheric conditions is achieved by using hypercrosslinked ionic polymers (IMPy-HIP or BPy-HIP) as catalysts prepared by an one-pot Friedel–Crafts alkylation between an imidazolium-based ionic linker and 1, 1′-binaphthyl-2, 2′-diyl hydrogenphosphate (BNDHP, a Bronsted acid, strong hydrogen bond donor). The HIPs bearing a strong hydrogen bonding site (ArPO₃OH), active cations (imidazolium) and nucleophilic counterion (Cl⁻) demonstrate highly catalytic efficiency and stable recyclability for low-concentration CO₂-epoxide cycloaddition. The experiment results combining with DFT theoretical calculations reveal that the high performance of this catalyst attributes to the cooperation of the Bronsted acid site (P-OH), basic pyridine N and ionic site. In addition, the catalyst shows excellent structural stability and substrate universality, and it can be easily separated by centrifugation and reused for five runs without significant decrease in catalytic performance.