Regulating the N-functional hydrogen bond donors over magnetic nanoparticles supported imidazole tribromide zinc ionic liquid for CO₂ cycloaddition

The design of catalysts for the mile production of cyclic carbonates by CO₂ cycloaddition is of value. Magnetic polymer nanoparticles-supported imidazole tribromide zinc ionic liquid catalysts, incorporating N-functional hydrogen bond donors (HBD), was successfully accomplished. The correlation between the N-functional HBD and catalytic activity was thoroughly investigated through experimental studies and DFT calculations. The catalyst featuring a secondary amine group (NHM) demonstrated remarkable catalytic performance in CO₂ cycloaddition reactions. Under optimized conditions, including 0.12 mol% catalyst dose, 100 °C, and n_PO:n_CO2 = 1:1.2 for 3 h, a complete conversion was achieved. The exceptional performance of the catalyst was attributed to the multicenter synergistic effect, arising from the appropriate electronegativity, minimal spatial site resistance, a balanced distance between the NHM and imidazolium ion, and the presence of multiple active centers (NHM, Zn²⁺, and Br⁻). The integration of a magnetic component enabled swift separation and exceptional recovery stability over 8 consecutive cycles.