Hydroxyl-ionic liquid functionalized metalloporphyrin as an efficient heterogeneous catalyst for cooperative cycloaddition of CO2 with epoxides

Catalytic fixation of greenhouse gas CO 2 into value-added chemicals under mild conditions was deemed as an effective pathway for carbon emissions mitigation, though facing big challenges. Herein, a novel hydroxyl-ionic liquid functionalized metalloporphyrin (ZnTpyp-IL) catalyst bearing hydrogen bond donor (HBD), Lewis acidic and nucleophilic sites was fabricated and invested in the CO 2 cycloaddition without additive or solvent. The integration of ionic liquid endowed the framework with strong surface affinity to enrich CO 2 molecules, while the cooperative interplay of multiple active sites further promoted the high-selective conversion of epichlorohydrin (ECH). Under optimal conditions (100 °C, 1 MPa, 4 h), the yield of corresponding chloropropene carbonate (CPC) reached 97.1 % (turnover frequency (TOF) = 52.4 h -1 ), far superior to that of bare Tpyp (17.4 %). The preliminary kinetic studies revealed the lower activation energy (59.54 kJ/mol) needed to be overcome in the ring-opening process over ZnTpyp-IL. Moreover, a plausible dual-activation mechanism of hydrogen bonds and Zn centers for epoxides was proposed based on the density functional theory calculation (DFT) to explain the acceleration of rate-determining step. Coupled with the satisfactory reusability and substrate expansibility, the developed ZnTpyp-IL demonstrated its great potential as robust heterogeneous catalyst in the efficient utilization of C 1 resource.