Bowtie-Shaped Bio-Based\nZwitterionic Polymer-Catalyzed\nChemical Fixation of Carbon Dioxide

Developing green and low-cost catalytic\nsystems is highly\ndesired\nin the chemical conversion of carbon dioxide into value-added products.\nA zwitterionic polymer, with a bowknot-like morphology consisting\nof uniform nanosheets, is synthesized from biomass-derived cinnamic\nacid via a simple copolymerization strategy. The as-prepared zwitterionic\npolymer (PEMP) has been employed to catalyze the cycloaddition reaction\nof epoxides and atmospheric CO<sub>2</sub>, affording 9 cyclic carbonates\nwith good to excellent yields under metal-free/solvent-free/cocatalyst-free\nconditions. PEMP with outstanding stability can be reused 5 times\nat least without an obvious loss of catalytic activity. The reaction\nmechanism was elaborately investigated by in situ Fourier transform\ninfrared spectra tests, control experiments, and density functional\ntheory calculations, demonstrating that the catalytic cycloaddition\nof CO<sub>2</sub> and epoxides over PEMP occurs through the preactivation\nof epichlorohydrin. Moreover, it is illustrated that the synergistic\neffect between the carbonate anion and quaternary ammonium cation\non the zwitterionic polymer played a crucial role in promoting the\nactivation of epoxides and CO<sub>2</sub>.