Pillared Cobalt–Amino Acid Framework Catalysis for Styrene Carbonate Synthesis from CO₂ and Epoxide by Metal–Sulfonate–Halide Synergism

The sulfonate anion is proposed as a remarkable partaker in catalyzing epoxide–CO 2 cycloaddition for cyclic carbonate synthesis. The role is illustrated by the concerted action of a sulfonate‐rich cobalt–amino acid framework catalyst [{Co(4,4′‐bipy)( L ‐cys)(H 2 O)} ⋅ H 2 O] n (2 D‐CCB) and a quaternary ammonium bromide co‐catalyst in synthesizing styrene carbonate (SC) at a turnover number of 228. SC yield at atmospheric pressure is presumed to result from the activation of CO 2 by the sulfonate group. The involvement of SO 3 − anions as basic sites in 2 D‐CCB is ascertained from the initial rate ( r 0 ) for catalyzing Knoevenagel condensation reactions and by using CO 2 temperature programmed desorption. Microwave pulses are used for synthesizing 2 D‐CCB at a rate that is 288‐fold faster than conventionally employed solvothermal methods. Unambiguous evidence for the pulsating role‐play of sulfonate groups in 2 D‐CCB is perceived by comparing the activity of an analogous metal organic framework (3 D‐CCB) in which the sulfonate oxyanions are jammed by coordination with cobalt. 2 D‐CCB is analyzed for heterogeneity, and reused four times.