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Keywords:

  • amino acids;
  • cobalt;
  • carbon dioxide fixation;
  • metal–organic frameworks;
  • microwave chemistry

Abstract

The sulfonate anion is proposed as a remarkable partaker in catalyzing epoxide–CO2 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)(H2O)}H2O]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 CO2 by the sulfonate group. The involvement of SO3 anions as basic sites in 2 D-CCB is ascertained from the initial rate (r0) for catalyzing Knoevenagel condensation reactions and by using CO2 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.