A carbonic anhydrase inspired temperature responsive polymer based catalyst for accelerating carbon capture

•Temperature responsive carbonic anhydrase mimicking compound.•Rate promoter for carbon dioxide (CO2) capture.•Easily recyclable and hydrolytically stable catalysts to promote CO2 capture.

A temperature responsive carbonic anhydrase mimicking compound (PNiPAm-co-CyclenZn) was synthesised and characterized to assess its potential as a rate promoter for carbon dioxide (CO2) capture using solvent absorption. Development of novel rate promoters, such as the catalytic polymer discussed in this study, can improve reaction kinetics and reduce the cost of CO2 capture. Results showed that the lower critical solution temperature (LCST) of PNiPAm-co-CyclenZn is 33.7 °C which is close to the physiological temperature. Above the LCST, PNiPAm-co-CyclenZn undergoes a phase transition from a swollen hydrated state to a shrunken dehydrated state. This property can potentially enable easy separation of PNiPAm-co-CyclenZn from the CO2 loaded solution exiting the absorber column so that it does not enter the high temperature stripping column. In the reaction between CO2 and H2O, the catalysis coefficient at 298 K of PNiPAm-co-CyclenZn was determined to be 380 ± 20 M−1 s−1 at a pH of 7.36 and 2330 ± 40 M−1 s−1 at a pH of 9.06. Arrhenius fitting of the catalysis coefficients showed an activation energy of 60 ± 2 kJ/mol at pH of 7.36. This study presents the first example of a temperature responsive polymeric catalyst for carbon dioxide absorption. The catalyst was developed with the aim of increasing the absorption rates of carbon dioxide in bicarbonate forming amine solutions and carbonate solvents that have slow absorption kinetics.

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