Study on the zinc porphyrins as potential carbonic anhydrase mimics for promoting CO2 absorption in K2CO3 solution

Abstract Zinc porphyrins, boasting a coordination environment akin to that of carbonic anhydrase (CA), coupled with excellent structural stability, built-in hydrophobic pocket, and relatively low charge of center Zn2+, offer promise as CA-mimics for industrial CO2 capture. In validation, three representative zinc porphyrins—zinc porphin (ZnP), zinc protoporphyrin IX (ZnPP), and zinc meso-tetrakis(N-methylpyridinium-4-yl) porphyrin (ZnTMPyP) were synthesized and tested performance in water and 2 wt.% K2CO3 solution. Results showed that zinc porphyrins enhanced CO2 absorption by up to 44.25% in water and 46.77% in K2CO3 solution, which surpassed zinc cyclen (ZnC), one of the most efficient CA-mimics reported, by 1.31-1.53 times even at significantly lower dosages. Besides, they demonstrated excellent stability and reusability. Calorimetry and density functional theory (DFT) confirm their CA-mimetic activity and CA-like CO2 hydration pathway. High dispersion, lowest Zn2+ charge, and abundant CO2 adsorption sites endow ZnPP with the highest catalytic activity in K2CO3 solution.