Comparative study on the catalytic hydration of carbon dioxide by catalysts that mimic carbonic anhydrase prepared with zinc salts

Recently, a new catalyst that mimics carbonic anhydrase (CA) was constructed by the self-assembly of histidyl bolaamphiphilic molecules and a Zn ion cofactor. The catalytic Zn ion complex in a tetrahedral coordination geometry is composed of self-organized histidyl imidazoles and a single hydroxide ion. However, the Zn-hydroxide coordination, the key structure of the catalytic analogue, is disturbed by the pairing anion of the Zn salt. Here, the performances of the CA-mimicking catalysts prepared from various Zn salts were examined along with CO₂ hydration. Among the Zn salts with different anions, Zn(OH)₂ showed the highest catalytic performance with increased CO₂ hydrolysis activity. Spectroscopic and thermodynamic analyses proved the formation of histidine-Zn-hydroxide coordination with a lowered activation energy if Zn(OH)₂ was used. With regard to the anion interaction with the Zn ion, the catalytic performance is inversely proportional to the solution dissociation energy of the Zn salt. Zinc about it: Among the various Zn salts used for the preparation of a catalyst that mimics carbonic anhydrase (CA), Zn(OH)₂ shows the highest catalytic performance with increased hydrolysis activity as it minimizes the interference of the counter anion. Spectroscopic analysis and calculated activation energies along with practical CO₂ sequestration of the CA-mimetic catalysts confirms catalysis inhibition by Zn-binding anions.