Zinc Nanobiohybrids for the Photocatalytic Conversion of CO2 to Bicarbonate

Given the increasing global carbon dioxide emissions and the urgent need to mitigate climate change, the development of efficient and sustainable carbon dioxide (CO2) conversion strategies has garnered significant attention. In this work, we present, for the first time, the synthesis and design of photocatalytic zinc nanobiohybrids (enzyme-Zn nanostructured hybrid materials) for CO2 conversion under sustainable conditions (aqueous medium at room temperature). We tested different proteins as scaffold, varying nature, behavior, and size, in order to find the optimal ones which could mimic natural specific enzyme activities in the CO(2 )transformation. Depending on the protein employed, different ZnO nanocloud-like structures were formed, influencing their catalytic activities. These structures were evaluated in the model reaction of the selective hydrolysis of p-nitrophenyl propionate (pNPP) to p-nitrophenol (pNP), where Zn coordination with the protein conferred esterase-like activity. Additionally, the synthesized Zn-protein hybrids demonstrated activity in the hydrolysis of CO2 to bicarbonate, exhibiting carbonic anhydrase-like activity. Zn nanobiohybrids also exhibited photocatalytic properties, with conversion efficiencies varying based on the light source used. Notably, Zn-CALB showed the best photocatalytic performance: using ultraviolet (UV) light increased bicarbonate conversion by 2 times (61 ppm/h) compared to natural light (33 ppm/h), and using Xe light increased this value by 2.5 times (83 ppm/h).