Alumina-Supported Porphyrin Zinc as a Carbonic Anhydrase Mimic: Enhanced CO Hydration Catalysis.

Zinc porphyrin is a promising carbonic anhydrase (CA) mimic for promoting CO absorption, but its application is hindered by poor dispersibility in absorption solutions. To address these challenges, we developed a strategy to impregnate zinc porphyrin on an γ-AlO carrier. The hydrophilic surface groups and porous structure of γ-AlO were expected to enhance both the hydrophilicity and stability of zinc porphyrin. To verify its feasibility, zinc tetraphenylporphyrin (ZnTPP) was chosen as the representative to synthesize ZnTPP/AlO. Characterizations showed that ZnTPP could be loaded into the pores of γ-AlO in a highly dispersed state. Also, ZnTPP/AlO could be uniformly dispersed in the absorption liquid, effectively exposing the Zn active sites and reducing diffusion resistance. CO absorption experiments revealed that ZnTPP/AlO significantly enhanced CO absorption in water, 20 wt % KCO, and 20 wt % monoethanolamine (MEA) solutions, far outperforming original ZnTPP. Density functional theory (DFT) calculations further elucidated the interaction mechanisms, showing that oxygen atoms on γ-AlO stabilize ZnTPP by forming van der Waals and coordination bonds with Zn active sites. Additionally, these oxygen atoms donate electrons to Zn, enhancing its catalytic activity. These findings highlight the effectiveness of this strategy and provide a promising pathway for optimizing other CA-mimics for CO capture applications.