Abstract
Zinc porphyrin is a promising carbonic anhydrase (CA) mimic for promoting CO2 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-Al2O3 carrier. The hydrophilic surface groups and porous structure of γ-Al2O3 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/Al2O3. Characterizations showed that ZnTPP could be loaded into the pores of γ-Al2O3 in a highly dispersed state. Also, ZnTPP/Al2O3 could be uniformly dispersed in the absorption liquid, effectively exposing the Zn2+ active sites and reducing diffusion resistance. CO2 absorption experiments revealed that ZnTPP/Al2O3 significantly enhanced CO2 absorption in water, 20 wt % K2CO3, 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-Al2O3 stabilize ZnTPP by forming van der Waals and coordination bonds with Zn2+ active sites. Additionally, these oxygen atoms donate electrons to Zn2+, enhancing its catalytic activity. These findings highlight the effectiveness of this strategy and provide a promising pathway for optimizing other CA-mimics for CO2 capture applications.
Published Version
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