Synthesis of a Zn(II)-2-aminoimidazole Framework as an Efficient Carbonic Anhydrase Mimic

Carbonic anhydrase (CA) plays a crucial role in the CO₂ capture processes by catalyzing the hydration of CO₂. In this study, we synthesized a bioinspired carbonic anhydrase Zn-MOF (metal-organic framework) incorporating 2-aminoimidazole and Zn²⁺ as initial constituents. The synthesized Zn-MOF exhibited promising potential for efficiently catalyzing the CO₂ hydration. Structural analyses such as SEM, XRD, and BET confirmed that the Zn-MOF crystal consisted of stacked grains with an average size of approximately 36 nm, forming a micron-sized spherical structure. Functionally, Zn-MOF exhibited effective catalytic activity toward both CO₂ hydration and ester hydrolysis. The introduction of amino groups significantly enhanced the esterase activity of Zn-MOF to 0.28 U/mg at ambient temperature, which was twice that of ZIF-8. Furthermore, the introduction of amino groups resulted in remarkable hydrothermal stability, with the esterase activity reaching 0.72 U/mg after undergoing hydrothermal treatment at 80 °C for 12 h. Additionally, Zn-MOF exhibited enhanced capability in CO₂ hydration at a pH value exceeding 8.5. After six repeated uses, ZIF-8 and Zn-MOF retained approximately 68 and 65% of their initial enzyme activity, respectively, underscoring the potential practical applicability of Zn-MOF in industrial CO₂ capture processes. This work showcases the development of a novel Zn-MOF crystal as an efficient CA mimic, effectively emulating the active sites of natural CA using 2-aminoimidazole as a coordinating ligand for Zn²⁺ coordination. These findings not only advance the field of innovative enzyme mimics but also pave the way for further exploration of industrial CO₂ capture catalysts.