Bimetallic zeolitic imidazolate frameworks Co/ZIF-8 crystals as carbonic anhydrase-mimicking nanozyme

Zeolitic imidazolate frameworks (ZIFs) materials are known for their excellent stability and their ability to provide an adjustable, controllable structure. The precise assembly of metal nodes and ligands in ZIFs enables them to possess active centers that closely resemble those found in natural enzymes. Building upon this, the objective of this study was to mimic the catalytic active center of natural carbonic anhydrase (CA) by employing defect coordination on the outer surface of bimetallic Co/ZIF-8 crystals. The synthesis process was meticulously controlled through the introduction of cobalt ions, resulting in the creation of a biomimetic CA with remarkable stability and catalytic prowess. The bimetallic Co/ZIF-8 nanozyme exhibited catalytic properties similar to those of natural enzymes. It efficiently facilitated the CO2 hydration reaction and demonstrated the ability to catalyze the reverse reaction. The esterase activity of all Co/ZIF-8 nanozymes was higher than that of the original ZIF-8 at room temperature. Notably, these nanozymes exhibited an impressive maximum esterase activity of 3.77 U/mg at 80 ℃, which surpassed the levels observed in natural CA. This enhancement can be attributed to the boosted catalytic activity of Co/ZIF-8, stemming from the introduction of metal ion doping, which increased the potential difference between bimetallic active centers and facilitated efficient charge transfer. Furthermore, thanks to the unique activation mechanism inherent in the structure of Co/ZIF-8, the esterase activity not only remained unaffected after 24 h of hydrothermal treatment, but also experienced a significant enhancement. This article represents a valuable breakthrough in the regulation and modification of ZIF-8, resulting in the fabrication of an efficient bimetallic Co/ZIF-8 nanozyme for CA-mimicking. These findings hold immense significance for further research and development in the realm of industrial CO2 capture catalysts.