Bioinspired Three-Dimensional Zn-Coordinated Organic Frameworks as Carbonic Anhydrase-Mimics for Efficient Carbon Dioxide Hydration Reactions
The development of efficient enzyme mimics for CO2 hydration remains a critical challenge for industrial carbon capture. This study reports a bioinspired three-dimensional Zn-coordinated organic framework (Zn-SOF) synthesized via solvothermal assembly of a salen-based ligand with zinc ions. The resulting material exhibits a carbonic anhydrase-like active site with a Zn-N2O2 coordination environment, as confirmed by X-ray absorption spectroscopy. The Zn-SOF demonstrates a CO2 hydration rate of 3.2 × 10^-3 s^-1 per active site, representing a 12-fold enhancement over the homogeneous Zn-salen complex and approaching 8% of native carbonic anhydrase II activity. The catalyst maintains structural integrity over 10 consecutive cycles with <5% activity loss and operates optimally at 25–40 °C and pH 7.4–9.0. Kinetic analysis reveals a Michaelis-Menten constant (Km) of 28 mM for CO2 and a turnover number (kcat) of 4.1 s^-1, outperforming benchmark Zn-based mimics. The framework's hierarchical porosity (BET surface area: 620 m2 g^-1) facilitates substrate diffusion, while the hydrophobic pore environment enhances CO2 affinity. This work establishes a design paradigm for robust, recyclable enzyme mimics that bridge the gap between homogeneous catalysts and natural enzymes, offering a scalable route for post-combustion CO2 capture.