(48g) CA@ZIF-L-Stabilized Pickering Interfacial Catalytic System for Efficient CO2 Conversion

Enzymatic catalysis offers a green and potent alternative for efficient CO₂ conversion due to its high selectivity and specificity, high efficiency, and mild operational conditions. Carbonic anhydrase (CA) enzyme-based absorption technology for CO₂ capture has been intensively investigated. The main issue related to this method is the activity, stability and reusability of the CA enzyme in vitro. To address this issue, CA@ZIF-L-stabilized Pickering interfacial catalytic system was constructed. In detail, CA enzymes were embedded into zeolitic imidazolate framework-L (ZIF-L) particles through biomimetic crystallization. The as-synthesized CA@ZIF-L particles were then spontaneously assembled into capsule at the interface between the oil phase (hexadecane) and water phase during the formation of Pickering emulsions. CA@ZIF-L-stabilized Pickering interfacial catalytic system was finally constructed to convert CO₂ to bicarbonates. The performance of the system was evaluated by adding calcium ions to form calcium carbonate.

The results showed that CA could rapidly initiate the crystallization of ZIF-L to form CA@ZIF-L particles under mild aqueous conditions. The immobilization efficiency of CA could be above 90%. The synthesized CA@ZIF-L, which was served as a solid emulsifier to stabilize Pickering emulsion with its self-assembly properties at the oil-water interface, exhibited excellent catalytic activity in Pickering interfacial reaction and the corresponding cyclic performance. In detail, CA@ZIF-L-stabilized Pickering interfacial catalytic system exhibited higher catalytic efficiency than that of free CA@ZIF-L mainly because of the shortened diffusion path of CO₂ from gas phase to enzyme active center. The production rate of CaCO₃ through Pickering interfacial catalysis reached 2.73 mg min^-1, which is 1.14 times higher than free CA@ZIF-L. In the cycling experiment, about 96.2% of conversion efficiency could be retained for our system after 6 times recycling. These findings above implies that the system we constructed exhibits high activity and stability, particularly, superior recyclability for conversion of CO₂ into CaCO₃.