Facile Construction of Stable Hierarchical Porous Metal–Organic Frameworks for In Situ Immobilization of β-Glucosidase Based on Competitive Coordination and Selective Etching Strategies

Abstract

Metal–organic frameworks (MOFs) have attracted considerable attention as promising platforms for enzyme immobilization due to their high porosity and ease of preparation. However, the economy and greenness of the MOF synthesis process and the stability of the MOF as well as the microporous structure of MOFs limiting the accessibility of the enzyme and substrate significantly affect their practical applications. Here, based on a competitive coordination and selective etching strategy, we propose a general, simple, fast, low-cost, reproducible, and high-yield synthesis technique for MOF-immobilized enzymes. In the aqueous phase at room temperature, we achieved rapid encapsulation of β-glucosidase (β-G) in MOF-74-2-MI by using 2-methylimidazole (2-MI) as a nucleation accelerator modulator. Followed by selective etching with tannic acid (TA), a hierarchical porous composite, β-G@TA-MOF-74-2-MI, was successfully formed. The results showed a significant increase in mesopore and macropore volumes, leading to a remarkable 6.41-fold enhancement in catalytic activity compared to the nonetched composite. Additionally, it exhibited superior temperature resistance and organic solvent tolerance compared with the free enzyme, along with outstanding cycling, storage, and crystallization stability. This work represents a significant advance in the controlled synthesis of hierarchical porous enzyme@MOF composites, which opens new possibilities for the efficient biocatalysis of macromolecular substrates.