Crystal Phase Transition-Driven Integration of Enzymes into 2D Metal-Organic Frameworks

In situ encapsulation of enzymes within a metal-organic framework (MOF) represents a promising technique for engineering robust biocatalysts. However, the success of enzyme encapsulation is often constrained by intricate interfacial interactions between enzyme surfaces and MOF precursors, limiting the versatility of this MOF method. Herein, we introduce a phase transition strategy for encapsulating enzymes within a Zn-HHTP framework, demonstrating its effectiveness across a wide range of enzymes irrespective of their surface chemistry. In this approach, enzyme molecules are preloaded in a zinc oxide (ZnO) template through a simple yet efficient coprecipitation process, followed by a ZnO-to-Zn-HHTP MOF crystal phase transition in the presence of ligand precursors, resulting in the formation of a quasi-mesoporous hybrid Zn-HHTP MOF inside, for which the original enzymes are preserved. The long-range ordered quasi-mesopore channels enhance substrate accessibility to the immobilized enzymes, endowing enzyme@Zn-HHTP with higher catalytic activity compared to enzymes immobilized within the well-known MOF, ZIF-8, which has narrow apertures. Additionally, the resultant enzyme@Zn-HHTP exhibits exceptional structural stability across a broad pH range (3-14), and Zn-HHTP can provide robust protection against enzyme denaturation by heat, organic solvents, and proteases. This work offers a facile and reliable phase transition strategy for synthesizing active and robust MOF biocatalysts, advancing biocatalysis across various fields.