Covalent Organic Framework Aerogels with Tailored Microenvironments for Optimizing Enzyme Immobilization and Catalytic Performance^†

Enzyme immobilization is a crucial step in advancing the industrial application of biocatalysts. Achieving effective enzyme encapsulation and precise tailoring of the enzyme microenvironment is essential for maximizing catalytic performance, yet remains a challenge. In this study, we synthesized hierarchically porous covalent organic framework (COF) aerogels, incorporating alkyl chains of varying lengths on the framework, to enable efficient enzyme immobilization, facilitate mass transfer and fine-tune the microenvironment. The introduction of alkyl chains modulated enzyme-COF interactions, inducing interfacial activation and promoting open enzyme conformation with more accessible active sites. Notably, increasing the length of alkyl chains strengthened enzyme-COF interactions, and the enzyme immobilized on the COF aerogel with the longest alkyl chains (C6) showed the highest activity and stability, achieving more than twice the conversion of the free enzyme even at low temperatures (0–20 °C) and maintaining 90% of its initial conversion after thermal treatment at 80 °C. Furthermore, COF aerogel-immobilized enzymes maintained high conversion in continuous-flow reactions for 8 h, demonstrating operational robustness. The generality of this approach is validated with multiple lipases, showing enhanced activity. This study highlights the potential of functionalized COF aerogels as a versatile and robust platform for developing high-performance biocatalysts.