Immobilization of lipase mediated by L-histidine-based ionic liquid as a bridge on magnetic COF and its application in isoamyl acetate synthesis

L -histidine ionic liquid modified magnetic COF was successfully fabricated. • Covalent modification of supports with IL optimized the enzyme microenvironment. • Introduction of IL enhanced the activity and stability of immobilized lipase. • IL boosted lipase-substrate affinity and catalytic efficiency. • Magnetic responsiveness improved the separation efficiency of immobilized lipase. This study proposes an innovative immobilized lipase construction strategy to address the low activity and poor stability limitations of current biocatalysts for flavor ester synthesis. L -histidine-based ionic liquid (IL) is covalently grafted onto the surface of magnetic covalent organic framework (COF) via Schiff base reaction, and porcine pancreatic lipase (PPL) is further covalently immobilized on the composite carrier through amide bond coupling. The resulting Fe₃O₄@COF-IL-PPL shows 1.6-fold higher catalytic activity and 2.3-fold better thermal stability than free PPL, and 32% higher activity retention after cycles than PPL immobilized on IL-free COF carrier. Its optimal reaction pH and temperature are 7.5 and 50 °C respectively, maintaining 86% of initial activity at 60 °C and 76% activity after 6 h incubation at 50 °C. Under n-hexane reaction system, the isoamyl acetate yield reaches 87.4% under optimal conditions, and the biocatalyst retains 71.4% activity after 10 consecutive isoamyl acetate synthesis cycles. Although the additional preparation steps and higher cost of the support need to be considered for industrial applications, the improved catalytic performance of Fe 3 O 4 @COF-IL-PPL verified the effectiveness of IL surface modification strategy, and the system can be further extended to solvent-free systems to verify its broader applicability.