[Research progress on porous framework material-based immobilized enzyme biosensors for pesticide residue analysis]

Pesticide residues pose a persistent threat to ecosystem safety and human health，creating an urgent need for rapid detection techniques that combine high sensitivity with portability. Enzyme-based biosensors，with their excellent molecular recognition capabilities，have emerged as promising tools； however，their practical application is often hampered by the inherent instability of natural enzymes，including susceptibility to denaturation，limited operational pH and temperature ranges，and poor reusability. In this context，porous framework materials-specifically metal-organic frameworks，covalent organic frameworks，and hydrogen-bonded organic frameworks-have attracted considerable attention as ideal supports for enzyme immobilization. These materials offer ultrahigh specific surface areas，tunable pore architectures，and robust chemical stability，which together can significantly enhance enzyme catalytic activity，operational stability，and substrate selectivity via confinement effects，protective shielding，and microenvironment modulation. This review systematically summarizes recent progress in the development of immobilized-enzyme biosensors based on porous framework materials for pesticide monitoring. We first categorize three main enzyme immobilization strategies： surface adsorption，post-synthetic infiltration，and in situ encapsulation. Surface adsorption attaches enzymes via weak interactions，offering simplicity but potential leaching； post-synthetic infiltration exploits pore size matching to achieve high loading； and in situ encapsulation entraps enzymes during framework growth，conferring superior protection. For each strategy，we discuss characteristic features regarding loading efficiency，enzyme stability，and substrate selectivity，as well as applicability to different enzyme-framework combinations. We then provide a detailed account of sensing modalities based on colorimetric，fluorescent，electrochemical，and chemiluminescent signal transduction mechanisms. Colorimetric sensors utilize enzyme inhibition to produce visible signals，fluorescent sensors rely on signal changes from confined fluorophores，electrochemical platforms transduce enzymatic reactions into electrical outputs，and chemiluminescent systems offer low-background light emission. The underlying response principles，signal amplification strategies，and analytical performance metrics-such as detection limits，linear ranges，and selectivity-are critically examined. Furthermore，we address key challenges hindering on-site deployment： tolerance to complex sample matrices （e.g.，fruit juices，soil extracts） that cause nonspecific interferences； simultaneous recognition of multiple pesticide residues requiring multi-enzyme cascades or array-based differentiation； green and scalable synthesis of framework-enzyme composites under mild conditions； and integration into intelligent sensing systems （e.g.，smartphone-based readers，microfluidics，and wireless data transmission）. Finally，we propose future research directions aimed at overcoming these obstacles. By bridging materials chemistry and analytical science，this review is intended to provide a theoretical basis and design references for the development of highly reliable，field-deployable rapid detection technologies for pesticide residues，ultimately contributing to food safety and environmental protection.