Integrating enzymatic activity into highly emissive metal-organic frameworks derived from AIE ligands via horseradish peroxidase immobilization for dual-mode optical sensing

HRP was covalently immobilized on MAF to form a biocomposite with high activity and fluorescence. • HRP@MAF exhibited a remarkable fluorescence quantum yield of 97.77%. • HRP@MAF showed superior substrate affinity with a Km value 25-fold lower than HRP. • A dual-mode colorimetric/ratiometric fluorescent sensor was developed for histamine. Integrating strong fluorescence and efficient biocatalysis within a single metal-organic framework (MOF) is attractive for advanced optical sensing. Herein, a highly emissive metal-organic framework (denoted as MAF) was constructed using ligands with aggregation-induced emission (AIE) properties, followed by horseradish peroxidase (HRP) immobilization to yield HRP@MAF with high catalytic activity and strong fluorescence. The resulting HRP@MAF exhibited a fluorescence quantum yield of 97.77%. Benefiting from the high surface area and porous structure of MAF, HRP@MAF showed markedly improved stability and substrate affinity toward 3,3′,5,5′-tetramethylbenzidine (TMB), with a K m value 25-fold lower than that of free HRP. Based on its catalytic and optical properties, a colorimetric/ratiometric fluorescence sensor was developed for histamine detection with detection limits of 1.71 μM and 0.56 μM, respectively. In addition, smartphone-integrated on-site detection was achieved with linear ranges of 10–1000 μM for the colorimetric mode and 1–1000 μM for the ratiometric fluorescence mode. This work establishes an effective strategy for constructing multifunctional sensing platforms by coupling AIEgens derived highly emissive MOFs with immobilized enzymes. Download: Download high-res image (151KB) Download: Download full-size image