Flow-Based Microfluidic Synthesis of Homogeneous Enzyme@MOFs by Biomimetic Mineralisation

Enzyme immobilisation within Metal–organic Frameworks (MOFs) provides a promising strategy for improving enzyme dispersion and local environment control, although the resulting performance depends strongly on the host materials, enzyme type and immobilisation conditions. Conventional in situ biomimetic mineralisation typically produces enzyme–MOF composites (enzyme@MOFs) with irregular morphologies, broad particle size distributions and aggregation, which can compromise catalytic performance and reproducibility. This study presents a flow-based microfluidic biomimetic mineralisation strategy for preparing horseradish peroxidase-encapsulated ZnBDC-NH2 MOF composites. A flow-focusing microfluidic chip containing multiple rectangular baffle structures was designed to enhance transverse mixing, extend the effective residence time, and mitigate clogging during particle formation. Under the selected conditions, homogeneous HRP@ZnBDC-NH2 particles with an average hydrodynamic diameter of 868.5 nm and a polydispersity index of 0.266 were obtained. The homogeneous HRP@ZnBDC-NH2 showed an encapsulation efficiency of 56.17% and a loading content of 1.49%. Michaelis–Menten analysis gave a Km value of 52.49 μM for HRP@ZnBDC-NH2, suggesting improved apparent substrate affinity compared with the corresponding bulk-synthesised sample. The results support the use of baffle-structured microfluidics as a controllable platform for enzyme@MOF synthesis, while further studies on enzyme leaching, reusability, long-term stability and extended chip operation are required to evaluate its operational robustness.