Mechanistic insights into bioelectrocatalytic activity of encapsulated enzyme in metal–organic frameworks and its tandem catalysis with Prussian-blue nanoparticles

The enhanced stability of enzyme@metal-organic framework (MOF) systems significantly benefits bioelectronic-device applications; however, the optimization of their bioelectrocatalytic activity remains underexplored. In this study, we systematically refine the synthesis parameters of enzyme@MOFs and elucidate their bioelectrocatalytic mechanisms using zeolite-imidazole frameworks (ZIF) as a matrix. Their bioelectrocatalytic activities are assessed via direct hydrogen peroxide (H₂O₂) oxidation and H₂O₂ reduction involving tandem catalysis with Prussian-blue nanoparticles (PBNP). The results indicate that a glucose oxidase loading ratio of 10 % relative to the ligand ratio yielded optimal glucose detection. A leaf-like ZIF-based encapsulation matrix demonstrates significantly higher catalytic activity than a sodalite ZIF. Metal-ion variations significantly affect the catalytic performance of the encapsulated enzymes. Co performs better than Zn not only under high applied potentials but also in tandem catalysis with PBNP. Moreover, introducing a conductive filler enables electrical connection to the PBNP located near the encapsulated enzyme, which despite being favorably exposed to a high local concentration of H₂O₂ but had limited participation in the tandem catalysis reaction owing to the low conductivity of the system, thus resulting in a 6.66 ± 0.38-fold increase in catalytic current. This study provides critical mechanistic insights into the bioelectrocatalytic behavior of enzyme@MOFs, thus expanding beyond the conventional focus on enzyme stability enhancement.