Enzyme-conjugated ZIF-8 particles as efficient and stable Pickering interfacial biocatalysts for biphasic biocatalysis

In this study, a proof-of-concept for constructing efficient and stable biocatalysts is reported for biphasic catalytic reactions, where enzyme-conjugated ZIF-8 particles are utilized as efficient and stable Pickering interfacial biocatalysts. During the preparation of enzyme-conjugated ZIF-8 particles, dopamine modification on the surface of ZIF-8 particles is an essential step, which cannot only manipulate the surface hydrophilicity of ZIF-8 particles but also render surface reactive groups for conjugating enzymes in a green manner. The enzyme-conjugated ZIF-8 particles can be spontaneously assembled at the water/oil interfaces through optimizing their surface hydrophilicity, which then leads to enhanced catalytic activity as a result of much lower external and internal diffusional resistances. Such Pickering interfacial catalysts can be simply recycled and positioned at the water/oil interface via relatively low-speed centrifugation (5000 rpm), thus indicating an ease of separation for the substrate (p-NPP in the oil phase), the product (p-NP in the water phase) and catalysts (as the solid phase). Moreover, as evidenced by a 13-cycle reaction and a 37 day storage test, the robust conjugation of an enzyme on the surface of the particles can effectively protect the enzyme from the organic-solvent stress, thus retaining high catalytic activity.