Defect-coupled cooperative catalysis enables a highly active MOF-on-MOF nanozyme for direct discrimination of dihydroxybenzene isomers

Abstract

The development of MOF-on-MOF architectures has emerged as a powerful strategy to expand the compositional diversity and hierarchical structures of MOFs, providing new opportunities to tailor their physicochemical properties and catalytic performance. Despite these advantages, their utilization in constructing oxidase-like (OXD-like) nanozymes with cooperative catalytic characteristics remains limited. Herein, a highly active MOF-on-MOF nanozyme was rationally constructed by integrating ZIF-67 with a benzoic acid (BA)-modified Ce-MOF, where ligand-modulated coordination defects were introduced into the heterostructure. Within this heterostructure, the spatially coupled Ce and Co centers enabled defect-coupled cooperative catalysis, which enhanced O₂-involved oxidation capability and facilitated electron transfer during substrate oxidation, thereby improving OXD-like activity. Meanwhile, oxidized ABTS exhibited distinctly different reaction behaviors toward dihydroxybenzene isomers on the nanozyme surface. Notably, the reaction between ABTS and resorcinol (RS) generated a characteristic absorption peak at 530 nm, and the absorbance ratio at 530 nm and 417 nm served as a reliable response signal, enabling rapid and sensitive discrimination of RS from catechol (CA) and hydroquinone (HQ). This defect-coupled MOF-on-MOF nanozyme was validated to be an efficient nanozyme with simultaneously high catalytic activity and isomer target discrimination capability, which might provide a reference for the indigenous construction of powerful nanozymes.