Fabrication of 2D Bimetallic Metal-Organic Frameworks with Enhanced Oxidase-Like Activity for AA/ALP Sensing and Antibacterial Application

Nanozymes have garnered significant interest in sensing and antibacterial applications. In this work, a two-dimensional (2D) bimetallic cobalt/copper-based metal-organic framework (Co/Cu-MOF) was synthesized for the first time via a simple and economical one-step co-precipitation method at room temperature. The as-prepared Co/Cu-MOF showed prominent oxidase (OXD)-like activity, effectively catalyzing the decomposition of dissolved oxygen (O ₂ ) to produce superoxide anions (•O ₂ ⁻ ) and singlet oxygen ( ¹ O ₂ ). These reactive oxygen species (ROS) subsequently oxidized the colorless chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) into its blue oxidation product (oxTMB) without the addition of H ₂ O ₂ , yielding a characteristic absorption peak at 652 nm. The presence of ascorbic acid (AA) reduced oxTMB, resulting in a noticeable decolorization of the system. Based on this phenomenon, a novel colorimetric sensing platform was developed for quantitative detection of AA, with a linear range of 0.1–28 µM and a detection limit of 0.091 µM (3σ/m). Moreover, by employing AA as a mediator, the strategy was extended to alkaline phosphatase (ALP) detection, as ALP enzymatically hydrolyzes L-ascorbic acid-2-phosphate (AAP) to generate AA. The assay exhibited a linear response to ALP in the range of 0.2–6.5 U/L, with a detection limit of 0.12 U/L. The proposed sensor was successfully applied to the determination of AA and ALP in human serum samples. Furthermore, Co/Cu-MOF displayed strong antibacterial activity against both Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ), and its underlying antibacterial mechanism was elucidated. Collectively, this 2D bimetallic MOF provides a promising platform for biochemical sensing and antimicrobial technologies.