Dual enzyme-mimicking active metal-organic frameworks material with strong adsorption and degradation functions for methyl blue

Nanozymes have emerged as promising alternatives to natural enzymes owing to their high stability, cost-effectiveness, and catalytic versatility. In this work, the Ce-TPA metal-organic frameworks (MOF) material with dual enzyme activities of oxidase (OXD) and peroxidase (POD) was constructed through a bottom-up approach using the coordination reaction between Ce ions and terephthalic acid (TPA) molecules. The formation of MOF structure not only displays high water adsorption capacity but also enhances the thermal stability of TPA organic ligands, which also lays the foundation for the reuse of Ce-TPA materials. Therefore, the Ce-TPA MOF materials can produce high adsorption capacity for methyl blue (MB) through electrostatic attraction and hydrogen bonds, and this adsorption process follows the pseudo-second-order and intraparticle diffusion model. We also compared the effects of synchronous and asynchronous removal of MB, and the results confirmed that combining the pre-adsorption process with enzymatic degradation can enhance the removal efficiency of MB, with an efficiency exceeding 95 %. Additionally, steady-state enzymatic kinetics demonstrated that the Ce-TPA MOF materials has a high affinity for the MB substrate, following the Michaelis-Menten behavior, and the generated superoxide anions (O 2 •− ) and hydroxyl radicals (•OH) are the main reasons for the oxidation and degradation of MB dyes.