Breaking the conventional: Ligand-triggered Zn-MOF nanozyme with unusual oxidase activity for dual-channel sensing of benfuracarb

The activity of MOF-based nanozyme mainly relies on the metal sites, the development of organic ligands with intrinsic enzymatic-activity is of great significance for nanozyme-mediated sensors but it remains a huge challenge. Herein, the oxidase-like activity of an azo ligand, 4,4′-azodipyridine (AZPY), was first discovered by rational screening. A new Zn-MOF (JLU-MOF221) was successfully constructed based on the pillar-layered strategy to achieve well-isolated AZPY ligand and robust framework. JLU-MOF221 exhibited excellent affinity for 3,3′,5,5′-tetramethylbenzidine (TMB) (K_m: 0.180 mM; K_cat: 5.72 s⁻¹), as well as a rapid response time (60 s) and high storage stability (87 % activity over 8 months). The study revealed the unique four-electron O₂-to-H₂O reaction pathway without relying on active oxygen species. Moreover, combining the hydrolysis behavior of benfuracarb and nanozyme inhibition strategy, a colorimetry and fluorescent dual-channel sensor was firstly developed towards benfuracarb, reaching a low limit of detection of 130 ng/mL and 76 ng/mL, respectively. The breakthrough in enzyme activity of organic ligands not only provides an efficient alternative for the traditional assay to detect benfuracarb, but also greatly promotes nanozyme-mediated sensors to a new stage. © 2025 Elsevier B.V.