Design of bifunctional ultrathin MnO2 nanofilm with laccase-like activity for sensing environmental pollutants containing phenol groups

Laccase-catalyzed oxidative reactions are increasingly examined as a reliable approach to environmental analysis and remediation, and it is urgent to widen metal category to compensate huge gap in the number of studies on copper- and non-copper laccase mimics. Herein, two-dimensional ultrathin MnO2 nanofilm (Mn-uNF) was designed via a chemical deposition and alkali etching process. Similar to Cu-laccase, Mn-uNF can oxidize phenols via a one-electron-transfer reaction of Mn(III) and accelerate the MnIII/MnIV state cycle through an unconventional oxygen reduction process. The excellent laccase-like performance of Mn-uNF can be ascribed to the abundant atomically dispersed Vo-assisted Mn(III) and surface -OH species, which was confirmed by characterizations and DFT calculation. Further, a facile dual-function colorimetric platform was designed for array sensing of o-, m-, and p-dihydroxybenzene isomers and one-step discrimination of tetracyclines containing phenol groups. These findings provide reasonable guidance for the design of a nanozyme with active Mn sites as a new family member of highly efficient copper-free laccase mimics. Laccase-catalyzed oxidative reactions are increasingly examined as an alternative approach to environmental analysis and remediation. In this study, we explored an ultrathin Mn-uNF as a new family member of highly efficient copper-free laccase mimics. Based on the laccase chromogenic mechanism, a facile sensor equipped with Mn-uNF was designed for selective recognition of o-, m-, and p-dihydroxybenzene isomers, as well as one-step recognition of TC, OTC, and CTC among various antibiotics, as shown here. This study reveals the great application potential in environmental analysis, which will also inspire the design of Mn-based laccase-like nanomaterials.