Polyoxometalate Derived Materials as Laccase‐Mimic Nanozyme and Reduction Catalyst for p‐Nitrophenol Remediation in Water

Abstract p‐Nitrophenol (PNP), a highly toxic water pollutant, poses significant risks to human health and the environment. For detecting PNP, a colorimetric method utilizing a nanozyme that mimics laccase activity presents a viable approach. In this study, PV₁₄@MIL‐88A, a robust nanozyme with superior laccase‐mimic capabilities, was synthesized by incorporating Na₇H₂[PV₁₄O₄₂] (PV₁₄) into MIL‐88A, a metal‐organic framework (MOF). This nanozyme demonstrates optimal laccase‐mimicking activity, enabling effective PNP detection via colorimetry and digital image colorimetry using smartphones. Theoretical analyses suggest that the outstanding laccase‐mimic activity of PV₁₄@MIL‐88A is derived from the optimized d‐band center in PV₁₄. Upon calcination with dicyandiamide (DCDA), PV₁₄@MIL‐88A transforms into Fe₂O₃/VO₂@NCNF. In the presence of NaBH₄, Fe₂O₃/VO₂@NCNF facilitates the conversion of PNP to p‐aminophenol (PAP), an essential precursor in paracetamol synthesis. The interaction between Fe₂O₃ and VO₂ in Fe₂O₃/VO₂@NCNF enhances adsorption and subsequent reduction of PNP. The saturation magnetization of Fe₂O₃/VO₂@NCNF reaches 25 emu g⁻¹, which supports efficient magnetic separation in the reduction process. This study not only advances an effective method for PNP detection but also facilitates its transformation from a hazardous pollutant into a valuable chemical precursor.