NU-1000/Cu Nanocomposite-Immobilized Organophosphate Hydrolase for the Cascade Conversion of Methyl Parathion to 4-Aminophenol

Effective degradation and detoxification of the highly toxic organophosphate pesticide methyl parathion (MP) are important for pollution treatment and sustainable development. Enzymatic hydrolysis of MP by organophosphate hydrolase (OPH) is an effective way. However, hydrolytic product 4-nitrophenol (4-NP) remains environmentally hazardous. A promising strategy is to reduce 4-NP to 4-aminophenol (4-AP), which not only is weakly toxic but also has high application value. To realize the cascade conversion of MP to 4-AP with the dual objectives of detoxification and recycling, we designed a chemoenzymatic catalyst by immobilizing the OPH within a reduction-catalytic nanocomposite (NCu) constructed by generating copper nanoparticles (Cu NPs) in a zirconium-based metal-organic framework, NU-1000. Optimized OPH@NCu exhibited a 239% enhancement in catalytic activity compared to free OPH, attributed to substrate enrichment by NCu and activation of OPH by Cu²⁺. Moreover, OPH@NCu exhibited an average cascade conversion rate of 11.1 μmol min^-1 g_catalyst^-1, achieving a complete conversion of 50 μM MP to 4-AP within 9 min by using a low reductant concentration (15 mM NaBH₄). Notably, OPH@NCu demonstrated robust stability, retaining >86% of its activity after being stored for 10 days and nearly 80% of its activity over six reuse cycles. These results validate OPH@NCu as an efficient and sustainable platform for the cascaded detoxification and recycling of MP.