Chemoenzymatic cascade conversion of methyl parathion to 4-aminophenol with immobilized organophosphate hydrolase onto Cu-MOF-loaded mesoporous silica

Abstract

Organophosphates (OPs), essential pesticide ingredients, are highly toxic and environmentally problematic. OPs can be efficiently hydrolyzed by the enzyme organophosphorus hydrolase (OPH). However, the resulting p-nitrophenol (4-NP) is still toxic, and its chemical reduction to p-aminophenol (4-AP) can be environmentally friendly and increase economic value. We constructed a chemical-enzymatic cascade catalyst system for methyl parathion (MP) using OPH and a copper-based metal-organic framework (HKUST-1) with 4-NP reduction catalytic activity. The nano-HKUST-1 was first loaded into aminated mesoporous silica nanospheres (MSN-NH2) to construct HKUST-1@MSN-NH2, and then OPH was immobilized into the HKUST-1@MSN-NH2 pores by a covalent method to obtain OPH@HKUST-1@MSN-NH2. The resulting composite catalyst, OPH@HKUST-1@MSN-NH2, achieved chemoenzymatic cascade catalysis of MP hydrolysis to 4-NP and subsequent reduction to 4-AP. The composite nano-biocatalyst has good catalytic performance and reusability, which can rapidly convert entirely 50 μM MP to 4-AP in 8 min at a dosage of 30 mM NaBH4. Still, it has 77% activity after 10 cycles and a stable material structure. The present study provides a strategy for constructing a chemoenzymatic cascade catalytic system, and the obtained composite nano catalysts achieve the continuous degradation and resourceful conversion of organophosphorus pollutants, which has specific practical application value.