2-Aminoterephthalic acid co-coordinated Co-MOF fluorescent probe for highly selective detection of the organophosphorus pesticides with p-nitrophenyl group in water systems

It has drawn extensive research interest to integrate luminescent ligands into metal-organic frameworks as luminescent materials due to striking luminescent properties. In this work, a Co-MOF with weak fluorescence emission , [Co(OBA)(2,2′-BPY)], was synthesized by a mixed solvothermal route with Co(NO 3 ) 2 as the Co 2+ ion source, 4,4′-Oxybis(benzoic acid) (OBA) and 2,2′-Bipyridyl (2,2′-BPY) as the ligands. Its fluorescence was obviously enhanced through integrating a small amount of luminescent ligands: 2-aminoterephthalic acid. Interestingly, the above enhanced fluorescence could be selectively quenched by the organophosphorus pesticides with p-nitrophenyl group such as p-nitrophenyl phosphate (PNPP) and bis(p-nitrophenyl) phosphate (BNPP) in water systems. As a case, the detection limit towards PNPP was up to 352 nM (0.07 mg kg −1 ), which is far lower than the standards for similar pesticide residues in fruits in China (0.1–0.6 mg kg −1 ) [ 1 ]. At the same time, the above phenomenon of the fluorescence quenching was not interfered from some other pesticides, metallic ions, amino acids and aromatic nitrocompounds, implying the present fluorescent material has potential application as a highly selective probe for detecting PNPP pesticide residues in food and domestic water. Furthermore, a possible quenching mechanism was discussed.