3D supramolecular framework based on mixed anions of polyoxometalate and carboxylate: catalytic synthesis of quinones, intelligent detection and deep recognition of phenols

In this work, a new compound [Cu2(L)(HL)2(TeMo6O24)(ox)]·(H2L)·2(H2O) (1) was synthesized by introducing two anions, [TeMo6O24]6– and oxalate (ox2–), as well as two cations, the copper ion Cu2+ and the protonated N,N′-bis (3-methylpyridine) naphthalene-2,6-dicarboxylamide (H2L2+). In compound 1, the metal-organic chain constructed by [TeMo6O24]6−, oxalate, and Cu2+ forms a two-dimensional coordination network through two amide ligands with different coordination modes and eventually expands into a three-dimensional supramolecular framework. Compound 1 was used as a peroxidase-like substance to study its colorimetric detection performance for seven phenolic compounds, and the corresponding limit of detection (LOD) ranged from 7.24 to 44.8 nM. A colorimetric sensing array was constructed by principal component analysis to explore the accurate differentiation of five structurally correlated phenolic compounds. Taking 2,3,6-trimethylphenol as the representative research object, a smartphone-assisted portable detection strategy was established, with a LOD of 390 nM. Compound 1 was used as a heterogeneous catalyst to study the synthesis of corresponding quinones by the oxidation of phenols, which demonstrated good conversion rates and selectivity. The stability of the material and the catalytic oxidation mechanism have also been studied.