In Situ Ligand-Transformation-Assisted Assembly of a Polyoxometalate and Silver-Phosphine Oxide Cluster for Colorimetric Detection of Phenol Contaminants

Abstract

In situ ligand transformation strategies represent an efficient pathway for constructing function-oriented polyoxometalate (POM)-based crystalline materials. Herein, three POM-based hybrid networks were synthesized through in situ transformation of the phosphine ligand, formulated as [Ag(dppeo)₆][H₂PMo₁₂O₄₀]·5H₂O (1), [Ag(dedpo)]₄[SiW₁₂O₄₀]·6H₂O (2), and [Ag(dppeo)]₃[PW₁₂O₄₀]·3H₂O (3) (dedpo = (2-(diphenylphosphaneyl)ethyl)diphenylphosphine oxide; dppeo = ethane-1,2-diylbis(diphenylphosphine oxide)). During the synthesis of these compounds, the 1,2-diphenylphosphine ethane molecule underwent in situ oxidation, transforming into dppeo and dedpo ligands, respectively. Compound 1 features a supramolecular architecture assembled from [Ag(dppeo)₃]⁺/[Ag₂(dppeo)₆]²⁺ cationic clusters with disordered Ag centers and protonated [H₂PMo₁₂O₄₀]^- anions. Compound 2 presents a 3-D POM-supported metal-organic framework consisting of binuclear [Ag(dedpo)]₂²⁺ units, {-dedpo-Ag-dedpo-} chains, and [SiW₁₂O₄₀]^4- polyoxoanions. Compound 3 displays a 2-D layered structure formed by {-dppeo-Ag₃-dppeo-} chains and [PW₁₂O₄₀]^3- clusters. Pronounced argentophilic interactions are observed in compounds 1 and 3. The three compounds demonstrate satisfactory heterogeneous catalytic activity in the colorimetric detection reactions toward phenol pollutants with detection limits of 1.73, 1.92, and 4.6 μM, respectively. Additionally, compounds 1-3 show high anti-interference capabilities and high sensitivity in differentiating phenol from its halogenated derivatives. This work presents some guidance for designing specific function-oriented POM-based materials via an in situ ligand transformation strategy.