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

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.