Toward on-site analysis: a paper-based luminescent metal organic framework sensing strategy for sulfide via chemical...

The sulfide ion (S^2-) is one of the toxic pollutants in water systems and its concentration is a critical environmental index. Traditional methods for S^2- detection are typically confined to laboratory analysis, limiting their applicability for on-site monitoring. Therefore, a chemical vapor generation (CVG)-smartphone colorimetric method was established for S^2- on-site detection. S^2- was converted into volatile H₂S through the CVG process, enabling efficient sample introduction while minimizing interference from complex matrices. The generated H₂S reacts with Ag-metal-organic framework (Ag-BDC)-immobilized test paper, forming Ag₂S on its surface and resulting in gradual fluorescence quenching, thereby allowing quantitative detection of S^2-. The method was successfully applied to the analysis of S^2- in four real water samples, three condiments and one certified reference water sample, achieving satisfactory recoveries ranging from 98 to 108%. By integrating the advantages of CVG (e.g., high sample introduction efficiency and reduced matrix interference) with those of colorimetry (e.g., operational simplicity and low cost), this approach demonstrates promising potential for rapid and on-site analysis.