A series of silver-based metal organic frameworks for colorimetric analysis of As(III) and S2-: Reaction mechanisms and applications for on-site analysis

Metal-organic frameworks (MOFs) are porous materials that constructed by various metal nodes and organic ligands, taking the advantages of high porosity, large specific surface areas and more reactive sites etc. However, the applications of MOFs in hydride generation (HG)/chemical vapor generation (CVG)-colorimetric systems are rare. Herein, a series of silver-based MOFs (Ag-MOFs) were synthesized and served as substrates for As(III) and S 2- colorimetric analysis. As(III) and S 2- were converted into its volatile species (AsH 3 and H 2 S) via HG and CVG process, respectively, providing merits of low matrix interferences (selectivity) and high vapor generation efficiency (sensitivity). Ag-MOF-3 exhibits the best performances for As(III) and S 2- analysis, its reaction mechanisms were further explored. Ag nanoparticles (redox reaction) and Ag 2 S nanoparticles (combination reaction) were formed after Ag-MOF-3 reacted with AsH 3 and H 2 S, respectively, leading to color change from light yellow to black. The variation was recognized by naked eye and smartphone. Standard cards/curves of visual method and smartphone RGB method were thus established for As(III) and S 2- . It is a potential analytical method for on-site and rapid analysis of As(III) and S 2- with merits of low-cost, easy-to-use and portability.