Two Water-Stable Silver–Sulfur MOFs with Interesting Topology: High-Performance H₂S Adsorption and Record-Breaking Iodine Uptake

Sulfur-based coordination polymers have gained significant attention, yet constructing 3D sulfur-based networks remains challenging. This study presents two novel 3D water-stable silver-sulfur MOFs: {<b>[Ag</b>_<b>6</b><b>Cl</b>_<b>2</b><b>(L</b>_<b>3</b><b>)</b>_<b>5</b><b>][BF</b>_<b>4</b><b>]</b>_<b>4</b><b>}</b>_{<b><i>n</i></b>}<b>(SCU-1)</b> and <b>[AgSCN(L</b>_<b>3</b><b>)]</b>_{<b><i>n</i></b>}<b>(SCU-2)</b>. Single crystals were synthesized using the branched tube method, and X-ray crystallography revealed <b>SCU-1's</b> large cationic framework with 193 atoms per unit cell and a volume of ∼10,000 ų, exhibiting 15.1% porosity. <b>SCU-2</b>, with a simpler structure, showed 5.9% porosity. Leveraging the strong silver-sulfur affinity and the methimazole-based ligands' potential for iodine uptake, the iodine adsorption capabilities of <b>SCU-1</b> and <b>SCU-2</b> were investigated, revealing remarkable uptake capacities of <b>3.650 g/g</b> and <b>3.749 g/g</b>, respectively, setting a new benchmark for iodine removal. Additionally, the H₂S adsorption potential of these frameworks was explored for the first time. <b>SCU-1</b>, with BF₄^-and Cl^- as electron-rich sites, exhibited a higher H₂S adsorption energy (<i>E</i>_ads = -45.0 kJ mol^-1) compared to <b>SCU-2</b> (<i>E</i>_ads = -39.0 kJ mol^-1), where thiocyanate serves as the electron-rich component. Simulations aligned well with experimental data, highlighting the frameworks' potential for gas adsorption applications. This work advances the design of sulfur-based MOFs for environmental remediation, particularly in iodine and H₂S capture.