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: {[Ag₆Cl₂(L₃)₅][BF₄]₄}_n(SCU-1) and [AgSCN(L₃)]_n(SCU-2). Single crystals were synthesized using the branched tube method, and X-ray crystallography revealed SCU-1’s large cationic framework with 193 atoms per unit cell and a volume of ∼10,000 ų, exhibiting 15.1% porosity. SCU-2, 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 SCU-1 and SCU-2 were investigated, revealing remarkable uptake capacities of 3.650 g/g and 3.749 g/g, respectively, setting a new benchmark for iodine removal. Additionally, the H₂S adsorption potential of these frameworks was explored for the first time. SCU-1, with BF₄^–and Cl^– as electron-rich sites, exhibited a higher H₂S adsorption energy (E_ads = −45.0 kJ mol^–1) compared to SCU-2 (E_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.