Locations of Ca ²⁺ , Zn ²⁺ , and Sulfur in Zn-Modified LTA Zeolites During Sulfur Capture and Release

Hydrogen sulfide (H 2 S) is a toxic and corrosive contaminant in industrial gas streams, and its removal typically relies on single-use adsorbents that generate significant waste. Here, we report a regenerable zinc-modified Linde Type A (LTA) zeolite that captures sulfur from H 2 S at elevated temperature and can be repeatedly cycled without structural degradation. Zinc was incorporated into commercial Ca-LTA beads via ion exchange, yielding Zn-LTA materials that retain high surface area, crystallinity, and pore accessibility. Exposure to H 2 S at 400 °C resulted in rapid sulfur uptake (∼80 mg S g –1 ) with a near 1:1 Zn:S ratio, while heating in air at 600 °C removed ∼80% sulfur within 30 min. Characterization, including X-ray diffraction with Rietveld refinement, shows that Zn remains atomically dispersed as extra-framework Zn 2+ cations rather than forming ZnO. Structural analysis resolves the locations of Ca 2+, Zn 2+, and sulfur within LTA: Zn preferentially occupies six-membered ring faces and α- and β-cages, while sulfur binds near Zn within these cages. Upon regeneration, Zn retains its coordination environment, while ∼20% of sulfur remains associated with framework oxygen. These results establish Zn-LTA as a regenerable adsorbent–catalyst and provide structural insight into metal–zeolite interactions governing reversible sulfur capture.