Weaving Gallium-Sulfide Clusters with Antimony Bridges into an Open-Framework for Ni2+ Adsorption

The efficient removal of Ni2+ from radioactive wastewater is crucial for environmental protection and nuclear safety, yet current ion exchangers often exhibit limited stability and selectivity. Herein, we report an open-framework gallium–antimony sulfide, K3.6[NH4]0.1[CH3NH3]0.3Ga4SbS9SH·0.9H2O (GaSbS-2K), constructed from supertetrahedral T2-{Ga4S9SH} clusters and asymmetric Sb bridges. Its three-dimensional framework features intersecting chiral channels and tetrahedral voids that facilitate ion diffusion and exchange. GaSbS-2K exhibits rapid Ni2+ adsorption, achieving 67.66% uptake within 2 min and 97.54% removal at equilibrium, with a pseudo-second-order rate constant of 0.318 g mg–1 min–1. The material shows a maximum adsorption capacity of 90.78 ± 2.74 mg g–1 under neutral conditions and remains stable across a wide pH range (3–12). It retains strong selectivity for Ni2+ in the presence of competing ions, maintaining >72% removal even in seawater. The rapid adsorption kinetics enable continuous-flow applications in both fixed-bed columns and composite membranes, achieving >99% removal of Ni2+. Notably, the GaSbS-2K/PTFE membrane with an 80 μm active layer completely removes Ni2+ from 1000 mL of solution at a flux of 1.91 mL min–1 cm–2 with only 0.25 s of contact time. Combined with its facile synthesis, radiation stability, and regenerability, GaSbS-2K represents a promising adsorbent for radionuclide-contaminated wastewater treatment.