Thiostannate coordination transformation-induced self-crosslinking chalcogenide aerogel with local coordination control and effective Cs+ remediation functionality

Abstract

Thiostannate ammonium chalcogenide aerogel (TAC) is synthesized through a unique self-crosslinking polymerization reaction between tetrahedral thiostannate dimer clusters ([Sn₂S₆]⁴⁻) and various ammonium ligands (NR₄⁺). TAC is a unique and rare chalcogenide aerogel (so called “chalcogel”) stabilized without using a cationic transition metal center. In-depth and synergistic structural analyses reveal that after the self-condensation reaction, the thiostannate clusters are stabilized into a three-dimensional solid network with the support of an ammonium spacer. Consequently, thiostannate coordination is successfully transformed from tetrahedral to a distorted trigonal bipyramidal geometry, yielding a [Sn₃S₇]²⁻ cluster-based porous chalcogenide network. This organic/inorganic heterostructure has a large specific surface area (158–363 m² g⁻¹), macroscopically random orientation of pores, soft basicity, controllable hosting ammonium ligand, and rapid mass transport through multiscale channels. These characteristics enable remarkable radionuclide control functionality such as large Cs⁺ adsorption capacity (141–220 mg g⁻¹), high selectivity towards cations with intermediate chemical hardness (e.g., Cs⁺), structural integrity over a wide pH range (2–8), and rapid ion uptake (50% in 30 min and complete equilibrium within 3 h). This study demonstrates that the self-crosslinking mechanism of chalcometallate clusters can be utilized as a diverse platform to synthesize a broad range of chalcogenide heterostructures with desirable functionalities.