Quaternary Chalcohalides CdSnSX₂ (X = Cl or Br) with Neutral Layers: Syntheses, Structures, and Photocatalytic...

Inorganic chalcohalides are attracting a tremendous amount of attention because of their remarkable structural variety and desirable physical properties. Although great advances have been made in recent years, functional inorganic chalcohalides with two-dimensional neutral layers are still rare. Herein, two novel chalcohalides CdSnSX₂ (X = Cl or Br) with high yields were obtained by reacting CdX₂ with SnS using a traditional solid-state method at 823 K. Both of these chalcohalides adopt orthorhombic space group Cmcm (No. 63) with the following structural values: a = 4.014(4)-4.064(2) Å, b = 12.996(2)-13.746(3) Å, c = 9.471(2)-9.621(2) Å, V = 494.1(8)-537.5(2) ų, and Z = 4. The prominent architectural feature is the unique two-dimensional [CdSnSX₂] neutral layer consisting of composite [CdX₂] and [SnS] sublattices that are connected alternately through the Cd-S-Sn bonds along the ac plane. The [CdX₂] sublattice consists of a single octahedral chain of Cd-centered [CdX₄S₂] groups sharing cis-X edges, while the [SnS] sublattice consists of a bend-shaped chain of unusual [SnS₂X₂] units sharing vertices of S atoms. Significantly, each CdSnSX₂ form (X = Cl or Br) shows high visible-light-induced photocatalytic activity for rhodamine B degradation, which is ∼7.0 times higher than that of nitrogen-doped TiO₂ (TiO_2-N) under the same experimental conditions. This discovery enriches the categories of inorganic chalcohalides and provides more choices of candidate materials for photocatalytic applications.