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

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) Å3, 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 (TiO2–xNx) under the same experimental conditions. This discovery enriches the categories of inorganic chalcohalides and provides more choices of candidate materials for photocatalytic applications.