Van der Waals Layered Chiral Structure with Alkali Cation Exchange in LiInP₂S₆

In this study, we report the multiple synthesis routes and characterization of two-dimensional (2D) bimetallic thiophosphate, LiInP₂S₆, achieved through direct combination and P₂S₅ reactive flux methods. This material features a noncentrosymmetric space group (P312) and exhibits weak van der Waals forces between its layers. Differential thermal analysis indicated a congruent melting point of 785 °C. Structural characterization via single-crystal X-ray diffraction revealed detailed insights into its lattice configuration. Optoelectronic properties were assessed using UV-vis spectroscopy, showing a bandgap of 3.07 eV, and photoemission yield spectroscopy in air (PYSA), which determined a work function of 5.74 eV. Notably, despite the lithium ions being embedded and immobile within the layers rather than being loose in the interlayer space, the material exhibits significant alkali cation exchange capabilities. This happens by dislodging lithium ions from the intralayer space to the interlayer space and then exchanging them with incoming alkali ions. Experiments demonstrated interlayer expansion and significant ion exchange when exposed to Na⁺, K⁺, Rb⁺, and Cs⁺ ions, suggesting potential applications in ion exchange and encapsulation technologies. This work expands the compositional space for 2D layered thiophosphates, highlighting their promise for next-generation electronic devices and heavy metal remediation.(Figure presented).