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Although phase transition materials (PTMs) under external stimuli are of great research interest duo to their rich potential applications, it is still challenging to explore multi‐responsive PTMs. Herein, two different phases of organic–inorganic hybrid copper‐based halides, α‐ and β‐Gua3Cu2I5 (Gua+=CN3H6+), were synthesized by solvent evaporation method, which they crystalize in the noncentrosymmetric space group Fdd2 with zero‐dimensional structure and centrosymmetric space group C2/c with one‐dimensional metal‐halogen framework, respectively. Interestingly, it is firstly demonstrated that Gua3Cu2I5 simultaneously possesses reversible PL conversion and NLO switching properties in response to thermal stimulus. Strikingly, apart from heat, its structural phase transition can also be triggered by crystalline‐phase‐recognition (CPR) and mechanical force. These new findings may pave a path for future exploration of PTMs with multiple physical properties. [ABSTRACT FROM AUTHOR]

Metal chalcogenophosphates are receiving increasing interest, specifically as promising infrared nonlinear optical (NLO) candidates. Here, a rare‐earth chalcogenophosphate Eu2P2S6 crystallizing in the monoclinic noncentrosymmetric space group Pn was synthesized using a high‐temperature solid‐state method. Its structure features isolated [P2S6]4− dimer, and two types of EuS8 bicapped triangular prisms. Eu2P2S6 exhibits a phase‐matchable second‐harmonic generation (SHG) response ≈0.9×AgGaS2@2.1 μm, and high laser‐induced damage threshold of 3.4×AgGaS2, representing the first rare‐earth NLO chalcogenophosphate. The theoretical calculation result suggests that the SHG response is ascribed to the synergetic contribution of [P2S6]4− dimers and EuS8 bicapped triangular prisms. This work provides not only a promising high‐performance infrared NLO material, but also opens the avenue for exploring rare‐earth chalcogenophosphates as potential IR NLO materials. [ABSTRACT FROM AUTHOR]