Cation‐Directed Solvent Inclusion in Zero‐Dimensional Indium Halides for Tunable and Stimuli‐Responsive Emission

ABSTRACT Solvent molecules incorporated within the crystal lattice of zero‐dimensional (0D) metal halides play an important role in determining their structure and optical properties. However, achieving predictable control over solvent inclusion remains a significant challenge. Herein, we report five 0D indium halides, (TMPA) 2 InCl 5 , (Ch) 2 InCl 5 ·DMF (1·DMF), (Ch) 2 InCl 5 ·2H 2 O·MeOH (1·2H 2 O·MeOH), (Ch) 2 InCl 5 ·H 2 O·EtOH (1·H 2 O·EtOH) and (Ch) 2 InCl 5 ·H 2 O (1·H 2 O), synthesized using two structurally analogous organic cations: Ch + (choline), containing hydrogen‐bonding functional groups (―OH), and TMPA + (trimethylpropylammonium) lacking hydrogen‐bonding groups. Structural analysis reveals that the organic cation with an ―OH group can facilitate the incorporation of solvent molecules into the crystal lattice of 0D indium halides. These host materials are non‐emissive, whereas Sb 3+ doping activates broadband self‐trapped exciton (STE) emission. Among them, 1·2H 2 O·MeOH:Sb exhibits a single yellow STE emission band peaking at 603 nm, while 1·H 2 O·EtOH:Sb, 1·H 2 O:Sb and 1·DMF:Sb display excitation‐dependent dual emission bands, consisting of a high‐energy one in the 400–550 nm region and a low‐energy band centered at 645, 660, and 675 nm, respectively. Excitingly, reversible transformation between yellow‐emitting 1·2H 2 O·MeOH:Sb and orange‐red‐emitting 1·H 2 O:Sb can be induced through heating‐cooling treatment and MeOH/H 2 O stimuli. This work provides new insights into the rational design of stimuli‐responsive 0D metal halide luminescent materials.