Dual-Template-Directed\nZero-Dimensional Bismuth Chlorides:\nStructures, Luminescence, Photoinduced Chromism, and Enhanced Proton\nConductivity

Zero-dimensional (0D) hybrid organic–inorganic\nbismuth halides\nhave attracted immense scientific interest as promising candidates\nfor lead-free materials. Here, by using a typical solvothermal method,\ntwo mixed-cation-phase 0D hybrid bismuth chlorides of [HPDA][H<sub>2</sub>PDA]BiCl<sub>6</sub> (<b>1</b>) and [Hbzim][H<sub>2</sub>PA]BiCl<sub>6</sub> (<b>2</b>) (PDA = bis(4-pyridyl)amine,\nbzim = benzimidazole, PA = 2-picolylamine) have been assembled based\non a series of organic amine guests. Both compounds exhibit interesting\nphotoluminescence phenomena, in which compound <b>1</b> exhibits\na double emission property of blue fluorescence and yellow-green phosphorescence\nsimultaneously, while compound <b>2</b> exhibits wide-band yellow-green\nemission under visible light excitation. The luminescence mechanism\nis explained by experiments and theoretical calculations. In view\nof the fact that halometallate units and the conjugated nitrogen heterocyclic\nsystems can act as electron donors and electron acceptors, respectively,\nboth compounds exhibit free radical-driven photochromism induced by\nelectron transfer under xenon lamp irradiation at room temperature.\nIn addition, benefiting from abundant hydrogen bond networks in structures,\nthe two compounds show significant temperature-dependent proton conduction\nbehavior in the range of 298–343 K, and the proton conductivity\nof both compounds is significantly improved after light irradiation.\nOur study demonstrates two novel hybrid mixed-cation-phase 0D hybrid\nbismuth halides with photoluminescence, photochromism, and photomodulated\nproton conduction properties, which enriches the dual-template-directed\nmetal halide system and provides a feasible scheme for the synthesis\nof photoresponsive smart materials.