Barium-Based Coordination Polymer with Coupled Photochromism and Long Afterglow Luminescence for High-End Anticounterfeiting

Abstract Stimuli-responsive materials featuring multiple photophysical functionalities have garnered immense attention for advanced applications. Herein, a barium-based CP (CP-SW5) is rationally designed and synthesized by assembling a conjugated N,O-heterocyclic ligand (HL) with Ba(NO3)2. Single-crystal X-ray diffraction reveals that CP-SW5 forms a rigid two-dimensional supramolecular architecture via Ba‒O coordination, which is assembled into a three-dimensional framework through interlayer hydrogen bonding interactions. This robust structure suppresses the nonradiative decay of triplet excitons and enhances spin–orbit coupling. Characterizations verify its tunable cyan-to-yellow LAL emission, yellow-to-gray photochromism under UV irradiation, and effective phosphorescence-to-photothermal conversion. DFT calculations and experiments confirm that photoinduced electron transfer from the electron-rich terminal to the electron-deficient core group generates HL• radicals, which not only trigger photochromism but also enhance self-absorption to boost photothermal conversion efficiency. This work provides a feasible strategy for constructing multifunctional CPs with integrated photofunctional properties, showing tremendous potential in intelligent anticounterfeiting and information security applications.