Stimuli‐Responsive Cd(II) Coordination Polymer Based on Viologen Exhibiting Photochromism, Photocontrolled Fluorescence, Ammonia Vapor Sensing, and Anti‐Counterfeiting

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Abstract

Abstract Photochromic materials containing viologen have shown broad practical applications, but synthesizing multifunctional photochromic materials remains a significant challenge. In this work, a novel Cd(II) coordination polymer, {[Cd 4 (BCMBPY) 2 (BTEC) 2 ]·4H 2 O} n ( 1 ), has been successfully synthesized under solvothermal conditions based on viologen ligand 1,1′‐bis [(2‐carboxybipheny‐4‐yl)methyl]‐4,4′‐bipyridinium dichloride (H 2 BCMBPY·2Cl), 1,2,4,5‐benzenetetracarboxylic acid (H 4 BTEC), and Cd(NO 3 ) 2 ·4H 2 O. Single crystal X‐ray diffraction analysis reveals that Cd(II) ions connect BCMBPY and BTEC 4‐ anions to form two‐dimensional (2D) layered structure in 1 . Upon exposure to a 300 W Xe lamp, 1 transitions from beige to light green rapidly within 15 s and exhibits photocontrolled fluorescence with the increasing irradiation time. The discoloration mechanism of coordination polymer 1 was investigated via time‐dependent density functional theory (TDDFT). Additionally, 1 can detect ammonia vapor, changing from beige to dark green upon exposure. Furthermore, 1 has potential application ability in anti‐counterfeiting.