A Multistimuli-Responsive Cd-MOF Constructed by an Extended Viologen-Based Carboxylate Ligand

Multistimuli-responsive crystalline materials have a wide range of application prospects. However, development of new multistimuli-responsive materials remains full of challenge. In this work, taking a symmetrical modified extended viologen (ExV)-based carboxylate 1,1-bis(4-carboxybenzyl)-2,5-bipyridyl thiophene dichloride (H2L·Cl2) as a ligand and terephthalic acid (PTA) as an auxiliary ligand, a multistimuli-responsive crystalline 3D MOF material {[Cd2(L)(PTA)2]·3H2O}n (Cd-MOF-1) was constructed successfully. Cd-MOF-1 shows distinctive photochromic and electrochromic properties, which can be attributed to the formation of viologen radicals induced by electron transfer (ET) under external photo/electricity stimuli. Furthermore, the title compound also displays photomodulable fluorescence and sensitive and distinguishable color response to propylamine (PA) vapor relative to other amine molecules. The distinguishable selectivity toward volatile amine vapors may be caused by the differences in the size or electron propelling capacity of the amines. In addition, the photochromic character of the title compound makes it suitable for ink-free erasable printing. This excellent multistimuli-responsive material may have more potential application values in the areas of photoelectric devices, light printing, volatile amine detection, etc. It is also helpful for us to further explore and develop MOF-based multistimuli responsive materials constructed by ExV derivatives.