A UV and X-ray dual photochromic Zn (II) metal-organic framework based on viologen: Photo-controlled luminescence and temperature-dependent phosphorescence

Nowadays, photoactive viologen units have been widely encapsulated in metal-organic frameworks and assembled into multifunctional materials with photochromism and other light regulating properties. A novel host-guest MOF material, {[Zn(bcbpy)0.5(IPA)]·CH3CN}n (1), has been constructed by a viologen ligand 1,1′-bis((3-carboxylatobenzyl)-4,4′-bipyridinium)-dichloride (H2bcbpy·2Cl), isophthalic acid (IPA) and zinc(II) chloride. Complex 1 exhibits UV and X-ray dual photochromism and photo-controlled luminescence properties. Complex 1 also exhibits a temperature-dependent phosphorescence from cyan to yellow when the temperature increases from 77 to 297 K. 1T will be obtained when 1 is heated in air at 230 °C for 30 min, 1T shows less sensitive photochromic property than 1 due to its longer C–H⋯O hydrogen bond distance for electron transfer pathway. In addition, complex 1 has the potential application as an inkless and erasable printing material due to the excellent photochromic property.