Zinc(II)-Organic Framework Films with Thermochromic and Solvatochromic Applications

Abstract

Multiple-stimuli-responsive photoluminescence films based on a Zn-II-organic framework, {[Zn-2(Htpim)(3,4-pydc)(2)].4 DMF.4 H2O}(n) (1, Htpim=2,4,5-tri(4-pyridyl)imidazole, 3,4-H(2)pydc=3,4-pyridinedicarboxylic acid), were fabricated. This compound consisted of a 2D corrugated layer, {Zn(3,4-pydc)}(n), which was further pillared using a Y-shaped pillar N-donor ligand (Htpim) to form a 3D-pillared-layer framework with 1D open channels. The rectangular channels in the as-synthesized compound are fully occupied by guest DMF and H2O molecules. The framework exhibits instant and reversible thermochromic properties corresponding to the removal of different H2O and DMF guest molecules as temperature increases. The pale-yellow crystal undergoes significant redshifting to a greenish emission centered at 530 nm. Compound 1 also showed remarkable solvatochromic effects in the presence of various organic solvents without affecting its structural integrity. In addition, polycrystalline MOF films were grown on an alpha-Al2O3 support for switchable and fast-response thermochromic and solvatochromic sensors.