Cobalt(II) and Cadmium(II) Metal-Organic Framework with Benzene-1,3,5-tricarboxylate and Viologen Guest: Stimuli-Responsive Photochromism, Volatile Amine Detection, and Hydrogen Generation.

Two Co(II) and Cd(II) coordination polymers, {(Me2bipy)[Co5(btc)3(Hbtc)(OH)]·2DMF·9H2O} n (CoMOF) and {(Me2bipy)[Cd2(μ4-btc)2]} n (OGU-2), were synthesized and characterized using IR spectroscopy, elemental analysis, and powder and single-crystal X-ray diffraction techniques. The Cd1 ion is seven-coordinated, adopting a distorted monocapped trigonal prismatic geometry (CdO7). OGU-2 exhibits a 3D porous framework with a rare flu-3,6-C2/c topology. The framework contains one-dimensional channels along the c axis with dimensions of approximately 10 × 10 Å2. The photochromic behavior of OGU-2 was investigated, revealing excellent chromic properties in response to multiple external stimuli, including UV light, temperature, and organic amines. CoMOF, a coordination polymer reported previously, along with OGU-2, was evaluated as a catalyst for hydrogen gas production via the methanolysis reaction of NaBH4. The results demonstrated that these coordination polymers exhibited high catalytic activity for hydrogen production, comparable to the high values reported in the literature.