Characterization And Exploration Of Catalytic Property Of Metal-Organic Coordination Polymers[Cd(C₆H₄O₂N)₂(H₂O)₄]∞

Porous metal-organic coordination polymers (MOCPs) are a novel type of functional materials with particular structures and properties dependent on their cavity sizes, shapes, and surface characteristics, which are controllable by selecting and assembling their building block molecules, i.e. various metal ions and organic ligands. They are attractive for their fascinating potential applications in catalysis, molecular recognition, gas adsorption, optics or magnetic materials, etc.In the paper, the multidentate carboxylic acid ligands were used to combine with Cd(Ⅱ), resulting in the three dimensional MOCPs single crystals—C12H16CdN2O8, with a low temperature hydrothermal synthesis method. The sample was characterized with IR spectra to affirm the organic groups in the frameworks, single-crystal X-ray diffraction to determine the crystal structure and composition of the frameworks, N2 adsorption isotherms at low temperature to measure the specific surface area and pore size distribution, and with TGA/DGA analysis to scale the thermal stability. Furthermore, the dissolution property and the photocatalytic activity of MOCPs under the ultraviolet ray condition were explored.The results indicated that the basic structural unit of MOCPs is Cd(C6H4O2N)2(H2O)4 , with Cd(Ⅱ) in the octahedron center which elongates slightly. Between structural units, hydroge bonds of O-H…O form, yielding an infinitely extensive three-dimensional supramolecular system; The synthesized MOCPs is heat stable and insoluble in acid, alkali and commonly used solvents. The MOCPs after being activated became a photo-catalyst, which could be used to catalyse the photo-decomposition of MB. The apparent activation energy is 17.2kJ/mol and the reaction rate is up to 156 s-1 at a temperature of 40℃and in a solution containing 5mg/L [Cd(C6H4O2N)2(H2O)4]∞(pH=8) under the irradiation of high-voltage mercury light.In addition, the author also analyse the structural causes for the photocatalytic activity of [Cd (C6H4O2N) 2 (H2O) 4]∞. The centre Cd (Ⅱ) is a six-coordination and there is a relatively large number of outer space orbit to occur electronic transitions. Cd(Ⅱ) coordinates with the water molecules in addition to nicotinic acid.And after appropriate activation and taking off water molecules, there are more unsaturated orbit, so the crystal is more prone to electronic transition.