Semirigid Tripodal Ligand Based Uranyl Coordination Polymer Isomers Featuring 2D Honeycomb Nets.

We report five novel uranyl coordination polymers, [(CH3)2NH2]UO2(BTPCA) (1), [(CH3)2NH2]UO2(BTPCA) (2), [(CH3)2NH2]2[UO2(BTPCA)][UO2(BTPCA)]·(H2O)5.5 (3), [(CH3)2NH2]2(UO2)2(BTPCA)2·(H2O)3 (4), and [(CH3)2NH2]UO2(BTPCA) (5), by the utilization of semirigid ligand 1,1',1″-(benzene-1,3,5-triyl)tripiperidine-4-carboxylic acid (H3BTPCA) and uranyl nitrate through solvothermal reactions. Single-crystal X-ray diffraction analysis reveals that the five compounds share a similar structure composition and local coordination mode to the exclusion of disordered water or DMF molecules. Each UO2(COO)3- motif is connected to six neighboring units through three BTPCA3- ligands, generating an infinite uranyl honeycomb (6, 3) net. The structures of all the five compounds consist of 2D honeycomb nets of various degrees of distortions, which are induced by the flexibility of piperidine rings. The dimethylamine cations and solvent molecules fill in the space between layers. Therefore, these five compounds are isomers in a broad sense. Notably, both compounds 3 and 4 possess 2-fold interpenetrated structures. For compound 5, the distance between the neighboring 2D honeycomb nets is 7.253 Å. This is the largest distance between the 2D honeycomb nets in uranyl-based coordination polymers, to the best of our knowledge. In addition, compounds 1, 2, and 4 are also characterized by infrared spectroscopy (IR), thermogravimetric analysis (TG), powder X-ray diffraction (PXRD), and luminescence properties.

[Preparation, spectral analysis and photocatalytic activities of TiO2 films codoped with iron and nitrogen].

Using tetrabutyl titanate as the titanium source, and ammonia and ferric nitrate as the sources of nitrogen and ferrum respectively, iron and nitrogen-codoped nano-TiO2 gelatins were prepared by sol-gel method. The iron and nitrogen-codoped nano-TiO2 complex films were prepared with the obtained gelatins used to coat the surface of cleaned glass slides by several times of dipping-lifting procedure, followed by natural seasoning at room temperature and calcined at 450 degrees C for 3 hours, then the films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectrum (XPS) and ultraviolet-visible diffuse reflectance spectrum (UV-Vis). The XRD spectra o f samples showed that the Fe-TiO(2-x)Nx, filmswere of anatase structure with a few of oxygen atoms in the lattice of anatase TiO2 substituted by nitrogen atoms, resulting in the distortion of crystal lattice. The SEM image showed that the nanoparticles of the films have a good dispersion characteristic and uniform orbicular shape with an average diameter of about 19 nm. The absorption edges of UV-Vis spectra exhibited a red shift up to 740 nm when the TiO2 films were codoped with iron and nitrogen. The XPS of the Fe-TiO(2-x)Nx film presented a lowering of Ti 2p(3/2) electron binding energy because of the codoping of iron and nitrogen, which then resulted in the widening of the absorption of visible light range. The photocatalytic properties were studied by photocatalytical degradation of sudan I as a model reaction in a self-assembled light-reactor. When the atomic ratio of Fe3+/Ti4+ reached 0.4%, the Fe-TiO(2-x)Nx film showed the highest catalytic performance in degradation of sudan I which was decomposed by up to 97% after 4 hours of photocatalytic reaction. Codoping of nitrogen and appropriate amount of iron in TiO2 enhances photoresponse and utilizing efficiency in visible light region, and then improves the performances of Fe-TiO(2-x)Nx photocatalyst. The complex film catalyst prepared by this method will have potential application in areas of wastewater disposal.