Selective Adsorption And Photocatalytic Performance Of UiO-66-NH₂ And Its Composites

K2Ti4O9 and N doped K2Ti4O9 (entitled "N-K2Ti4O9") were both prepared by high temperature calcining. And N-K2Ti4O9/UiO-66-NH2 composite was synthesized via self-assembly route. Then the pure materials and the composites were systematically characterized, and their adsorption and photocatalysis performance were studied. This dissertation is composed of two parts.(1) Herein, two zirconium(IV)-based MOFs UiO-66 and UiO-66-NH2 had been successfully prepared by a facile solvothermal method, and were characterized by X-ray diffraction (XRD), field emission transmission electron microscopy (FETEM), N2 adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS) and zeta potential. They exhibit small size, large surface area, and can remove cationic dyes from aqueous solution more effectively than anionic dyes. This adsorption selectivity is due to the favorable electrostatic interactions between the adsorbents and cationic dyes. Furthermore, owing to the individual micropore and mesoporous structures of UiO-66-NH2 and its more negative zeta potential resulted from the charge balance for the protonation of -NH2, UiO-66-NH2 displays much higher adsorption capacity for cationic dyes and lower adsorption capacity for anionic dyes than UiO-66.(2) We had successfully synthesized N-K2Ti4O9/UiO-66-NH2 composites by a facile solvothermal method, and they exhibit a hierarchical core-shell structure with UiO-66-NH2 forming the shell around the N-K2Ti4O9 core. Photocatalytic activities of N-K2Ti4O9/UiO-66-NH2 composites were investigated by the degradation of various dyes under visible light irradiation. The results show that N-K2Ti4O9/UiO-66-NH2 composites exhibit higher photocatalytic activity as compared with the pure materials, and this is due to the high adsorption capacity of UiO-66-NH2 and the compounding induced higher separation efficiency of photogenerated electron-hole pairs. In particular, when the mass ratio of N-K2Ti4O9 to ZrCl4 is 3:7, the composite exhibits the highest photocatalytic activity. In addition, owing to the fact that the positively charged groups of cationic dyes undergo electrostatic attraction with the negatively charged backbone of UiO-66-NH2, the degradation of cationic dyes is much more effective than that of anionic dyes.