| Efficient removal of organic pollutants from wastewater has become a hot research topic due to its ecological and environmental importance. Traditional water treatment methods,like adsorption, chemical oxidation, and biological treatment, suffer from high operating costs, and even generate secondary pollutants. Photocatalysis via semiconductor photocatalysts, like Ti O2, Zn O, Fe2O3, Cd S, Ga P, and Zn S, has demonstrated high efficiency in degrading a wide range of organic pollutants into biodegradable or less toxic organic compounds, as well as inorganic CO2, H2 O, NO3-, PO43-, and halide ions. However, the difficult post-separation, easy agglomeration, and low solar energy conversion efficiency of these inorganic catalysts limit their large-scale applications. Exploitation of new catalysts has been attracting great attention in the related research communities. In the past two decades, a class of newly-developed inorganic–organic hybrid porous materials, namely metal–organic frameworks(MOFs) has generated rapid development due to their versatile applications, such as in catalysis and separation. Based on the photocatalytic degradation of organic pollutants, the theory of crystal engineering was applied to synthesize novel MOFs, and then MOFs were used as photocatalysis for the degradation of organic pollutants, the influence factors, kinetics, and pathway during the photocatalytic process was studied too.1. ZIF-8 [Zn(Me IM)2·2H2O](H-Me IM = 2-methylimidazole), a kind of MOFs which exhibits higher thermal and chemical stability than other MOFs, has attracted great interest as a promising candidate for sustainable energy and environmental remediation. Based on the photocatalytic degradation of organic pollutants, ZIF-8 was synthesized by electrochemical process in large scale, characterized by powder X-ray diffraction(PXRD), Fourier transform infrared spectra(FTIR), UV-Vis diffuse reflectance spectra(UV-vis DRS) and BET. Methylene blue(MB) was selected as degradation objective to test the photocatalytic performance of ZIF-8, and the influence factors, kinetics, and mechanism of photocatalytic MB degradation and stability of ZIF-8, were also studied. The results revealed that the ZIF-8 photocatalyst exhibited efficiently photocatalytic activity for MB degradation under UV irradiation, which was confirmed through the detection of hydroxyl radicals(·OH) by a fluorescence method. The MB degradation over the ZIF-8 photocatalyst followed a pseudo-first-order kinetics model. ZIF-8 worked effectively over a wide p H range from 6.0 to 12.0, and showed both high adsorption capacity and degradation efficiency for MB in a strong alkaline environment. The results indicated that ZIF-8 can be used as a highly efficient photocatalyst to decompose organic pollutants. Convenced by There was a lot of ?OH radicals produced in the photocatalytic process of ZIF-8, showing that ?OH radicals was the crucial activespecies for the photocatalytic degradation of MB. Based on the data of impact HD UHR-Q-TOF-MS analysis, the terminology of HOMO-LUMO gap was applied to describe the photocatalytic process of ZIF-8. What’s more, the smaller organic matters of MB decomposed by ZIF-8 can favor the biological treatment and the recycle of energy, as well as decrease the emission of greenhouse gas(CO2).2. A manganese- based metal – organic framework(Mn-MOF-1) was synthesized by hydrothermal methods Analysed by X-ray crystallography, phen acts as chelating ligand to join a Mn center, while the deprotonated Hbptc3- acts as bis-monodentate ligands to link two Mn centers into a zigzag Mn(phen)2(Hbptc) chain, then the adjacent Mn(phen)2(Hbptc) chains are further linked into three-dimensional framework with the aid of rich hydrogen-bonding interactions. Confirmed by the Kubelka–Munk function of UV-vis DRS the band gap Eg of Mn-MOF-1 was 3.3 e V. The data of Elemental analyses(EA) and FTIR showed that the sample was very pure. Then Mn-MOF-1 was used as photocatalyst to decompose methyl orange(MO) under UV light irradiation. When the concentration of MO was 10 mg/L, the p H was initial(5.7), and the dose of Mn-MOF-1 was 250 mg/L, Mn-MOF-1 exhibited the most excellent photocatalytic performance for decomposition of MO under UV light irradiation(the removal efficiency was 95% after 20 min). In the contrast tests, Mn-MOF-1 showed good photocatalytic activities which was close to commercial Ti O2(P-25). So Mn-MOF-1 can be used as a high efficient photocatalyst to decompose organic pollutants.3. A cadmium-based metal-organic framework(Cd-MOF-1) was synthesized via hydrothermal methods. Analysed by X-ray crystallography, [Cd(phen)3(H3bptc)2] consists of discrete cationic [Cd(phen)3]2+ and H3bptc- anion, forming 3D frameworks with the aid of hydrogen bonding and electrostatic interactions. The data of Elemental analyses(EA) and FTIR showed that the sample was very pure. Cd-MOF-1 is very stable under 250 ℃ tested by Thermogravimetric Analysis(TGA). Confirmed by the Kubelka–Munk function of UV-vis DRS the band gap Eg of Mn-MOF-1 was 3.4 e V. Phenol, a typical organic pollutant, was selected as degradation objective to test the photocatalytic performance of Cd-MOF-1, and the influence of initial concentration of phenol and the amount of Cd-MOF-1 were studied. The results also revealed that when the initial concentration of phenol was 50 mg/L, the doses of Cd-MOF-1 was 50 mg/200 m L, Cd-MOF-1 showed identical efficiency with Ti O2 under UV irradiation, indicating that Cd-MOF-1 can acts as a high efficient photocatalyst to decompose organic pollutants. |
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