Metal organic frameworks (MOFs) have shown promising adsorptive desulfurization (ADS) capacity yet remains great challenges to maintain excellent performance in presence of water. Guided by the density function theoretical (DFT) calculations, we select bromine modified linkers with different substitution degrees to construct MIL-47-xBr to regulate the porosity and hydrophobicity. The optimized MIL-47-Br exhibits the highest saturation dibenzothiophene (DBT) capacity of 179.2 mgS g −1 from the hydrous oil, surpassing the record of all ADS adsorbents. Meanwhile, the excellent selectivity, adsorption kinetics, and recycle stability endow MIL-47-Br with superior ADS performance from the commercial hydrous gasoline. With the DBT capacity decreases by only 12.3% from the commercial gasoline, a continue flow ADS is successfully achieved on the fixed-bed of MIL-47-Br column. Therefore, this facial strategy of simple substitution can fully exploit the functions of open metal sites for enhancing the task-specific selectivity, and has a promising application prospect in industrial ADS.
The cycloketones were prepared efficiently via the selectively hydrogenation of aqueous phase lignin-derived single phenolic monomer and mixtures. The yield and selectivity of cycloketones was greatly improved over Br modified metal-acid mixed catalyst (PdH5@Br). First, the effect of side-chain functional structures on the aqueous-phase hydrogenation of phenols with Pd/C catalysis was investigated and it was found that the benzene ring with methyl group attached is more easily hydrogenated, and the phenolic hydroxyl side chain was more susceptible to form carbonyl than methoxy groups. A large number of enols existed, thus the catalyst acidity was adjusted by extra addition of HZSM-5, over which the yield of cycloketones from guaiacol was significantly boosted to 67.9%. Subsequently, the electronic properties of catalyst were altered by adding Br over Pd catalyst, weakening the over-chemisorption of intermediate phenol, and the hydrogenating of phenol under PdH5 were enhanced, thus an increased yield of cycloketone of 18.4% occurred. After the hydrotreating of guiaiacol for 2 h at 523 K and 2 MPa H 2 , the yield of cycloketone reached 80.4% on PdH5@Br. The hydrotreating performance of PdH5@Br with lignin-derived phenolic monomer mixtures as the feedstock was also tested, and it presented great universality and stability. It provides an efficient catalyst system and promising technological ideas for biomass hydrotreating.
Solar-driven photodegradation technology is a highly promising route for resolving environmental pollutants. However, the performance of photocatalysts is usually limited by the poor light harvesting, the high recombination of photogenerated electron-hole pairs, and the insufficient surface active sites. In this work, thin Bi 2 O 2 (OH)(NO 3 ) nanosheets co-modified with oxygen vacancies and bromine-grafting (BNSBr-OV) presented a superb rhodamine B photodegradation efficiency of 98.5 % within 4 h under visible light (λ＞420 nm), which was 8.2 times higher than that of pristine Bi 2 O 2 (OH)(NO 3 ). Besides, BNSBr-OV exhibited universal photocatalytic abilities of degrading various antibiotics, including tetracycline hydrochloride, ofloxacin and sodium sulfacetamide. The introduction of oxygen-vacancy and grafted bromine dual active sites can not only improve the light harvesting ability of the photocatalyst, but also promote the migration efficiency of photogenerated carriers, which boosts its photocatalysis performance. This study provides a platform for understanding the dual active sites modified single-crystal material, which potentially offers new design of environmental catalysts for multiple applications.
Shiyu He,Aijia Wei,Wen Li,Xue Bai,Lihui Zhang,Xiaohui Li,Rui He,Lili Yang,Zhenfa Liu
The Br − modified LiNi 0.815 Co 0.15 Al 0.035 O 2 (NCA) cathode materials areprepared via a situ doping method for the first time. The structural and electrochemical properties within Br − modified NCA cathode material are in an in-depth analysis. X-ray diffraction (XRD) results show enlarged interslab spacing due to the fact that partial Br − has doped into the bulk particles of NCA to replace O 2− in 6c site. Density functional theory (DFT) calculations suggest that Br − doping mainly occurs in the surface layer. Moreover, the Br ‒ modified NCA cathode materials present smaller primary particles than pure NCA, which is proved by calculations of particle size from random scanning electron microscopy (SEM) images. X-ray photoelectron spectroscopy (XPS) results certify that the the valence state of Ni 3+ is partly reduced to Ni 2+ and residual lithium acts as stable LiBr instead of unstable Li 2 CO 3 at the surface of Br ‒ modified NCA cathode materials. From the electrochemical tests, 0.2 mol% Br − modified NCA with reduced potential polarization, decreasing value of R sf + R ct and increasing Li + diffusion coefficient , exhibits excellent cycling performance, even at elevated temperature. These results clearly indicate that Br − modification contributes to the remarkable enhancement of structure stability and cycling performance of NCA.
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