98-89-5Relevant articles and documents
Stahl,Balaceanu
, p. 684 (1958)
Ring hydrogenation of aromatic compounds in aqueous suspensions of an Rh-loaded TiO2 photocatalyst without use of H2 gas
Nakanishi, Kousuke,Yagi, Ryosuke,Imamura, Kazuya,Tanaka, Atsuhiro,Hashimoto, Keiji,Kominami, Hiroshi
, p. 139 - 146 (2018)
There are various possibilities of co-catalyst-assisted photocatalytic reduction (CPR) over a titanium(iv) oxide (TiO2) photocatalyst, especially H2-free and chemoselective CPR. We examined the photoinduced ring hydrogenation of aromatics having a carboxyl group over metal-loaded TiO2 under H2-free conditions and found that the aromatics were almost quantitatively hydrogenated to the corresponding cyclohexanes having a carboxyl group when rhodium, water and oxalic acid were used as a metal co-catalyst, solvent and hole scavenger, respectively. The effects of different metal co-catalysts, solvents and hole scavengers on the ring hydrogenation were also examined. Based on the results obtained under various conditions, the light dependency and adsorption behavior of the aromatics and hole scavengers, the functions of TiO2 and the co-catalyst, and the reaction process are discussed.
Boosting Catalysis of Pd Nanoparticles in MOFs by Pore Wall Engineering: The Roles of Electron Transfer and Adsorption Energy
Chen, Dongxiao,Yang, Weijie,Jiao, Long,Li, Luyan,Yu, Shu-Hong,Jiang, Hai-Long
, (2020)
The chemical environment of metal nanoparticles (NPs) possesses significant influence on their catalytic performance yet is far from being well understood. Herein, tiny Pd NPs are encapsulated into the pore space of metal–organic frameworks (MOFs), UiO-66-X (X = H, OMe, NH2, 2OH, 2OH(Hf)), affording Pd@UiO-66-X composites. The surface microenvironment of the Pd NPs is readily modulated by pore wall engineering, via the functional group and metal substitution in the MOFs. Consequently, the catalytic activity of Pd@UiO-66-X follows the order of Pd@UiO-66-OH > Pd@UiO-66-2OH(Hf) > Pd@UiO-66-NH2 > Pd@UiO-66-OMe > Pd@UiO-66-H toward the hydrogenation of benzoic acid. It is found that the activity difference is not only ascribed to the distinct charge transfer between Pd and the MOF, but is also explained by the discriminated substrate adsorption energy of Pd@UiO-66-X (–OH 2 –OMe –H), based on CO-diffuse reflectance infrared Fourier transform spectra and density-functional theory (DFT) calculations. The Pd@UiO-66-OH, featuring a high Pd electronic state and moderate adsorption energy, displays the highest activity. This work highlights the influence of the surface microenvironment of guest metal NPs, the catalytic activity of which is dominated by electron transfer and the adsorption energy, via the systematic substitution of metal and functional groups in host MOFs.
Highly effective Ir-based catalysts for benzoic acid hydrogenation: Experiment- and theory-guided catalyst rational design
Tang, Minghui,Mao, Shanjun,Li, Xuefeng,Chen, Chunhong,Li, Mingming,Wang, Yong
, p. 1766 - 1774 (2017)
On the way to exploring superior hydrogenation catalysts, Ir-based catalysts with a record catalytic activity (up to 40 h-1) for the hydrogenation of benzoic acid to cyclohexanecarboxylic acid under mild reaction conditions (85 °C, 0.1 MPa H2, in water) have been successfully developed. By excluding various factors, the experimental results showed that the main factor governing the activity discrepancy between the Ir-based catalysts is actually the dispersion stability of the supports (such as N-doped carbon, active carbon, SBA-15 and various metal oxides) in the reaction solution, rather than the interaction between the Ir active component and the supports. Combined with theoretical investigation from first principles, an activity volcano curve considering the competing adsorption between the reactants (H2) and solvent (H2O) for aqueous aromatic ring hydrogenation was presented for the first time. The high activity of Ir can be deduced by the proper discrepancy of dissociation energies or adsorption energies between H2 and H2O on the catalysts. This activity volcano curve provides guidance for further rational design of promising catalysts for benzoic acid or even aromatic ring hydrogenation under true reaction conditions for practical applications.
A highly dispersed and stable Ni/mSiO2-AE nanocatalyst for benzoic acid hydrogenation
Zhang, Huiling,Gao, Xuejia,Ma, Yuanyuan,Han, Xue,Niu, Libo,Bai, Guoyi
, p. 5993 - 5999 (2017)
A Ni/mSiO2-AE nanocatalyst was successfully prepared via loading the active nickel species on mSiO2 by an ammonia evaporation (AE) method. It exhibited excellent catalytic performance in the selective hydrogenation of benzoic acid with the conversion of benzoic acid and selectivity to cyclohexane carboxylic acid being 98.9% and 99.1%, respectively. Furthermore, the catalyst can be recycled four times without appreciable loss of its initial activity. As demonstrated by TEM, the active nickel species was highly dispersed with an average particle size of 3.2 nm in this nanocatalyst, which is much smaller than that of Ni/mSiO2-IMP (～18 nm), prepared by a conventional impregnation method. TPR and XPS results revealed the existence of a stronger interaction between the active nickel species and the mSiO2 support in Ni/mSiO2-AE, compared to Ni/mSiO2-IMP. This strong metal-support interaction in Ni/mSiO2-AE can effectively suppress the loss of the active nickel species during the reaction, resulting in its good stability under relatively harsh reaction conditions.
Gram-scale synthesis of carboxylic acids via catalytic acceptorless dehydrogenative coupling of alcohols and hydroxides at an ultralow Ru loading
Chen, Cheng,Cheng, Hua,Verpoort, Francis,Wang, Zhi-Qin,Wu, Zhe,Yuan, Ye,Zheng, Zhong-Hui
, (2021/12/13)
Acceptorless dehydrogenative coupling (ADC) of alcohols and water/hydroxides is an emergent and graceful approach to produce carboxylic acids. Therefore, it is of high demand to develop active and practical catalysts/catalytic systems for this attractive transformation. Herein, we designed and fabricated a series of cyclometallated N-heterocyclic carbene-Ru (NHC-Ru) complexes via ligand tuning of [Ru-1], the superior complex in our previous work. Gratifyingly, gram-scale synthesis of carboxylic acids was efficiently enabled at an ultralow Ru loading (62.5 ppm) in open air. Moreover, effects of distinct ancillary NHC ligands and other parameters on this catalytic process were thoroughly studied, while further systematic studies were carried out to provide rationales for the activity trend of [Ru-1]-[Ru-7]. Finally, determination of quantitative green metrics illustrated that the present work exhibited superiority over representative literature reports. Hopefully, this study could provide valuable input for researchers who are engaging in metal-catalyzed ADC reactions.
Synthesis of β-nitro ketones from geminal bromonitroalkanes and silyl enol ethers by visible light photoredox catalysis
Cao, Haoying,Ma, Shanshan,Feng, Yanhong,Guo, Yawen,Jiao, Peng
supporting information, p. 1780 - 1783 (2022/02/17)
Various β-nitro ketones, including those bearing a β-tertiary carbon, were prepared from geminal bromonitroalkanes and trimethylsilyl enol ethers of a broad range of ketones by visible light photoredox catalysis, which were then easily converted into β-amino ketones, 1,3-amino alcohols, α,β-unsaturated ketones, β-cyano ketones and γ-nitro ketones.
Cobalt-Catalyzed Deprotection of Allyl Carboxylic Esters Induced by Hydrogen Atom Transfer
Li, Nan,Gui, Yizhen,Chu, Mengqi,You, Mengdi,Qiu, Xiaohan,Liu, Hejia,Wang, Shiang,Deng, Meng,Ji, Baoming
supporting information, p. 8460 - 8464 (2021/11/13)
A brief, efficient method has been developed for the removal of the allyl protecting group from allyl carboxylic esters using a Co(II)/TBHP/(Me2SiH)2O catalytic system. This facile strategy displays excellent chemoselectivity, functional group tolerance, and high yields. This transformation probably occurs through the hydrogen atom transfer process, and a Co(III)-six-membered cyclic intermediate is recommended.
