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1.
Rosalina Lara-Rico Elia M. Múzquiz-Ramos Claudia M. Lpez-Badillo Ulises M. García-Prez Brenda R. Cruz-Ortiz 《RSC advances》2019,9(5):2792
Goethite–titania (α-FeOOH–TiO2) composites were prepared by co-precipitation and mechanical milling. The structural, morphological and optical properties of as-synthesized composites were characterized by X-ray powder diffraction, scanning electron microscopy and UV-Vis diffuse reflectance spectroscopy, respectively. α-FeOOH–TiO2 composites and TiO2-P25, as reference, were evaluated as photocatalysts for the disinfection of Escherichia coli under UV or visible light in a stirred tank reactor. α-FeOOH–TiO2 exhibited better photocatalytic activity in the visible region than TiO2-P25. The mechanical activation increased the absorption in the visible range of TiO2-P25 and the photocatalytic activity of α-FeOOH–TiO2. In the experiments with UV light and α-FeOOH–TiO2, mechanically activated, a 5.4 log-reduction of bacteria was achieved after 240 min of treatment. Using visible light the α-FeOOH–TiO2 and the TiO2-P25 showed a 3.1 and a 0.7 log-reductions at 240 min, respectively. The disinfection mechanism was studied by ROS detection and scavenger experiments, demonstrating that the main ROS produced in the disinfection process were superoxide radical anion, singlet oxygen and hydroxyl radical.A photocatalytic mechanism for FeOOH–TiO2 composite is proposed under UV-Vis light, the FeOOH–TiO2 composite showed higher photocatalytic activity than TiO2-P25. 相似文献
2.
Marisa Rico-Santacruz Patricia García-Muoz Clment Marchal Nelly Batail Charlotte Pham Didier Robert Nicolas Keller 《RSC advances》2020,10(7):3817
Coating-free TiO2@β-SiC photocatalytic composite foams gathered within a ready-to-use shell/core alveolar medium the photocatalytically active TiO2 phase and the β-SiC foam structure were prepared via a multi-step shape memory synthesis (SMS) replica method. They were fabricated following a sequential two-step carburization approach, in which an external TiC skin was synthesized at the surface of a β-SiC skeleton foam obtained from a pre-shaped polyurethane foam during a first carburization step. The adsorption behaviour of the shell/core TiO2@β-SiC composite foams towards the Diuron pollutant in water was tuned by submitting the carbide foams to a final calcination treatment within the 550–700 °C temperature range. The controlled calcination step allowed (i) the selective oxidation of the TiC shell into a TiO2 crystallite shell owing to the β-SiC resistance to oxidation and (ii) the amount of residual unreacted carbon in the foams to be tuned. The lower the calcination temperature, the more pronounced the adsorption profiles of the composites and the higher the Diuron amount removed by adsorption on the residual unreacted carbon. The ready-to-use TiO2@β-SiC composite foams were active in the degradation of the Diuron pesticide, without any further post-synthesis immobilization or synthesis process at the foam surface. They displayed good reusability with test cycles and benefitted from an enhanced stability in terms of the titania release to water.Coating-free TiO2@β-SiC photocatalytic composite foams gathering within a ready-to-use shell/core alveolar medium the TiO2 photocatalyst and the β-SiC foam structure were prepared via a multi-step shape memory synthesis (SMS) replica method. 相似文献
3.
Digambar B. Bankar Ranjit R. Hawaldar Sudhir S. Arbuj Mansur H. Moulavi Santosh T. Shinde Shrikant P. Takle Manish D. Shinde Dinesh P. Amalnerkar Kaluram G. Kanade 《RSC advances》2019,9(56):32735
One-pot green synthesis of propargylamines using ZnCl2 loaded TiO2 nanomaterial under solvent-free conditions has been effectively accomplished. The aromatic aldehydes, amines, and phenylacetylene were reacted at 100 °C in the presence of the resultant catalyst to form propargylamines. The nanocrystalline TiO2 was initially synthesized by a sol–gel method from titanium(iv) isopropoxide (TTIP) and further subjected to ZnCl2 loading by a wet impregnation method. X-ray diffraction (XRD) patterns revealed the formation of crystalline anatase phase TiO2. Field emission scanning electron microscopy (FESEM) showed the formation of agglomerated spheroid shaped particles having a size in the range of 25–45 nm. Transmission electron microscopy (TEM) validates cubical faceted and nanospheroid-like morphological features with clear faceted edges for the pure TiO2 sample. Surface loading of ZnCl2 on spheroid TiO2 nanoparticles is evident in the case of the ZnCl2 loaded TiO2 sample. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Ti4+ and Zn2+ species in the ZnCl2 loaded TiO2 catalyst. Energy-dispersive X-ray (EDS) spectroscopy also confirmed the existence of Ti, O, Zn and Cl elements in the nanostructured catalyst. 15% ZnCl2 loaded TiO2 afforded the highest 97% yield for 3-(1-morpholino-3-phenylprop-2-ynyl)phenol, 2-(1-morpholino-3-phenylprop-2-ynyl)phenol and 4-(1,3-diphenylprop-2-ynyl)morpholine under solvent-free and aerobic conditions. The proposed nanostructure-based heterogeneous catalytic reaction protocol is sustainable, environment-friendly and offers economic viability in terms of recyclability of the catalyst.A one-pot green synthesis of propargylamines using nanostructured ZnCl2–TiO2 under solvent-free conditions has been effectively accomplished. The proposed reaction protocol is sustainable, environment-friendly and offers economic viability. 相似文献
4.
The first use of biomass-derived HMF in the one-pot Kabachnik–Fields reaction is reported here. A wide range of furan-based α-amino phosphonates were prepared in moderate to excellent yields under mild, effective and environmentally-benign conditions: iodine as a non-metal catalyst, biobased 2-MeTHF as the solvent and room or moderate temperature. The hydroxymethyl group of HMF persists in the Kabachnik–Fields products, widening the scope of further modification and derivatization compared to those arising from furfural. Issues involving the diastereoselectivity and double Kabachnik–Fields condensation were also faced.A mild and efficient one-pot protocol for the synthesis of α-amino phosphonates directly from 5-HMF was described.Recently, the production of chemicals from renewable biomass has attracted growing interests due to the dwindling reserves of fossil resources and the increasing awareness of environmental concerns.1 5-Hydroxymethylfurfural (HMF), a promising primary biomass-derived platform chemical readily obtained from acid-catalyzed dehydration of six-carbon carbohydrates, displays a strong potential in organic synthesis.2 Besides the well-developed conversions of HMF towards monomers and biofuels via oxidation or reduction reactions,3 some remarkable strategies converting HMF to high value-added fine chemicals have been disclosed.4 Nevertheless, the specific reactivity and reduced stability of HMF, in comparison with the pentose-derived furfural homolog, have limited its use in synthetic applications.5 Furthermore, its commercial availability, though not anymore a barrier nowadays, has limited the number of investigations in the past. In this regard, developing efficient and economic routes to existing or novel fine chemicals from HMF, with its different reactivity compared to simpler aldehydes, is still a challenge.Multi-component reactions (MCRs) are extremely convenient and efficient strategies to prepare highly functionalized compounds from simple starting materials by one-pot procedures. Since they have many advantages, such as high atom economy, high convergence, time and energy saving, MCRs have gained much attention in modern synthetic organic chemistry.6 Nevertheless, to our knowledge, the direct utilization of HMF in MCR processes has been only rarely explored.α-Amino phosphonates, due to the structural analogy to natural α-amino acids and their significant biological activities, such as antitumor, antitubercular, cytotoxic activities, and so on,7 have been the subject of considerable interest in the past decades both in synthetic organic and medicinal chemistry.8 Among several methods for preparing α-amino phosphonates, the Kabachnik–Fields reaction, a one-pot condensation of an aldehyde, an amine and a dialkyl phosphite is the most effective and convenient strategy.9 A large number of conditions have been reported for the acid-catalyzed (Lewis/Brønsted)10 and catalyst-free11 Kabachnik–Fields reaction, affording the α-amino phosphonates from various aldehydes. However, none of studies have included HMF as a substrate in their scope although the products from HMF can offer more possibilities for further functionalization, thanks to its CH2OH appendage. The sole synthesis of α-amino phosphonates from HMF was reported by Cottier and Skowroński in a two-step reaction strategy, consisting in pre-formation of the imine which upon isolation reacted with dialkyl phosphites as nucleophilic species at high temperature using trifluoroacetic acid as catalyst.12 Thus, a milder and more direct procedure for the synthesis of α-amino phosphonates from HMF is still to be developed.As part of our on-going interest on the application of HMF towards fine chemicals and on green and sustainable chemistry,13 we explored the possibility to synthesize furan-based α-amino phosphonates via the one-pot Kabachnik–Fields condensation, directly from HMF.For this study, we selected molecular iodine as a mild and effective Lewis acid catalyst, as often used in multicomponent synthesis because of its operational simplicity, low cost and toxicity and likely to be compatible with HMF sensitivity to acidic conditions.14 Wu and co-workers have confirmed its efficiency in Kabachnik–Fields reactions of simple aldehydes such as benzaldehyde and furfural.15 The primary set of experimental conditions has been fixed as 5 mol% iodine in ethanol [0.5 M] with equimolar stoichiometric ratio of all partners (HMF, aniline, diethyl phosphite). The corresponding Kabachnik–Fields product 4a was obtained in 71% isolated yield after 24 h, together with around 11% of unreacted HMF and 6% of the intermediate imine ( Entry Cat. loading Solvent [0.5 M] Temp. Ratio 1a/2a/3a Time Isolated yield 1 5 mol% EtOH 25 °C 1 : 1 : 1 24 h 71% 2 5 mol% MeCN 25 °C 1 : 1 : 1 24 h 60% 3 5 mol% DCM 25 °C 1 : 1 : 1 24 h 31% 4 5 mol% THF 25 °C 1 : 1 : 1 24 h 84% 5 5 mol% 2-MeTHF 25 °C 1 : 1 : 1 24 h 74% 6 5 mol% THF 25 °C 1 : 1 : 1.5 24 h 90% 7 5 mol% 2-MeTHF 25 °C 1 : 1 : 1.5 8 h 91% 8 2.5 mol% 2-MeTHF 25 °C 1 : 1 : 1.5 8 h 77% 9 1 mol% 2-MeTHF 25 °C 1 : 1 : 1.5 8 h 61% 10 — 2-MeTHF 25 °C 1 : 1 : 1.5 8 h 54% (80%)b 11 5 mol% 2-MeTHF 50 °C 1 : 1 : 1.5 4 h 83% 12 5 mol% 2-MeTHF 78 °C 1 : 1 : 1 3 h 71%