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Covalent organic framework as an efficient, metal-free, heterogeneous photocatalyst for organic transformations under visible light
摘要： Visible-light active, heterogeneous, and organic photocatalysts exhibit a more sustainable and environmentally friendly alternative to classical metal-based catalysts. Two-dimensional covalent organic frameworks (2D-COFs) with permanent porosity, columnar π-arrays and excellent stability, that can become an excellent platform for heterogeneous photocatalysis of organic transformations. Here we report a predesigned imine-based COF with electron donor and acceptor structure. And new framework possesses large surface area, high crystallinity, outstanding stability and broad absorption range in the visible-light region as well as good photoelectric response characteristics. Importantly, it was found to be a highly effective heterogeneous photocatalyst for reductive dehalogenation of phenacyl bromide derivatives and α-alkylation of aldehydes under irradiation of visible-light. In addition, the COF gave good recyclability and could be reused after a simple separation manipulation. The current present still reveals a great prospect for 2D-COFs as metal-free, heterogeneous photocatalysts for organic transformations.
关键词： visible light,photocatalysis,heterogeneous catalysis,metal-free,covalent organic frameworks
更新于2025-09-23 15:23:52
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Superior photocatalytic activity of tungsten disulfide nanostructures: role of morphology and defects
摘要： Tungsten disulphide (WS2) nanostructures, WS2 nanosheets (WNS) and WS2 nanorods (WNR), were synthesized by varying the surfactant, N-cetyl-N,N,N-trimethyl ammonium bromide (CTAB), concentration using facile hydrothermal technique. Samples were characterized by high-resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM) for morphology, X-ray diffraction (XRD) to confirm their phase and crystal structure, photoluminescence (PL) and Raman studies for the determination of defect density, Tauc plot for the determination of band gap, Fourier transform infra red (FTIR) spectroscopy for functional groups and bonds, and Brunauer–Emmett–Teller (BET) isotherms for the determination of pore size and surface area. A comparative study using WS2 nanostructures (WNS and WNR) was conducted to observe the photocatalytic degradation efficiency (?) and degradation kinetics on methylene blue (MB) and 4-chlorophenol (4-CP). The superior photocatalytic performance of WNS over WNR is attributed to enhanced pore size and reduced defect density. High-performance liquid chromatography was carried out for the determination of intermediate products during photocatalytic degradation.
关键词： Raman,High-performance liquid chromatography,WS2 nanostructures,Photoluminescence,Photocatalysis
更新于2025-09-23 15:23:52
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Photocatalytic oxidation of gaseous benzene, toluene and xylene under UV and visible irradiation over Mn-doped TiO2 nanoparticles
摘要： The photocatalytic oxidation of gaseous benzene, toluene and xylene (BTX) over un-doped, 0.1 and 1 wt% Mn-TiO2 nanoparticles under ultraviolet and visible irradiation was studied in atmosphere of synthetic air or inert gas. The photocatalytic decomposition efficiency and the oxidation products were determined using a Static Photochemical Reactor coupled with FTIR spectroscopy. BTX underwent efficient decomposition over Mn-TiO2 photocatalysts under UV irradiation, more with oxygen presence and less without oxygen. More important toluene and xylene went substantial decomposition over 0.1 mol% Mn-TiO2 under visible irradiation with oxygen presence. The main final oxidation products in the UV photocatalysis of BTX were CO2, CO and H2O, with CO2 and CO yields 4 and 2 respectively. The conversion percentage of benzene, toluene, and xylene to CO2 were 63.6%, 56.4%, 51.8%, and to CO 29%, 26.5%, 23.2%, respectively. In the visible photocatalysis of toluene and xylene the yields of CO were insignificant. Formation of carbon containing deposits on TiO2 surfaces was observed after extensive UV photocatalysis of toluene and xylene, and such by-products surface coverage may reduce the photocatalytic activity of TiO2 samples. Some aspects of the photocatalytic mechanism were examined.
关键词： Mn-doped TiO2,Visible - light photocatalysis,Photodegradation of Benzene,Indoors air pollution,Xylene,Toluene
更新于2025-09-23 15:23:52
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A sustainable solution for removal of glutaraldehyde in saline water with visible light photocatalysis
摘要： Glutaraldehyde (GA) is the most common biocide used in unconventional oil and gas production. Photocatalytic degradation of GA in brine simulating oil and gas produced water using Ag/AgCl/BiOCl composite as a photocatalyst with visible light was investigated. Removal of GA at 0.1 mM in 200 g/L NaCl solution at pH 7 was 90% after 75 min irradiation using 5 g/L of the photocatalyst. The GA removal followed pseudo-first order reaction with a rate constant of 0.0303 min?1. At pH 5 or at 300 g/L NaCl, the photocatalytic removal of GA was almost completely inhibited. Similar inhibitions were observed when adding dissolved organic carbon (from humic acid) at 10 and 200 mg/L, or Br? at 120 mg/L to the system. The removal rate of GA markedly increased with increasing pH (5-9), photocatalyst loading (2-8 g/L) and under 350 nm UV (compared to visible light). On the contrary, the removal rate of GA markedly decreased with increasing NaCl and initial GA concentrations (0-300 g/L for NaCl and 0.1-0.4 mM for GA). A quenching experiment was also conducted; electron holes (h+) and superoxide (O2?-) were found as the main reactive species responsible for the removal of GA while ?OH had a very limited effect.
关键词： saline,Glutaraldehyde,produced water,hydraulic fracturing fluid,visible light photocatalysis
更新于2025-09-23 15:23:52
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Surface-Immobilized Conjugated Polymers Incorporating Rhenium Bipyridine Motifs for Electrocatalytic and Photocatalytic CO <sub/>2</sub> Reduction
摘要： The solar-driven conversion of CO2 to value-added products provides a promising route for solar energy storage and atmospheric CO2 remediation. In this report, a variety of supporting electrode materials were successfully modified with a [2,2′-bipyridine]-5,5′-bis(diazonium) rhenium complex through a surface-localized electropolymerization method. Physical characterization of the resulting multilayer films confirms that the coordination environments of the rhenium bipyridine tricarbonyl sites are preserved upon immobilization and that the polymerized catalyst moieties exhibit long-range structural order with uniform film growth. UV?vis studies reveal additional absorption bands in the visible region for the polymeric films that are not present in the analogous rhenium bipyridine complexes. Electrochemical studies with modified graphite rod electrodes show that the electrocatalytic activity of these films increases with catalyst loading up to an optimal value, beyond which electron and mass transport through the material become rate-limiting. Electrocatalytic studies performed at ?2.25 V vs Fc/Fc+ for 2 h reveal CO production with faradaic efficiencies and turnover numbers up to 99% and 3606, respectively. Photocatalytic studies of the modified TiO2 devices demonstrate enhanced activity at low catalyst loadings, with turnover numbers up to 70 during 5 h of irradiation.
关键词： metallopolymers,surface modification,photocatalysis,rhenium bipyridine,solar energy conversion,electrocatalysis
更新于2025-09-23 15:23:52
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Comparing the Efficiency of N-Doped TiO2 and N-Doped Bi2MoO6 Photo Catalysts for MB and Lignin Photodegradation
摘要： In this study, we tested the efficiency of nitrogen-doped titanium dioxide (N-TiO2) and nitrogen-doped bismuth molybdate (N-Bi2MoO6) compounds as photocatalysts capable of degrading methylene blue and lignin molecules under irradiation with ultraviolet (UV) and visible light (VIS). Moreover, we compared TiO2 and Bi2MoO6 catalysts with N-TiO2 and N-Bi2MoO6 compounds using chemical coprecipitation. The catalysts were prepared starting from Ti(OCH2CH2CH3)4, Bi(NO3)3·5H2O, and (NH4)6Mo7O24 reagents. N-doping was achieved in a continuous reflux system, using ethylene diamine as a nitrogen source. The resulting materials were characterized using Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Additionally, we observed the decrease in particle size after processing the compounds in the reflux system. The results regarding photocatalytic degradation tests show a remarkable effect for nitrogen doped samples, achieving 90% of lignin degradation.
关键词： photocatalysis,lignin,visible light,UV light,bismuth molybdate,Titanium dioxide
更新于2025-09-23 15:23:52
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A 3D metal-organic framework with isophthalic acid linker for photocatalytic properties
摘要： The efficient removal of organic pollutants from wastewater is a hot research topic due to its ecological and environmental importance. Herein, by using the ligand-truncation and functionalization strategy, a Cu(II)-based 3D metal-organic framework [Cu2(L1)?5DMF]n (1) (H4L1 =3,5-di(3,5-dicarboxyphenyl)nitrobenzene), has been designed, prepared and characterized. The single crystal X-ray diffraction results indicates that MOF 1 possess a 3D framework with 1D hexangular channels. The MOF 1 has been used as photocatalyst for the photodegradation of organic dyes viz. methyl violet (MV) and Rhodamine B (Rh B). The photocatalytic results indicated that 1 offered better photocatalysis towards the photodegradation of MV in comparison to Rh B. The probable mechanism for the photocatalytic activity of 1 has been addressed using density of states (DOS) and partial DOS calculations.
关键词： density of states,photocatalysis,Dye,MOF
更新于2025-09-23 15:23:52
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Hydrophobic Metal Halide Perovskites for Visible-Light Photoredox C-C Bond Cleavage and Dehydrogenation Catalysis
摘要： Two-dimensional lead and tin halide perovskites were prepared by intercalating the long alkyl group 1-hexadecylammonium (HDA) between the inorganic layers. We observed visible-light absorption, narrow-band photoluminescence, and nanosecond photoexcited lifetimes in these perovskites. Due to their hydrophobicity and stability even in humid air, we applied these perovskites in the decarboxylation and dehydrogenation of indoline acids using (HDA)2PbI4 or (HDA)2SnI4 as photoredox catalysts, with quantitative conversions and high yields for the former. We highlight another original application of the metal halide perovskites.
关键词： photocatalysis,2D metal halide perovskites,decarboxylation,photooxidation,hydrophobic perovskite
更新于2025-09-23 15:23:52
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Regulating Charge-Transfer in Conjugated Microporous Polymer for Photocatalytic Hydrogen Evolution
摘要： Band gap engineering in donor-acceptor conjugated microporous polymers is a potential way to increase the solar energy harvesting towards photochemical water splitting. Herein, we report design and synthesis of a series of donor-acceptor CMPs [tetraphenylethylene (TPE) = donor and 9-fluorenone (F) = acceptor], F0.1CMP, F0.5CMP and F2.0CMP which exhibit tunable band gaps and photocatalytic hydrogen evolution from water. The donor-acceptor CMPs exhibit intramolecular charge transfer (ICT) absorption in the visible region (λmax=480 nm) and their band gap is finely tuned from 2.8 eV to 2.1 eV by increasing the 9-fluorenone content. Interestingly, they also show charge transfer emissions (in 540 -580 nm range), assisted by the energy transfer from the other TPE segments (not involved in CT interaction) as evidenced from fluorescence lifetime decay analysis. By increasing the 9-fluorenone content the emission color of the polymer is also tuned from green to red. Photocatalytic activities of the donor-acceptor CMPs (F0.1CMP, F0.5CMP and F2.0CMP) are greatly enhanced compared to the 9-fluorenone free polymer (F0.0CMP) which is essentially due to improved visible light absorption and low band gap of donor-acceptor CMPs. Among all the polymers F0.5CMP with an optimum band gap (2.3 eV) shows highest H2 evolution under visible light irradiation. Moreover, all the polymers show excellent dispersibility in organic solvents and also they are easily processed onto solid substrates.
关键词： Visible-light absorption,Conjugated polymers,Photocatalysis,Charge transfer,Energy transfer
更新于2025-09-23 15:23:52
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Wide Spectrum Photocatalytic Activity in Lanthanide-doped Upconversion Nanophosphors Coated with Porous TiO2 and Ag-Cu Bimetallic Nanoparticles
摘要： Approaches towards maximum utilization of solar light spectrum for photocatalysis have currently attracted great interest. The combination of profoundly different properties, such as, upconversion, semiconducting and plasmonic properties can produce a favorable path in efficient utilization of the different regions of solar light reaching to earth. In this regard, design and fabrication of microstructures consisting of upconverting lanthanide doped nanophosphors coated with porous semiconducting material, TiO2 and decorated with plasmonic Ag-Cu bimetallic nanoparticles is presented in this work. These microstructures display great stability and exceptional photocatalytic activity by absorbing wide spectrum from ultraviolet to near infrared. The photocatalytic activity could be attributed to the synergistic effects between the different components and the efficient energy transfer between them. The development of such sort of hybrid microstructures could pave way for the development of new materials for the efficient utilization of the wide spectrum of sunlight.
关键词： bimetallic plasmonic nanoparticles,titania,wide spectrum utilization,photocatalysis,Upconversion nanophosphors
更新于2025-09-23 15:23:52