Covalent organic frameworks(COFs)are nanoporous crystalline polymers with densely conjugated structures.This work discovers that imine-linked COFs exhibit remarkable photodegradation efficiency to azo dyes dissolved i...Covalent organic frameworks(COFs)are nanoporous crystalline polymers with densely conjugated structures.This work discovers that imine-linked COFs exhibit remarkable photodegradation efficiency to azo dyes dissolved in water.Visible light generates different types of radicals from COFs,and superoxide radicals break N=N bonds in dye molecules,resulting in 100%degradation of azo dyes within 1 h.In contrast,these dyes cannot be degraded by conventionally used photocatalysts,for example,TiO2.Importantly,the COF photocatalysts can be recovered from the dye solutions and re-used to degrade azo dyes for multiple times without loss of degradation efficiency.This work provides an efficient strategy to degrade synthetic dyes,and we expect that COFs with designable structures may use as new photocatalysts for other important applications.展开更多
The dye-sensitized TiO2 method is one of the most promising methods for the visible-light-induced detoxification of pollutants. The reaction mechanism for photocatalytic degradation of orange II (OII) and rhodamine B ...The dye-sensitized TiO2 method is one of the most promising methods for the visible-light-induced detoxification of pollutants. The reaction mechanism for photocatalytic degradation of orange II (OII) and rhodamine B (RhB) with self-sensitized TiO2 under visible light irradiation (λ > 400 nm) has been evaluated. Radical scavenger studies were carried out to investigate the active species involved in the photodegradation of 5 mg/L of initial concentration of OII and RhB at room temperature. The trapping effects of different scavengers results proved that the oxidation of OII and RhB mainly occurred by the direct oxidization of h+ and ·O2- radicals, while the ·OH radicals played only a relatively minor role in the direct oxidization process.展开更多
Photocatalytic oxidation(PCO) process is an effective way to deal with organic pollutants in wastewater which could be difficult to be degraded by conventional biological treatment methods. Normally the TiO 2 powder ...Photocatalytic oxidation(PCO) process is an effective way to deal with organic pollutants in wastewater which could be difficult to be degraded by conventional biological treatment methods. Normally the TiO 2 powder in nanometre size range was directly used as photocatalyst for dye degradation in wastewater. However the titanium dioxide powder was arduous to be recovered from the solution after treatment. In this application, a new form of TiO 2(i. e. pillar pellets ranging from 2 5 to 5 3 mm long and with a diameter of 3 7 mm) was used and investigated for photocatalytic degradation of textile dye effluent. A test system was built with a flat plate reactor(FPR) and UV light source(blacklight and solar simulator as light source respectively) for investigating the effectiveness of the new form of TiO 2. It was found that the photocatalytic process under this configuration could efficiently remove colours from textile dyeing effluent. Comparing with the TiO 2 powder, the pellet was very easy to recovered from the treated solution and can be reused in multiple times without the significant change on the photocatalytic property. The results also showed that to achieve the same photocatalytic performance, the FPR area by pellets was about 91% smaller than required by TiO 2 powder. At least TiO 2 pellet could be used as an alternative form of photocatalyst in applications for textile effluent treatment process, also other wastewater treatment processes.展开更多
H3PW12O40/TiO2-SiO2 was synthesized by impregnation method which significantly improved the catalytic activity under simulated natural light. The prop- erties of the samples were characterized by Fourier trans- form i...H3PW12O40/TiO2-SiO2 was synthesized by impregnation method which significantly improved the catalytic activity under simulated natural light. The prop- erties of the samples were characterized by Fourier trans- form infrared spectra （FTIR）, X-ray powder diffraction pattern （XRD）, Scanning electron micrographs （SEM）, and Zeta potential. Degradation of methyl violet was used as a probe reaction to explore the influencing factors on the photodegradation reaction. The results show that the opti- mal conditions are as follows： initial concentration of methyl violet of 10 mg·L^-1, pH of 3.0, catalyst dosage of 2.9 g·L^-1, and light irradiation time of 2.5 h. Under these conditions, the degradation rate of methyl violet is 95.4 %. The reaction on photodegradation for methyl violet can be expressed as the first-order kinetic model, and the possible mechanism for the photocatalysis under simulated natural light is suggested. After used continuously for five times, the catalyst keeps the inherent photocatalytic activity for degradation of dyes. The photodegradation of methyl orange, methyl red, naphthol green B, and methylene blue was also tested, and the degradation rate of dyes can reach 81%-100%.展开更多
Topochemical polymerization of molecular crystals into porous materials is of significance due to their promising applications in the field of adsorption and catalysis,yet rarely reported due to the synthesis difficul...Topochemical polymerization of molecular crystals into porous materials is of significance due to their promising applications in the field of adsorption and catalysis,yet rarely reported due to the synthesis difficulty.Herein,a hydrogen-bonded organic framework(HOF-45)has been fabricated by the crystallization of a cage-like building block containing three alkynyl groups.It exhibits almost mesoporous structure demonstrated by single crystal X-ray diffraction study.Light-driven topochemical polymerization of HOF-45 with ethanedithiol covalently links alkynyl groups in HOF-45,generating a hydrogen-bond and covalentbond cross-linked material(HOF-45C).In contrast to HOF-45,cross-linked HOF-45C retains the crystalline nature and displays improved solution resistence according to the powder X-ray diffraction data.In particular,HOF-45C is able to support the growth of ultrafine palladium nanoparticles with the average size of ca.1.9 nm for rapidly promoting the degradation of nitrophenol,methyl orange,and congo red with the help of NaBH_(4)as well as Suzuki-Miyaura coupling reaction.This work inputs a new idea on the HOFs application in preparing covalent-linked porous organic materials.展开更多
Highly active mesoporous TiO_2 of about 6 nm crystal size and 280.7 m^2/g specific surface areas has been successfully synthesized via controlled hydrolysis of titanium butoxide at acidic medium. It was characterized ...Highly active mesoporous TiO_2 of about 6 nm crystal size and 280.7 m^2/g specific surface areas has been successfully synthesized via controlled hydrolysis of titanium butoxide at acidic medium. It was characterized by means of XRD（X-ray diffraction）, SEM（scanning electron microscopy）, TEM（transmission electron microscopy）, FT-IR（Fourier transform infrared spectroscopy）, TGA（thermogravimetric analysis）, DSC（differential scanning calorimetry） and BET（Brunauer–Emmett–Teller） surface area. The degradation of dichlorophenol-indophenol（DCPIP） under ultraviolet（UV） light was studied to evaluate the photocatalytic activity of samples. The effects of different parameters and kinetics were investigated. Accordingly, a complete degradation of DCPIP dye was achieved by applying the optimal operational conditions of 1 g/L of catalyst, 10 mg/L of DCPIP, pH of 3 and the temperature at 25 ± 3°C after 3 min under UV irradiation. Meanwhile, the Langmuir–Hinshelwood kinetic model described the variations in pure photocatalytic branch in consistent with a first order power law model.The results proved that the prepared TiO_2 nanoparticle has a photocatalytic activity significantly better than Degussa P-25.展开更多
Understanding the degradation behavior of azo dyes in photocatalytic wastewater treatment is of fundamental and practical importance for their application in textile-processing and other coloration industries. In this...Understanding the degradation behavior of azo dyes in photocatalytic wastewater treatment is of fundamental and practical importance for their application in textile-processing and other coloration industries. In this study, quantum chemistry, as density functional theory, was used to elucidate different degradation pathways of azo pyridone dyes in a hydroxyl radical(HO ·)-initiated photocatalytic system. A series of substituted azo pyridone dyes were synthesized by changing the substituent group in the para position of the benzene moiety, ranging from strong electron-donating to strong electron-withdrawing groups. The effect of dye molecular structure on the photocatalytic degradation reaction mechanism was analyzed and quantification of substituent effects on the thermodynamic and kinetics parameters was performed. Potential energy surface analysis revealed the most susceptible reaction site for the HO ·attack. The calculated reaction barriers are found to be strongly affected by the nature of substituent group with a good correlation using Hammett σp constants and experimentally determined reaction rates. The stability of pre-reaction complexes and transition state complexes were analyzed applying the distortion-interaction model. The increased stability of the transition state complexes with the distancing from the substituent group has been established.展开更多
Incautious discharge of organic dyes such as methyl orange(MO)has produced serious pollution to the environment,calling for the efficient techniques to remove them with retaining the green world.The photo-catalytic de...Incautious discharge of organic dyes such as methyl orange(MO)has produced serious pollution to the environment,calling for the efficient techniques to remove them with retaining the green world.The photo-catalytic degradation of organic dyes is promising among the developed techniques.Thus,a strategy based on transpiration-prompted photocatalytic degradation of dye pollutant under sunlight is put forward.Aniline(ANI)is graft-polymerized onto poly(acrylamide-co-N-4-aminophenylacrylamide)(PAAm)cryogel embedded with gold nanoparticles(AuNPs,diameter:4-10 nm).The obtained cryogels integrated with AuNPs and PANI inside PAAm matrix(AuNP@PAAm-g-PANI)have been structurally explored based on the chemical composition and the phase/porous morphology.SEM and TEM observation shows that PANI and AuNPs are uniformly distributed in PAAm matrix.Since the macro-porosity of cryogel,hydrophilicity of PAAm and photo-thermal activity of PANI,PAAm-g-PANI cryogels without AuNPs can have a photo-thermal evaporation rate of water at 1.63 kg·m^(-2)·h^(-1).As a comparison,Au NP@PAAm-g-PANI cryogels with AuNPs exhibit higher one at 2.20 kg·m^(-2)·h^(-1),suggesting the promotion of AuNPs to photo-thermal evaporation.Meanwhile,PANI appreciatively assists AuNPs to display higher catalytic ability for the oxidative degradation of MO.Therefore,the removal of MO from water is obviously prompted by the water transpiration under sunlight with AuNP@PAAm-g-PANI cryogels,whose rate constant can reach to 0.320 h^(-1),being three folds of that for the sole absorption of MO.This transpiration-prompted photocatalytic degradation provides a fascinating route to eliminate organic pollutants and obtain pure water from wastewater simultaneously with sustainable sunlight energy.展开更多
基金financially supported by the National Science Fund for Distinguished Young Scholars (21825803)the Program of Excellent Innovation Teams of Jiangsu Higher Education Institutions and the Project of Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘Covalent organic frameworks(COFs)are nanoporous crystalline polymers with densely conjugated structures.This work discovers that imine-linked COFs exhibit remarkable photodegradation efficiency to azo dyes dissolved in water.Visible light generates different types of radicals from COFs,and superoxide radicals break N=N bonds in dye molecules,resulting in 100%degradation of azo dyes within 1 h.In contrast,these dyes cannot be degraded by conventionally used photocatalysts,for example,TiO2.Importantly,the COF photocatalysts can be recovered from the dye solutions and re-used to degrade azo dyes for multiple times without loss of degradation efficiency.This work provides an efficient strategy to degrade synthetic dyes,and we expect that COFs with designable structures may use as new photocatalysts for other important applications.
文摘The dye-sensitized TiO2 method is one of the most promising methods for the visible-light-induced detoxification of pollutants. The reaction mechanism for photocatalytic degradation of orange II (OII) and rhodamine B (RhB) with self-sensitized TiO2 under visible light irradiation (λ > 400 nm) has been evaluated. Radical scavenger studies were carried out to investigate the active species involved in the photodegradation of 5 mg/L of initial concentration of OII and RhB at room temperature. The trapping effects of different scavengers results proved that the oxidation of OII and RhB mainly occurred by the direct oxidization of h+ and ·O2- radicals, while the ·OH radicals played only a relatively minor role in the direct oxidization process.
文摘Photocatalytic oxidation(PCO) process is an effective way to deal with organic pollutants in wastewater which could be difficult to be degraded by conventional biological treatment methods. Normally the TiO 2 powder in nanometre size range was directly used as photocatalyst for dye degradation in wastewater. However the titanium dioxide powder was arduous to be recovered from the solution after treatment. In this application, a new form of TiO 2(i. e. pillar pellets ranging from 2 5 to 5 3 mm long and with a diameter of 3 7 mm) was used and investigated for photocatalytic degradation of textile dye effluent. A test system was built with a flat plate reactor(FPR) and UV light source(blacklight and solar simulator as light source respectively) for investigating the effectiveness of the new form of TiO 2. It was found that the photocatalytic process under this configuration could efficiently remove colours from textile dyeing effluent. Comparing with the TiO 2 powder, the pellet was very easy to recovered from the treated solution and can be reused in multiple times without the significant change on the photocatalytic property. The results also showed that to achieve the same photocatalytic performance, the FPR area by pellets was about 91% smaller than required by TiO 2 powder. At least TiO 2 pellet could be used as an alternative form of photocatalyst in applications for textile effluent treatment process, also other wastewater treatment processes.
基金financially supported by the Hubei Key Laboratory of Pollutant Analysis & Reuse Technology (No.KL2013M08)
文摘H3PW12O40/TiO2-SiO2 was synthesized by impregnation method which significantly improved the catalytic activity under simulated natural light. The prop- erties of the samples were characterized by Fourier trans- form infrared spectra （FTIR）, X-ray powder diffraction pattern （XRD）, Scanning electron micrographs （SEM）, and Zeta potential. Degradation of methyl violet was used as a probe reaction to explore the influencing factors on the photodegradation reaction. The results show that the opti- mal conditions are as follows： initial concentration of methyl violet of 10 mg·L^-1, pH of 3.0, catalyst dosage of 2.9 g·L^-1, and light irradiation time of 2.5 h. Under these conditions, the degradation rate of methyl violet is 95.4 %. The reaction on photodegradation for methyl violet can be expressed as the first-order kinetic model, and the possible mechanism for the photocatalysis under simulated natural light is suggested. After used continuously for five times, the catalyst keeps the inherent photocatalytic activity for degradation of dyes. The photodegradation of methyl orange, methyl red, naphthol green B, and methylene blue was also tested, and the degradation rate of dyes can reach 81%-100%.
基金supported by the Natural Science Foundation of China(22235001,22175020,22131005,22011540002,21631003)the Xiaomi Young Scholar Program+1 种基金the Fundamental Research Funds for the Central UniversitiesUniversity of Science and Technology Beijing
文摘Topochemical polymerization of molecular crystals into porous materials is of significance due to their promising applications in the field of adsorption and catalysis,yet rarely reported due to the synthesis difficulty.Herein,a hydrogen-bonded organic framework(HOF-45)has been fabricated by the crystallization of a cage-like building block containing three alkynyl groups.It exhibits almost mesoporous structure demonstrated by single crystal X-ray diffraction study.Light-driven topochemical polymerization of HOF-45 with ethanedithiol covalently links alkynyl groups in HOF-45,generating a hydrogen-bond and covalentbond cross-linked material(HOF-45C).In contrast to HOF-45,cross-linked HOF-45C retains the crystalline nature and displays improved solution resistence according to the powder X-ray diffraction data.In particular,HOF-45C is able to support the growth of ultrafine palladium nanoparticles with the average size of ca.1.9 nm for rapidly promoting the degradation of nitrophenol,methyl orange,and congo red with the help of NaBH_(4)as well as Suzuki-Miyaura coupling reaction.This work inputs a new idea on the HOFs application in preparing covalent-linked porous organic materials.
基金funded by the Science and Technology Development Fund (STDF), Ministry of Scientific Research (No. 1414, "Quantum Dots Nanomaterials Dye Sensitized Solar Cells")
文摘Highly active mesoporous TiO_2 of about 6 nm crystal size and 280.7 m^2/g specific surface areas has been successfully synthesized via controlled hydrolysis of titanium butoxide at acidic medium. It was characterized by means of XRD（X-ray diffraction）, SEM（scanning electron microscopy）, TEM（transmission electron microscopy）, FT-IR（Fourier transform infrared spectroscopy）, TGA（thermogravimetric analysis）, DSC（differential scanning calorimetry） and BET（Brunauer–Emmett–Teller） surface area. The degradation of dichlorophenol-indophenol（DCPIP） under ultraviolet（UV） light was studied to evaluate the photocatalytic activity of samples. The effects of different parameters and kinetics were investigated. Accordingly, a complete degradation of DCPIP dye was achieved by applying the optimal operational conditions of 1 g/L of catalyst, 10 mg/L of DCPIP, pH of 3 and the temperature at 25 ± 3°C after 3 min under UV irradiation. Meanwhile, the Langmuir–Hinshelwood kinetic model described the variations in pure photocatalytic branch in consistent with a first order power law model.The results proved that the prepared TiO_2 nanoparticle has a photocatalytic activity significantly better than Degussa P-25.
基金supported by the Ministry of Education,Science and Technological Development of the Republic of Serbia and the Slove-nian Research Agency (research core funding No. P2-0152)。
文摘Understanding the degradation behavior of azo dyes in photocatalytic wastewater treatment is of fundamental and practical importance for their application in textile-processing and other coloration industries. In this study, quantum chemistry, as density functional theory, was used to elucidate different degradation pathways of azo pyridone dyes in a hydroxyl radical(HO ·)-initiated photocatalytic system. A series of substituted azo pyridone dyes were synthesized by changing the substituent group in the para position of the benzene moiety, ranging from strong electron-donating to strong electron-withdrawing groups. The effect of dye molecular structure on the photocatalytic degradation reaction mechanism was analyzed and quantification of substituent effects on the thermodynamic and kinetics parameters was performed. Potential energy surface analysis revealed the most susceptible reaction site for the HO ·attack. The calculated reaction barriers are found to be strongly affected by the nature of substituent group with a good correlation using Hammett σp constants and experimentally determined reaction rates. The stability of pre-reaction complexes and transition state complexes were analyzed applying the distortion-interaction model. The increased stability of the transition state complexes with the distancing from the substituent group has been established.
基金the financial support provided by the National Natural Science Foundation of China(Nos.20934005 and 21274136)。
文摘Incautious discharge of organic dyes such as methyl orange(MO)has produced serious pollution to the environment,calling for the efficient techniques to remove them with retaining the green world.The photo-catalytic degradation of organic dyes is promising among the developed techniques.Thus,a strategy based on transpiration-prompted photocatalytic degradation of dye pollutant under sunlight is put forward.Aniline(ANI)is graft-polymerized onto poly(acrylamide-co-N-4-aminophenylacrylamide)(PAAm)cryogel embedded with gold nanoparticles(AuNPs,diameter:4-10 nm).The obtained cryogels integrated with AuNPs and PANI inside PAAm matrix(AuNP@PAAm-g-PANI)have been structurally explored based on the chemical composition and the phase/porous morphology.SEM and TEM observation shows that PANI and AuNPs are uniformly distributed in PAAm matrix.Since the macro-porosity of cryogel,hydrophilicity of PAAm and photo-thermal activity of PANI,PAAm-g-PANI cryogels without AuNPs can have a photo-thermal evaporation rate of water at 1.63 kg·m^(-2)·h^(-1).As a comparison,Au NP@PAAm-g-PANI cryogels with AuNPs exhibit higher one at 2.20 kg·m^(-2)·h^(-1),suggesting the promotion of AuNPs to photo-thermal evaporation.Meanwhile,PANI appreciatively assists AuNPs to display higher catalytic ability for the oxidative degradation of MO.Therefore,the removal of MO from water is obviously prompted by the water transpiration under sunlight with AuNP@PAAm-g-PANI cryogels,whose rate constant can reach to 0.320 h^(-1),being three folds of that for the sole absorption of MO.This transpiration-prompted photocatalytic degradation provides a fascinating route to eliminate organic pollutants and obtain pure water from wastewater simultaneously with sustainable sunlight energy.
