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2019 Volume 77 Issue 8
2019, 77(8): 681-689
doi: 10.6023/A19040118
Abstract:
Covalent organic frameworks (COFs) are a class of porous crystalline materials consisting of organic units connected through covalent bonds. Due to their low density, high surface area and high thermal stability, COFs have found interesting applications in many fields, including molecular adsorption and separation, sensing, catalysis and optoelectronics devices. In particular, two-dimensional (2D) COFs have attracted increasing attention in energy fields. In this perspective, the applications of 2D COFs in energy storage (lithium ion batteries, lithium-sulfur batteries, supercapacitor and fuel cells) and energy conversion (water splitting and reduction of carbon dioxide) are reviewed. In addition, we will also discuss the remaining challenging issues.
Covalent organic frameworks (COFs) are a class of porous crystalline materials consisting of organic units connected through covalent bonds. Due to their low density, high surface area and high thermal stability, COFs have found interesting applications in many fields, including molecular adsorption and separation, sensing, catalysis and optoelectronics devices. In particular, two-dimensional (2D) COFs have attracted increasing attention in energy fields. In this perspective, the applications of 2D COFs in energy storage (lithium ion batteries, lithium-sulfur batteries, supercapacitor and fuel cells) and energy conversion (water splitting and reduction of carbon dioxide) are reviewed. In addition, we will also discuss the remaining challenging issues.
2019, 77(8): 690-704
doi: 10.6023/A19060222
Abstract:
Axial chirality is of significant importance in chiral molecules. Axially chiral biaryls are existed in numerous natural products and biologically active molecules. Moreover, they have been extensively used as chiral catalysts and chiral ligands in asymmetric catalysis. Due to the importance of these privileged scaffolds, considerable attention has been attracted to develop novel, efficient and practical methods for their asymmetric synthesis by utilizing chiral transition-metal catalysis or chiral organocatalysis. Among those reported elegant achievements, asymmetric C—H bond functionalization reactions are the most concise and efficient methods for the synthesis of axial chiral biaryls in terms of atom and step economies. With the advancement of transition-metal-catalyzed asymmetric C—H bond functionalization reactions, they largely promote the field of asymmetric synthesis of axially chiral biaryls. Recent progress on the development of synthesis of axially chiral biaryls via transition metal (Pd-, Rh-, and Ir-) catalyzed asymmetric C—H bond functionalization reactions are summarized in this review. Those mainly include:Rh-catalyzed enantioselective C(sp2)-H bond alkylation and arylation reactions with the combination of rhodium (I) catalyst precursors and chiral phosphine ligands; Rh-catalyzed enantioselective C(sp2)-H bond alkenylation, arylation and annulation reactions with well-defined chiral rhodium (Ⅲ)-Cp(SCp) complexes; Ir-catalyzed enantioselective C(sp2)-H bond arylation reactions with chiral iridium (Ⅲ)-Cp complex and chiral amino acid as co-catalyst; Pd-catalyzed diastereoselective C(sp2)-H bond alkenylation, iodination, and arylation reactions using chiral p-tolyl sulfoxide auxiliary or menthyl phenylphosphate group as a directing group; Pd-catalyzed intramolecular enantioselective C(sp2)-H bond arylation reaction with Pd(0) catalyst precursors and chiral TADDOL-phosphoramidites; Pd-catalyzed intermolecular enantioselective C(sp2)-H bond iodination, alkenylation, alkynylation, allylation and arylation reactions with Pd(Ⅱ) catalyst precursors and mono-N-protected amino acids (MPAAs). In addition, preparation of varieties of novel axially chiral ligands by utilizing these methods and their applications in catalytic asymmetric reactions are also covered. Meanwhile, applications of these methods as key steps in the synthesis of natural products are also discussed.
Axial chirality is of significant importance in chiral molecules. Axially chiral biaryls are existed in numerous natural products and biologically active molecules. Moreover, they have been extensively used as chiral catalysts and chiral ligands in asymmetric catalysis. Due to the importance of these privileged scaffolds, considerable attention has been attracted to develop novel, efficient and practical methods for their asymmetric synthesis by utilizing chiral transition-metal catalysis or chiral organocatalysis. Among those reported elegant achievements, asymmetric C—H bond functionalization reactions are the most concise and efficient methods for the synthesis of axial chiral biaryls in terms of atom and step economies. With the advancement of transition-metal-catalyzed asymmetric C—H bond functionalization reactions, they largely promote the field of asymmetric synthesis of axially chiral biaryls. Recent progress on the development of synthesis of axially chiral biaryls via transition metal (Pd-, Rh-, and Ir-) catalyzed asymmetric C—H bond functionalization reactions are summarized in this review. Those mainly include:Rh-catalyzed enantioselective C(sp2)-H bond alkylation and arylation reactions with the combination of rhodium (I) catalyst precursors and chiral phosphine ligands; Rh-catalyzed enantioselective C(sp2)-H bond alkenylation, arylation and annulation reactions with well-defined chiral rhodium (Ⅲ)-Cp(SCp) complexes; Ir-catalyzed enantioselective C(sp2)-H bond arylation reactions with chiral iridium (Ⅲ)-Cp complex and chiral amino acid as co-catalyst; Pd-catalyzed diastereoselective C(sp2)-H bond alkenylation, iodination, and arylation reactions using chiral p-tolyl sulfoxide auxiliary or menthyl phenylphosphate group as a directing group; Pd-catalyzed intramolecular enantioselective C(sp2)-H bond arylation reaction with Pd(0) catalyst precursors and chiral TADDOL-phosphoramidites; Pd-catalyzed intermolecular enantioselective C(sp2)-H bond iodination, alkenylation, alkynylation, allylation and arylation reactions with Pd(Ⅱ) catalyst precursors and mono-N-protected amino acids (MPAAs). In addition, preparation of varieties of novel axially chiral ligands by utilizing these methods and their applications in catalytic asymmetric reactions are also covered. Meanwhile, applications of these methods as key steps in the synthesis of natural products are also discussed.
2019, 77(8): 705-716
doi: 10.6023/A19030073
Abstract:
The total discharge of Chinese industrial wastewater is large, and the various organic pollutants contained in wastewater have always been a potential threat to human health. Therefore, it is necessary to develop various technologies for wastewater treatment, especially to study the degradation mechanism of organic pollutants. This paper summarizes the research methods for the degradation mechanism of various organic pollutants in wastewater, including experimental methods and computational simulations. In the experiments, spectral analysis techniques are mainly used to detect the intermediates produced during the degradation of organic pollutants, and then the degradation pathways of organic pollutants are deduced. However, due to the different experimental conditions and experimental methods, the degradation pathways of the same pollutant obtained from the different experiments are controversial. Computational simulations, based on the quantum chemical calculation, quantitative structure-activity relationship model, quantitative structure-biodegradation relationship model and statistical molecular fragmentation model, provide a new method for studying the degradation mechanism of organic pollutants. The combination of experimental methods and computational simulations will provide the foundation and guidance for exploring the degradation mechanism of organic pollutants.
The total discharge of Chinese industrial wastewater is large, and the various organic pollutants contained in wastewater have always been a potential threat to human health. Therefore, it is necessary to develop various technologies for wastewater treatment, especially to study the degradation mechanism of organic pollutants. This paper summarizes the research methods for the degradation mechanism of various organic pollutants in wastewater, including experimental methods and computational simulations. In the experiments, spectral analysis techniques are mainly used to detect the intermediates produced during the degradation of organic pollutants, and then the degradation pathways of organic pollutants are deduced. However, due to the different experimental conditions and experimental methods, the degradation pathways of the same pollutant obtained from the different experiments are controversial. Computational simulations, based on the quantum chemical calculation, quantitative structure-activity relationship model, quantitative structure-biodegradation relationship model and statistical molecular fragmentation model, provide a new method for studying the degradation mechanism of organic pollutants. The combination of experimental methods and computational simulations will provide the foundation and guidance for exploring the degradation mechanism of organic pollutants.
2019, 77(8): 717-728
doi: 10.6023/A19050185
Abstract:
Water is the most important and essential component for the existing activities of human beings, animals and plants. It is estimated that the total amount of water on the earth is about 1.3 billion tons, but 97% of that is salty ocean water and not suitable for drinking. With the rapid growth of population, industrialization and agricultural modernization and other geological and environmental changes, the water environment is deteriorating continuously. Water pollution and water shortage are two of the most important environmental problems in the world. Consequently, water pollution has become a critical issue in recent years. Pollutants in wastewater include organic, inorganic, biological compounds. As many of them have serious toxicity and even show carcinogenic, the release of considerable amount of wastewater into environment causes damages to human being and aquatic conditions, and further leads to the shortage of water resources. Therefore, the need for wastewater treatment in a low-cost, safe and efficient way and improving the reuse efficiency of water resources have become a must. In recent years, surfactant-based separation techniques have made a great progress in industrial and analytical areas. It offers many advantages including low-energy consumption and environment protection, and has been proved efficient in the separation of many inorganic and organic pollutants. To enhance the application of surfactant-based separation techniques in wastewater treatment, it is very important to have a better understanding of the mechanisms involved in this process. The mechanism and development of surfactant-based wastewater treatment techniques, including micelle-enhanced ultrafiltration (MEUF), surfactant-modified solid phase adsorption and surfactant-based liquid-liquid phase separation are summarized. The effects of the surfactant characteristics, the chemistry of the pollutants and the solution conditions used in experiments on the extract kinetics and efficiencies are discussed. This review aims to provide reference and inspiration for researchers and promote the development of wastewater treatment technologies.
Water is the most important and essential component for the existing activities of human beings, animals and plants. It is estimated that the total amount of water on the earth is about 1.3 billion tons, but 97% of that is salty ocean water and not suitable for drinking. With the rapid growth of population, industrialization and agricultural modernization and other geological and environmental changes, the water environment is deteriorating continuously. Water pollution and water shortage are two of the most important environmental problems in the world. Consequently, water pollution has become a critical issue in recent years. Pollutants in wastewater include organic, inorganic, biological compounds. As many of them have serious toxicity and even show carcinogenic, the release of considerable amount of wastewater into environment causes damages to human being and aquatic conditions, and further leads to the shortage of water resources. Therefore, the need for wastewater treatment in a low-cost, safe and efficient way and improving the reuse efficiency of water resources have become a must. In recent years, surfactant-based separation techniques have made a great progress in industrial and analytical areas. It offers many advantages including low-energy consumption and environment protection, and has been proved efficient in the separation of many inorganic and organic pollutants. To enhance the application of surfactant-based separation techniques in wastewater treatment, it is very important to have a better understanding of the mechanisms involved in this process. The mechanism and development of surfactant-based wastewater treatment techniques, including micelle-enhanced ultrafiltration (MEUF), surfactant-modified solid phase adsorption and surfactant-based liquid-liquid phase separation are summarized. The effects of the surfactant characteristics, the chemistry of the pollutants and the solution conditions used in experiments on the extract kinetics and efficiencies are discussed. This review aims to provide reference and inspiration for researchers and promote the development of wastewater treatment technologies.
2019, 77(8): 729-734
doi: 10.6023/A19050190
Abstract:
Transition metal-catalyzed C—H activation has attracted extensive attention because of its excellent functional group tolerance and high efficiency. Among them, palladium-catalyzed reactions exhibit versatile catalytic cycles and have mild conditions compared to others. Therefore, the palladium-catalyzed C—H activation has been employed broadly as a practical strategy in synthetic chemistry during the past decade. Since the first example of palladium-catalyzed decarboxylative C—H acylation using α-oxocarboxylic acids was reported in 2008, a lot of substrates have been employed to synthesize acylated products due to the easily available α-oxocarboxylic acids as well as the importance of acylation. However, the transition metal-catalyzed C—H esterification via decarbonylation is still limited. Our group previously developed the first directed C—H esterification of methyl ketoximes and 2-phenylpyridines by using potassium oxalate monoester as the decarboxylative reagent. Encouraged by this impressive result as well as the importance of salicylate derivatives in drug discovery, herein we disclose the efficient palladium-catalyzed decarboxylative esterification of 2-aryloxpyridines. This reaction proceeds smoothly with potassium oxalate monoester, affording the desired products in moderate to good yields (50%~82%). Compared to our previous work, the electron-donating pyridinyloxy (PyO) group as the directing group and six-membered metallocycle intermediate dramatically enhance the practicability and substrate tolerance of the present method. In addition, one of the products has been chosen as the model compound to deprotect the directing group to get the valuable salicylate derivative. The present method not only provides an efficient and convenient protocol for the synthesis of ethyl salicylate derivatives, but also enriches the diversity of Pd(Ⅱ)/Pd(Ⅳ) catalytic reactions. A general procedure for the esterification of 2-aryloxypyridines 1 with potassium oxalate monoester 2 is as following:a mixture of 1 (0.5 mmol), Pd(OAc)2 (10 mol%), K2S2O8 (1.0 mmol), Ag2CO3 (1.0 mmol), 2 (1.0 mmol), D-CSA (0.125 mmol), and 1, 4-dioxane (2.5 mL) in a 25 mL tube was heated at 80℃ for a suitable time. The reaction mixture was cooled to room temperature, and concentrated in vacuo. Purification of the residue by column chromatography on silica gel with petroleum ether and ethyl acetate as the eluent provided the desired product 3.
Transition metal-catalyzed C—H activation has attracted extensive attention because of its excellent functional group tolerance and high efficiency. Among them, palladium-catalyzed reactions exhibit versatile catalytic cycles and have mild conditions compared to others. Therefore, the palladium-catalyzed C—H activation has been employed broadly as a practical strategy in synthetic chemistry during the past decade. Since the first example of palladium-catalyzed decarboxylative C—H acylation using α-oxocarboxylic acids was reported in 2008, a lot of substrates have been employed to synthesize acylated products due to the easily available α-oxocarboxylic acids as well as the importance of acylation. However, the transition metal-catalyzed C—H esterification via decarbonylation is still limited. Our group previously developed the first directed C—H esterification of methyl ketoximes and 2-phenylpyridines by using potassium oxalate monoester as the decarboxylative reagent. Encouraged by this impressive result as well as the importance of salicylate derivatives in drug discovery, herein we disclose the efficient palladium-catalyzed decarboxylative esterification of 2-aryloxpyridines. This reaction proceeds smoothly with potassium oxalate monoester, affording the desired products in moderate to good yields (50%~82%). Compared to our previous work, the electron-donating pyridinyloxy (PyO) group as the directing group and six-membered metallocycle intermediate dramatically enhance the practicability and substrate tolerance of the present method. In addition, one of the products has been chosen as the model compound to deprotect the directing group to get the valuable salicylate derivative. The present method not only provides an efficient and convenient protocol for the synthesis of ethyl salicylate derivatives, but also enriches the diversity of Pd(Ⅱ)/Pd(Ⅳ) catalytic reactions. A general procedure for the esterification of 2-aryloxypyridines 1 with potassium oxalate monoester 2 is as following:a mixture of 1 (0.5 mmol), Pd(OAc)2 (10 mol%), K2S2O8 (1.0 mmol), Ag2CO3 (1.0 mmol), 2 (1.0 mmol), D-CSA (0.125 mmol), and 1, 4-dioxane (2.5 mL) in a 25 mL tube was heated at 80℃ for a suitable time. The reaction mixture was cooled to room temperature, and concentrated in vacuo. Purification of the residue by column chromatography on silica gel with petroleum ether and ethyl acetate as the eluent provided the desired product 3.
2019, 77(8): 735-740
doi: 10.6023/A19060214
Abstract:
Cucurbit[8]uril (CB[8])-encapsulation-based host-guest chemistry has been utilized to construct supramolecular organic frameworks, a family of water-soluble, self-assembled periodic porous structures, from multi-armed preorganized building blocks. The tetrahedral prototype building block has been incorporated with four CH2 units to connect the central tetraphenylmethane and appended aromatic arms. Herein we designed and prepared a new fully conjugated tetrahedral building block T-1, which possesses four N-methyl 4-(4-styrylphenyl)pyridinium (SPP) arms. The 1:2 mixture of T-1 with CB[8] in water leads to the formation of a new three-dimensional homogeneous diamondoid supramolecular organic framework SOF-r-SPP through CB[8] encapsulation for intermolecular dimers of the appended SPP units. 1H NMR, absorption and fluorescence experiments conformed strong binding between the two components at diluted concentrations and 1:2 binding stoichiometry. Isothermal calorimetric (ITC) experiments established that the three-component (SPP)2ÌCB[8] complexes formed between the SPP units of T-1 and CB[8] had an apparent binding constant of 5.5×1013 M-2, which was 5.5×104 times as high as that of the complex of a SPP control. ITC experiments also revealed that the self-assembly of SOF-r-SPP are driven both enthalpically and entropically, but the enthalpic contribution was overwhelmingly higher. Dynamic light scattering experiments revealed that within the concentration range of 0.031 mmol/L to 1.0 mmol/L of T-1, the framework possessed a hydrodynamic diameter of 41 nm to 68 nm. Molecular modelling study indicated that the new regular framework formed an aperture of 2.3 nm. Although T-1 has nearly no fluorescence, SOF-r-SPP exhibits strong fluorescence in water probably due to the encapsulation of the SPP dimers by CB[8] that suppresses the relative rotation of the aromatic rings. Adding nitrobenzene or naphthalene derivatives to the solution of SOF-r-SPP remarkably quenched the fluorescence of the framework. Among other sixteen nitro-bearing aromatic molecules, picric acid (2, 4, 6-trinitrophenol) exhibited the largest quenching ability. At the low concentration of 1.0 μmol/L for T-1 of SOF-r-SPP, 0.1 μmol/L of 2, 4, 6-tirnitrophenol could cause 16% quenching of the fluorescence of SOF-r-SPP and 0.1 mmol/L of 2, 4, 6-tirnitrophenol could realize nearly complete quench (>97%). Following a reported method, the limit of detection of SOF-r-SPP for picric acid was as low as 0.024 μmol/L.
Cucurbit[8]uril (CB[8])-encapsulation-based host-guest chemistry has been utilized to construct supramolecular organic frameworks, a family of water-soluble, self-assembled periodic porous structures, from multi-armed preorganized building blocks. The tetrahedral prototype building block has been incorporated with four CH2 units to connect the central tetraphenylmethane and appended aromatic arms. Herein we designed and prepared a new fully conjugated tetrahedral building block T-1, which possesses four N-methyl 4-(4-styrylphenyl)pyridinium (SPP) arms. The 1:2 mixture of T-1 with CB[8] in water leads to the formation of a new three-dimensional homogeneous diamondoid supramolecular organic framework SOF-r-SPP through CB[8] encapsulation for intermolecular dimers of the appended SPP units. 1H NMR, absorption and fluorescence experiments conformed strong binding between the two components at diluted concentrations and 1:2 binding stoichiometry. Isothermal calorimetric (ITC) experiments established that the three-component (SPP)2ÌCB[8] complexes formed between the SPP units of T-1 and CB[8] had an apparent binding constant of 5.5×1013 M-2, which was 5.5×104 times as high as that of the complex of a SPP control. ITC experiments also revealed that the self-assembly of SOF-r-SPP are driven both enthalpically and entropically, but the enthalpic contribution was overwhelmingly higher. Dynamic light scattering experiments revealed that within the concentration range of 0.031 mmol/L to 1.0 mmol/L of T-1, the framework possessed a hydrodynamic diameter of 41 nm to 68 nm. Molecular modelling study indicated that the new regular framework formed an aperture of 2.3 nm. Although T-1 has nearly no fluorescence, SOF-r-SPP exhibits strong fluorescence in water probably due to the encapsulation of the SPP dimers by CB[8] that suppresses the relative rotation of the aromatic rings. Adding nitrobenzene or naphthalene derivatives to the solution of SOF-r-SPP remarkably quenched the fluorescence of the framework. Among other sixteen nitro-bearing aromatic molecules, picric acid (2, 4, 6-trinitrophenol) exhibited the largest quenching ability. At the low concentration of 1.0 μmol/L for T-1 of SOF-r-SPP, 0.1 μmol/L of 2, 4, 6-tirnitrophenol could cause 16% quenching of the fluorescence of SOF-r-SPP and 0.1 mmol/L of 2, 4, 6-tirnitrophenol could realize nearly complete quench (>97%). Following a reported method, the limit of detection of SOF-r-SPP for picric acid was as low as 0.024 μmol/L.
2019, 77(8): 741-750
doi: 10.6023/A19060200
Abstract:
Perovskite solar cells (PVSCs) have recently gained much attention for the advantages of low cost and high efficiency. Based on the different device structures, PVSCs can be simply classified into conventional and inverted categories. Compared with the inverted devices, conventional PVSCs generally exhibited higher PCE. Especially, a milestone PCE value of 24.3% was obtained in conventional PVSCs. However, the complexity and high-temperature process in device fabrication further limit their application in flexible and large-scale devices, while the inverted PVSCs can make up the shortcomings of the conventional PVSCs. Commonly, PVSCs devices contain electrodes, electron/hole transporting layers and the perovskite layer. Among the function layers, hole transporting layers (HTLs) play a crucial role in improving the photovoltaic performance of inverted PVSCs. From the materials point of view, the efficient hole transporting materials (HTMs) are mostly inorganic compounds and polymers. On the other side, taking advantages of easy modification, low price, easy preparation and homogeneity in batches, small molecular HTMs afford superior promising in fabricating efficient and stable PVSCs. However, up to date, small molecular HTMs are relatively less explored. To enrich the material species of small molecular HTMs and illustrate their superiorities in constructing stable PVSCs, in this paper, we designed and synthesized three D-π-A-π-D type small molecular HTMs based on triphenylamine (TPA) unit, namely 1-T, 1-OT and 1-OTCN. The optoelectronic properties of these molecules were modified by introducing different electron acceptor/donor groups. Afterwards, employing as dopant-free HTMs in inverted PVSCs, the three small molecules demonstrated distinguished performance. We found that introduction of electron-donating methoxy into 1-T, 1-OT exhibited increased energy levels and hole mobility. On the other hand, the energy levels of 1-OTCN were down-shifted compared to 1-OT, which was attributed from the stronger electron-withdrawing ability of dicyanovinylene group than carbonyl group. Among the devices with new HTMs, 1-OTCN based PVSCs achieved the best PCE of 16.8%, with open-circuit voltage (VOC) of 1.09 V, short-circuit current density (JSC) of 20.13 mA·cm-2 and fill factor (FF) of 78%. Compared with other HTMs, the higher JSC of 1-OTCN based PVSCs was ascribed from more efficient charge transfer and extraction in the interface of HTL/perovskite. Moreover, in contrast with the hydrophilicity of PEDOT:PSS, the hydrophobicity of 1-OTCN contributed to the satisfactory stability of PVSCs.
Perovskite solar cells (PVSCs) have recently gained much attention for the advantages of low cost and high efficiency. Based on the different device structures, PVSCs can be simply classified into conventional and inverted categories. Compared with the inverted devices, conventional PVSCs generally exhibited higher PCE. Especially, a milestone PCE value of 24.3% was obtained in conventional PVSCs. However, the complexity and high-temperature process in device fabrication further limit their application in flexible and large-scale devices, while the inverted PVSCs can make up the shortcomings of the conventional PVSCs. Commonly, PVSCs devices contain electrodes, electron/hole transporting layers and the perovskite layer. Among the function layers, hole transporting layers (HTLs) play a crucial role in improving the photovoltaic performance of inverted PVSCs. From the materials point of view, the efficient hole transporting materials (HTMs) are mostly inorganic compounds and polymers. On the other side, taking advantages of easy modification, low price, easy preparation and homogeneity in batches, small molecular HTMs afford superior promising in fabricating efficient and stable PVSCs. However, up to date, small molecular HTMs are relatively less explored. To enrich the material species of small molecular HTMs and illustrate their superiorities in constructing stable PVSCs, in this paper, we designed and synthesized three D-π-A-π-D type small molecular HTMs based on triphenylamine (TPA) unit, namely 1-T, 1-OT and 1-OTCN. The optoelectronic properties of these molecules were modified by introducing different electron acceptor/donor groups. Afterwards, employing as dopant-free HTMs in inverted PVSCs, the three small molecules demonstrated distinguished performance. We found that introduction of electron-donating methoxy into 1-T, 1-OT exhibited increased energy levels and hole mobility. On the other hand, the energy levels of 1-OTCN were down-shifted compared to 1-OT, which was attributed from the stronger electron-withdrawing ability of dicyanovinylene group than carbonyl group. Among the devices with new HTMs, 1-OTCN based PVSCs achieved the best PCE of 16.8%, with open-circuit voltage (VOC) of 1.09 V, short-circuit current density (JSC) of 20.13 mA·cm-2 and fill factor (FF) of 78%. Compared with other HTMs, the higher JSC of 1-OTCN based PVSCs was ascribed from more efficient charge transfer and extraction in the interface of HTL/perovskite. Moreover, in contrast with the hydrophilicity of PEDOT:PSS, the hydrophobicity of 1-OTCN contributed to the satisfactory stability of PVSCs.
2019, 77(8): 751-757
doi: 10.6023/A19040109
Abstract:
In this paper, the intermediates 2'-hydroxybiphenyl-2-amine (I1) and 2'-methoxybiphenyl-2-amine (I2) were first synthetized via Suzuki reaction of 2-bromoaniline and arylboronic acid under 80℃. Meanwhile, organic dyes benzidine fragments ((E)-2'-(2-nitrobenzylideneamino)-biphenyl-3-ol (C1) and (E)-2'-(2, 4-dinitrobenzylideneamino)-biphenyl-3-ol (C3)) which could undergo intermolecular proton transfer in excited states were synthetized via aminoaldehyde condensation of the intermediates biphenyl-2-amine and corresponding aldehyde. In addition, the dyes without proton transfer segments ((E)-2'-methoxy-N-(2-nitrobenzylidene)biphenyl-3-amine (C2) and (E)-2'-methoxy-N-(2, 4-dinitrobenzylidene)biphenyl-3-amine (C4)) were also synthesized to act as references for comparisons experiment. The chemical structures of organic dyes were characterized by nuclear magnetic resonance (NMR) spectra, infrared spectra (IR), high resolution mass spectrometry (HR-MS) as well as elemental analysis. The analysis of X-ray single crystal diffraction and H NMR spectra suggest the presence of internal hydrogen bond with different strength in the target dyes C1 and C3. It indicated that the type of substituents has an effect on the chemical shift of hydroxyl groups, with the electron-withdrawing ability of substituents increases, the hydroxyl shift to higher field. Then the UV/visible spectra also confirm that the target dyes have intermolecular hydrogen bond, while there is no intermolecular hydrogen bond in the reference dyes C2 and C4. The excited-state intermolecular proton transfer (ESPT) properties of the organic dyes were further studied by fluorescence emission spectroscopy. It was found that target dye C3 could occur excited state intermolecular proton transfer (ESPT) via intermolecular hydrogen bonding in non-protonic solvents. In contrast, ESPT properties cannot be processed through hydrogen-bonding interaction of the studied target dye C1 no matter in protonic solvents, non-protonic solvents or in solid state. The target dye C1 and reference dyes (C2 and C4) only show the normal fluorescence emission peaks. It was worth mentioning that with the increasing concentration of C3 in solution, the ESPT reaction ability could be enhanced. Meanwhile, C3 can also occurs ESPT in solid state.
In this paper, the intermediates 2'-hydroxybiphenyl-2-amine (I1) and 2'-methoxybiphenyl-2-amine (I2) were first synthetized via Suzuki reaction of 2-bromoaniline and arylboronic acid under 80℃. Meanwhile, organic dyes benzidine fragments ((E)-2'-(2-nitrobenzylideneamino)-biphenyl-3-ol (C1) and (E)-2'-(2, 4-dinitrobenzylideneamino)-biphenyl-3-ol (C3)) which could undergo intermolecular proton transfer in excited states were synthetized via aminoaldehyde condensation of the intermediates biphenyl-2-amine and corresponding aldehyde. In addition, the dyes without proton transfer segments ((E)-2'-methoxy-N-(2-nitrobenzylidene)biphenyl-3-amine (C2) and (E)-2'-methoxy-N-(2, 4-dinitrobenzylidene)biphenyl-3-amine (C4)) were also synthesized to act as references for comparisons experiment. The chemical structures of organic dyes were characterized by nuclear magnetic resonance (NMR) spectra, infrared spectra (IR), high resolution mass spectrometry (HR-MS) as well as elemental analysis. The analysis of X-ray single crystal diffraction and H NMR spectra suggest the presence of internal hydrogen bond with different strength in the target dyes C1 and C3. It indicated that the type of substituents has an effect on the chemical shift of hydroxyl groups, with the electron-withdrawing ability of substituents increases, the hydroxyl shift to higher field. Then the UV/visible spectra also confirm that the target dyes have intermolecular hydrogen bond, while there is no intermolecular hydrogen bond in the reference dyes C2 and C4. The excited-state intermolecular proton transfer (ESPT) properties of the organic dyes were further studied by fluorescence emission spectroscopy. It was found that target dye C3 could occur excited state intermolecular proton transfer (ESPT) via intermolecular hydrogen bonding in non-protonic solvents. In contrast, ESPT properties cannot be processed through hydrogen-bonding interaction of the studied target dye C1 no matter in protonic solvents, non-protonic solvents or in solid state. The target dye C1 and reference dyes (C2 and C4) only show the normal fluorescence emission peaks. It was worth mentioning that with the increasing concentration of C3 in solution, the ESPT reaction ability could be enhanced. Meanwhile, C3 can also occurs ESPT in solid state.
2019, 77(8): 758-764
doi: 10.6023/A19040129
Abstract:
A series of bimetallic MOF-74-CoMn catalysts with different metal ratios have been successfully synthesized by hydrothermal method and applied in selective catalytic reduction of NO with CO (CO-SCR). The experimental procedure for the preparation of MOF-74-CoMn catalyst is as follows:The reaction solution was a 3.28 mmol mixture of Co(NO3)2·6H2O and Mn(NO3)2·6H2O, 1.09 mmol 2, 5-dihydroxyterephthalic acid (H4DOBDC) and 90 mL ethanol-DMF-water. The molar ratio of mixture (Co/Mn) was 1:0, 1:1, 1:2, 1:4, 1:6, respectively. The reactant solution was ultrasonically stired for 30 min until homogeneous. Then, the mixture was transferred into a 100 mL Teflon autoclave then kept in an oven at 100℃ for 24 h. Finally, after purified with DMF and methanol, the products were dried in a vacuum oven at 80℃ for 24 h to obtain a purple MOF-74-CoMn catalyst, which were stored in vacuum or an inert atmosphere. The prepared sample is referred to as MOF-74-Co1Mnx, where x represents a molar ratio of Co to Mn is 1:x (x=0, 1, 2, 4, 6). The SCR catalytic activities were carried out in a fixed-bed flow reactor in gas stream. The experimental results show that the NOx conversion rate of bimetallic MOF-74-CoMn catalyst is generally higher than that of single metal MOF-74-Co catalyst, and their reaction temperature window is wider. Especially, MOF-74-Co1Mn2 exhibited the highest selective catalytic reduction of NO with CO (CO-SCR) performance which is close to 100% with a temperature range from 175 to 275℃. Further, the bimetallic MOFs catalysts were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), N2 adsorption/desorption, X-ray photoelectron spectroscopy (XPS), Hydrogen-temperature programed reduction (H2-TPR) and Infrared spectroscopy (FTIR) techniques. The results showed that the synergistic effect between Co and Mn metals could obviously promote the formation of unsaturated metal sites and oxygen vacancies, thereby promoting their catalytic reduction efficiency of selective catalytic reduction of NO with CO (CO-SCR).
A series of bimetallic MOF-74-CoMn catalysts with different metal ratios have been successfully synthesized by hydrothermal method and applied in selective catalytic reduction of NO with CO (CO-SCR). The experimental procedure for the preparation of MOF-74-CoMn catalyst is as follows:The reaction solution was a 3.28 mmol mixture of Co(NO3)2·6H2O and Mn(NO3)2·6H2O, 1.09 mmol 2, 5-dihydroxyterephthalic acid (H4DOBDC) and 90 mL ethanol-DMF-water. The molar ratio of mixture (Co/Mn) was 1:0, 1:1, 1:2, 1:4, 1:6, respectively. The reactant solution was ultrasonically stired for 30 min until homogeneous. Then, the mixture was transferred into a 100 mL Teflon autoclave then kept in an oven at 100℃ for 24 h. Finally, after purified with DMF and methanol, the products were dried in a vacuum oven at 80℃ for 24 h to obtain a purple MOF-74-CoMn catalyst, which were stored in vacuum or an inert atmosphere. The prepared sample is referred to as MOF-74-Co1Mnx, where x represents a molar ratio of Co to Mn is 1:x (x=0, 1, 2, 4, 6). The SCR catalytic activities were carried out in a fixed-bed flow reactor in gas stream. The experimental results show that the NOx conversion rate of bimetallic MOF-74-CoMn catalyst is generally higher than that of single metal MOF-74-Co catalyst, and their reaction temperature window is wider. Especially, MOF-74-Co1Mn2 exhibited the highest selective catalytic reduction of NO with CO (CO-SCR) performance which is close to 100% with a temperature range from 175 to 275℃. Further, the bimetallic MOFs catalysts were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), N2 adsorption/desorption, X-ray photoelectron spectroscopy (XPS), Hydrogen-temperature programed reduction (H2-TPR) and Infrared spectroscopy (FTIR) techniques. The results showed that the synergistic effect between Co and Mn metals could obviously promote the formation of unsaturated metal sites and oxygen vacancies, thereby promoting their catalytic reduction efficiency of selective catalytic reduction of NO with CO (CO-SCR).
