The metal contents of Nigerian coal minerals were analyzed using an atomic absorption spectrophotometer. Calcium, Na, and Fe occurred as the major elements with concentrations ranging from 9 782 μg/g for Ca to 432 μ...The metal contents of Nigerian coal minerals were analyzed using an atomic absorption spectrophotometer. Calcium, Na, and Fe occurred as the major elements with concentrations ranging from 9 782 μg/g for Ca to 432 μg/g for Na whereas K, Mg, Mn, Ni, Cr, Zn, Pb, and Cu, which occurred at trace levels ranged from 673.73 μg/g for Mg to 2.97 μg/g for Mn. The results of the quantitative analysis of porphyrins extracted from the coal minerals showed that Onyeama coal has the highest amount of porphyrins (ca～0.96 μg/g) while Okpara has the lowest (ca～0.30 μg/g). The porphyrins were qualitatively characterized by a combination of thin layer chromatography (TLC), infrared, and ultraviolet-visible spectrophotometers. The results of the mid infrared analysis (MIR) showed the presence of absorption bands at 3 440 cm～1～3 450 cm-1 and 1 640 cm-1～1 680 cm-1 , which are owing to the stretching vibrations of N ─ H and C─ C of aromatics, with C─ H out of plane (oop) bending vibrations at wavenumbers less than 900 cm-1, all of which are characteristic absorptions of porphyrin free base. The ultraviolet-visible data showed prominent peaks at ～400 nm(Soret band) and at wavelength ranges of 535 nm～550 nm(β-band) and 565 nm～ 600 nm (α-band) for the coal porphyrins analyzed. The geochemical significance of the metals and porphyrins in coal minerals are discussed.展开更多
Efficiently converting CO_(2)and H_(2)O into value-added chemicals using solar energy is a viable approach to address global warming and the energy crisis.However,achieving artificial photocatalytic CO_(2)reduction us...Efficiently converting CO_(2)and H_(2)O into value-added chemicals using solar energy is a viable approach to address global warming and the energy crisis.However,achieving artificial photocatalytic CO_(2)reduction using H_(2)O as the reductant poses challenges is due to the difficulty in efficient cooperation among multiple functional moieties.Metal-organic frameworks(MOFs)are promising candidates for overall CO_(2)photoreduction due to their large surface area,diverse active sites,and excellent tailorability.In this study,we designed a metal-organic framework photocatalyst,named PCN-224(Zn)-Bpy(Ru),by integrating photoactive Zn(Ⅱ)-porphyrin and Ru(Ⅱ)-bipyridyl moieties.In comparison,two isostructural MOFs just with either Zn(Ⅱ)-porphyrin or Ru(Ⅱ)-bipyridyl moiety,namely PCN-224-Bpy(Ru)and PCN-224(Zn)-Bpy were also synthesized.As a result,PCN-224(Zn)-Bpy(Ru)exhibited the highest photocatalytic conversion rate of CO_(2)to CO,with a production rate of 7.6μmol·g^(-1)·h^(-1)in a mixed solvent of CH_(3)CN and H_(2)O,without the need for co-catalysts,photosensitizers,or sacrificial agents.Mass spectrometer analysis detected the signals of^(13)CO(m/z=29),^(13)C^(18)O(m/z=31),^(16)O^(18)O(m/z=34),and^(18)O_(2)(m/z=36),confirming that CO_(2)and H_(2)O acted as the carbon and oxygen sources for CO and O_(2),respectively,thereby confirming the coupling of photocatalytic CO_(2)reduction with H_(2)O oxidation.In contrast,using PCN-224-Bpy(Ru)or PCN-224(Zn)-Bpy as catalysts under the same conditions resulted in significantly lower CO production rates of only 1.5 and 0μmol·g^(-1)·h^(-1),respectively.Mechanistic studies revealed that the lowest unoccupied molecular orbital(LUMO)potential of PCN-224(Zn)-Bpy(Ru)is more negative than the redox potentials of CO_(2)/CO,and the highest occupied molecular orbital(HOMO)potential is more positive than that of H_(2)O/O_(2),satisfying the thermodynamic requirements for overall photocatalytic CO_(2)reduction.In comparison,the HOMO potential of PCN-224(Zn)-Bpy without Ru(II)-bipyridyl moieties is less positive than that of H_(2)O/O_(2),indicating that the Ru(II)-bipyridyl moiety is thermodynamically necessary for CO_(2)reduction coupled with H_(2)O oxidation.Additionally,photoluminescence spectroscopy revealed that the fluorescence of PCN-224(Zn)-Bpy(Ru)was almost completely quenched,and a longer average photoluminescence lifetime compared to PCN-224(Zn)-Bpy and PCN-224-Bpy(Ru)was observed.These suggest a low recombination rate of photogenerated carriers in PCN-224(Zn)-Bpy(Ru),which also supported by the higher photocurrent observed in PCN-224(Zn)-Bpy(Ru)compared to PCN-224(Zn)-Bpy and PCN-224-Bpy(Ru).In summary,the integrated Zn(II)-porphyrin and Ru(II)-bipyridyl moieties in PCN-224(Zn)-Bpy(Ru)play important roles of a photosensitizer and CO_(2)reduction as well as H_(2)O oxidation sites,and their efficient cooperation optimizes the band structure,thereby facilitating the coupling of CO_(2)reduction with H_(2)O oxidation and resulting in highperformance artificial photocatalytic CO_(2)reduction.展开更多
Organic matrices play an important role in biomineralization process. In order to explore the effect of both meso-tetrakis (4-hydroxylphenyl) porphyrin (THPP) and hydrogels on calcium carbonate mineralization,and cons...Organic matrices play an important role in biomineralization process. In order to explore the effect of both meso-tetrakis (4-hydroxylphenyl) porphyrin (THPP) and hydrogels on calcium carbonate mineralization,and consequently synthesize functional materials based on porphyrin and calcium carbonate with tunable shapes and optical properties,a new kind of biomimetic mineralization system which combined THPP with three biopolymer hydrogels (gelatin,agarose and calcium alginate gels) was designed and investigated. A carbonate diffusion method based on the generation of CO2 by slow decomposition of ammonium hydrogen carbonate was adopted for calcium carbonate crystallization. The results show that both gelatin and alginate hydrogels exhibit the ability of stabilizing vaterite,while agarose only induces the formation of calcite. With participation of THPP in the mineralization environments,calcite is favored in all these hydrogels,while the crystal morphologies are greatly different from each other. These results indicate the perspective of THPP in regulating calcium carbonate crystallization and also provide a new strategy for fabricating advanced functional materials with controlled morphology and tunable optical properties based on calcium carbonate and THPP.展开更多
文摘The metal contents of Nigerian coal minerals were analyzed using an atomic absorption spectrophotometer. Calcium, Na, and Fe occurred as the major elements with concentrations ranging from 9 782 μg/g for Ca to 432 μg/g for Na whereas K, Mg, Mn, Ni, Cr, Zn, Pb, and Cu, which occurred at trace levels ranged from 673.73 μg/g for Mg to 2.97 μg/g for Mn. The results of the quantitative analysis of porphyrins extracted from the coal minerals showed that Onyeama coal has the highest amount of porphyrins (ca～0.96 μg/g) while Okpara has the lowest (ca～0.30 μg/g). The porphyrins were qualitatively characterized by a combination of thin layer chromatography (TLC), infrared, and ultraviolet-visible spectrophotometers. The results of the mid infrared analysis (MIR) showed the presence of absorption bands at 3 440 cm～1～3 450 cm-1 and 1 640 cm-1～1 680 cm-1 , which are owing to the stretching vibrations of N ─ H and C─ C of aromatics, with C─ H out of plane (oop) bending vibrations at wavenumbers less than 900 cm-1, all of which are characteristic absorptions of porphyrin free base. The ultraviolet-visible data showed prominent peaks at ～400 nm(Soret band) and at wavelength ranges of 535 nm～550 nm(β-band) and 565 nm～ 600 nm (α-band) for the coal porphyrins analyzed. The geochemical significance of the metals and porphyrins in coal minerals are discussed.
文摘Efficiently converting CO_(2)and H_(2)O into value-added chemicals using solar energy is a viable approach to address global warming and the energy crisis.However,achieving artificial photocatalytic CO_(2)reduction using H_(2)O as the reductant poses challenges is due to the difficulty in efficient cooperation among multiple functional moieties.Metal-organic frameworks(MOFs)are promising candidates for overall CO_(2)photoreduction due to their large surface area,diverse active sites,and excellent tailorability.In this study,we designed a metal-organic framework photocatalyst,named PCN-224(Zn)-Bpy(Ru),by integrating photoactive Zn(Ⅱ)-porphyrin and Ru(Ⅱ)-bipyridyl moieties.In comparison,two isostructural MOFs just with either Zn(Ⅱ)-porphyrin or Ru(Ⅱ)-bipyridyl moiety,namely PCN-224-Bpy(Ru)and PCN-224(Zn)-Bpy were also synthesized.As a result,PCN-224(Zn)-Bpy(Ru)exhibited the highest photocatalytic conversion rate of CO_(2)to CO,with a production rate of 7.6μmol·g^(-1)·h^(-1)in a mixed solvent of CH_(3)CN and H_(2)O,without the need for co-catalysts,photosensitizers,or sacrificial agents.Mass spectrometer analysis detected the signals of^(13)CO(m/z=29),^(13)C^(18)O(m/z=31),^(16)O^(18)O(m/z=34),and^(18)O_(2)(m/z=36),confirming that CO_(2)and H_(2)O acted as the carbon and oxygen sources for CO and O_(2),respectively,thereby confirming the coupling of photocatalytic CO_(2)reduction with H_(2)O oxidation.In contrast,using PCN-224-Bpy(Ru)or PCN-224(Zn)-Bpy as catalysts under the same conditions resulted in significantly lower CO production rates of only 1.5 and 0μmol·g^(-1)·h^(-1),respectively.Mechanistic studies revealed that the lowest unoccupied molecular orbital(LUMO)potential of PCN-224(Zn)-Bpy(Ru)is more negative than the redox potentials of CO_(2)/CO,and the highest occupied molecular orbital(HOMO)potential is more positive than that of H_(2)O/O_(2),satisfying the thermodynamic requirements for overall photocatalytic CO_(2)reduction.In comparison,the HOMO potential of PCN-224(Zn)-Bpy without Ru(II)-bipyridyl moieties is less positive than that of H_(2)O/O_(2),indicating that the Ru(II)-bipyridyl moiety is thermodynamically necessary for CO_(2)reduction coupled with H_(2)O oxidation.Additionally,photoluminescence spectroscopy revealed that the fluorescence of PCN-224(Zn)-Bpy(Ru)was almost completely quenched,and a longer average photoluminescence lifetime compared to PCN-224(Zn)-Bpy and PCN-224-Bpy(Ru)was observed.These suggest a low recombination rate of photogenerated carriers in PCN-224(Zn)-Bpy(Ru),which also supported by the higher photocurrent observed in PCN-224(Zn)-Bpy(Ru)compared to PCN-224(Zn)-Bpy and PCN-224-Bpy(Ru).In summary,the integrated Zn(II)-porphyrin and Ru(II)-bipyridyl moieties in PCN-224(Zn)-Bpy(Ru)play important roles of a photosensitizer and CO_(2)reduction as well as H_(2)O oxidation sites,and their efficient cooperation optimizes the band structure,thereby facilitating the coupling of CO_(2)reduction with H_(2)O oxidation and resulting in highperformance artificial photocatalytic CO_(2)reduction.
基金Project supported by the Fundamental Research Funds for the Central Universities of ChinaProject (50573019) supported by the National Natural Science Foundation of ChinaProject (SKL2009-5) supported by Open Research Program of State Key Lab of Silicon Material,Zhejiang University,China
文摘Organic matrices play an important role in biomineralization process. In order to explore the effect of both meso-tetrakis (4-hydroxylphenyl) porphyrin (THPP) and hydrogels on calcium carbonate mineralization,and consequently synthesize functional materials based on porphyrin and calcium carbonate with tunable shapes and optical properties,a new kind of biomimetic mineralization system which combined THPP with three biopolymer hydrogels (gelatin,agarose and calcium alginate gels) was designed and investigated. A carbonate diffusion method based on the generation of CO2 by slow decomposition of ammonium hydrogen carbonate was adopted for calcium carbonate crystallization. The results show that both gelatin and alginate hydrogels exhibit the ability of stabilizing vaterite,while agarose only induces the formation of calcite. With participation of THPP in the mineralization environments,calcite is favored in all these hydrogels,while the crystal morphologies are greatly different from each other. These results indicate the perspective of THPP in regulating calcium carbonate crystallization and also provide a new strategy for fabricating advanced functional materials with controlled morphology and tunable optical properties based on calcium carbonate and THPP.
