The transformation of CO_(2)into cyclic carbonates via atom-economical cycloadditions with epoxides has recently attracted tremendous attention.On one hand,though many heterogeneous catalysts have been developed for t...The transformation of CO_(2)into cyclic carbonates via atom-economical cycloadditions with epoxides has recently attracted tremendous attention.On one hand,though many heterogeneous catalysts have been developed for this reaction,they typically suffer from disadvantages such as the need for severe reaction conditions,catalyst loss,and large amounts of soluble co-catalysts.On the other hand,the development of heterogeneous catalysts featuring multiple and cooperative active sites,remains challenging and desirable.In this study,we prepared a series of porous organic catalysts(POP-PBnCl-TPPMg-x)via the copolymerization metal-porphyrin compounds and phosphonium salt monomers in various ratios.The resulting materials contain both Lewis-acidic and Lewis-basic active sites.The molecular-level combination of these sites in the same polymer allows these active sites to work synergistically,giving rise to excellent performance in the cycloaddition reaction of CO_(2)with epoxides,under mild conditions(40℃ and 1 atm CO_(2))in the absence of soluble co-catalysts.POP-PBnCl-TPPMg-12 can also efficiently fixate CO_(2)under low-CO_(2)-concentration(15%v/v N2)conditions representative of typical CO_(2)compositions in industrial exhaust gases.More importantly,this catalyst shows excellent recyclability and can easily be separated and reused at least five times while maintaining its activity.In view of their heterogeneous nature and excellent catalytic performance,the obtained catalysts are promising candidates for the transformation of industrially generated CO_(2)into high value-added chemicals.展开更多
Global changes such as atmospheric CO_(2)enrichment often facilitate exotic plant invasions and alter soil arbuscular mycorrhizal fungi(AMF)community.However,it is still unclear whether the effects of CO_(2)enrichment...Global changes such as atmospheric CO_(2)enrichment often facilitate exotic plant invasions and alter soil arbuscular mycorrhizal fungi(AMF)community.However,it is still unclear whether the effects of CO_(2)enrichment on exotic plant invasions are associated with its effects on root-AMF symbiosis of invasive and native plants.To address this issue,the annual invasive plant Xanthium strumarium and two phylogenetically related annual natives were compared under ambient and elevated CO_(2)concentrations for three consecutive years.Atmospheric CO_(2)enrichment increased AMF colonization rates for the species only in few cases,and the invader did not benefit more from CO_(2)enrichment in terms of AMF colonization.Under ambient CO_(2)concentration,however,the invader had a higher AMF colonization rate than the natives in the first year of the study,which disappeared in the second and third year of the study due to the increase of AMF colonization rates in the natives but not in the invader.The influences of species,CO_(2)concentrations and planting year on AMF colonization were associated with their effects on both soil nutrient and AMF community,and the former may be more important as it also influenced the latter.Our results indicate that the invader could more quickly form symbiosis with soil AMF,contributing to adaptation and occupation of new habitats,and that it is necessary to consider the roles of AMF and the effects of time when determining the effects of global changes such as atmospheric CO_(2)enrichment on exotic plant invasions.展开更多
文摘The transformation of CO_(2)into cyclic carbonates via atom-economical cycloadditions with epoxides has recently attracted tremendous attention.On one hand,though many heterogeneous catalysts have been developed for this reaction,they typically suffer from disadvantages such as the need for severe reaction conditions,catalyst loss,and large amounts of soluble co-catalysts.On the other hand,the development of heterogeneous catalysts featuring multiple and cooperative active sites,remains challenging and desirable.In this study,we prepared a series of porous organic catalysts(POP-PBnCl-TPPMg-x)via the copolymerization metal-porphyrin compounds and phosphonium salt monomers in various ratios.The resulting materials contain both Lewis-acidic and Lewis-basic active sites.The molecular-level combination of these sites in the same polymer allows these active sites to work synergistically,giving rise to excellent performance in the cycloaddition reaction of CO_(2)with epoxides,under mild conditions(40℃ and 1 atm CO_(2))in the absence of soluble co-catalysts.POP-PBnCl-TPPMg-12 can also efficiently fixate CO_(2)under low-CO_(2)-concentration(15%v/v N2)conditions representative of typical CO_(2)compositions in industrial exhaust gases.More importantly,this catalyst shows excellent recyclability and can easily be separated and reused at least five times while maintaining its activity.In view of their heterogeneous nature and excellent catalytic performance,the obtained catalysts are promising candidates for the transformation of industrially generated CO_(2)into high value-added chemicals.
基金supported by the National Natural Science Foundation of China(31971557,31670545 and 31470575)the National Key R&D Program of China(2017YFC1200101).
文摘Global changes such as atmospheric CO_(2)enrichment often facilitate exotic plant invasions and alter soil arbuscular mycorrhizal fungi(AMF)community.However,it is still unclear whether the effects of CO_(2)enrichment on exotic plant invasions are associated with its effects on root-AMF symbiosis of invasive and native plants.To address this issue,the annual invasive plant Xanthium strumarium and two phylogenetically related annual natives were compared under ambient and elevated CO_(2)concentrations for three consecutive years.Atmospheric CO_(2)enrichment increased AMF colonization rates for the species only in few cases,and the invader did not benefit more from CO_(2)enrichment in terms of AMF colonization.Under ambient CO_(2)concentration,however,the invader had a higher AMF colonization rate than the natives in the first year of the study,which disappeared in the second and third year of the study due to the increase of AMF colonization rates in the natives but not in the invader.The influences of species,CO_(2)concentrations and planting year on AMF colonization were associated with their effects on both soil nutrient and AMF community,and the former may be more important as it also influenced the latter.Our results indicate that the invader could more quickly form symbiosis with soil AMF,contributing to adaptation and occupation of new habitats,and that it is necessary to consider the roles of AMF and the effects of time when determining the effects of global changes such as atmospheric CO_(2)enrichment on exotic plant invasions.
