Solid-aqueous interfaces and phenomena occurring at those interfaces are ubiquitously found in a plethora of chemical systems.When it comes to heterogeneous catalysis,however,our understanding of chemical transformati...Solid-aqueous interfaces and phenomena occurring at those interfaces are ubiquitously found in a plethora of chemical systems.When it comes to heterogeneous catalysis,however,our understanding of chemical transformations at solid-aqueous interfaces is relatively limited and primitive.This review phenomenologically describes a selection of water-engendered effects on the catalytic behavior for several prototypical acid-base-catalyzed reactions over solid catalysts,and critically assesses the general and special roles of water molecules,structural moieties derived from water,and ionic species that are dissolved in it,with an aim to extract novel concepts and principles that underpin heterogeneous acid-base catalysis in the aqueous phase.For alcohol dehydration catalyzed by solid Bronsted acids,rate inhibition by water is most typically related to the decrease in the acid strength and/or the preferential solvation of adsorbed species over the transition state as water molecules progressively solvate the acid site and form extended networks wherein protons are mobilized.Water also inhibits dehydration kinetics over most Lewis acid-base catalysts by competitive adsorption,but a few scattered reports reveal substantial rate enhancements due to the conversion of Lewis acid sites to Brønsted acid sites with higher catalytic activities upon the introduction of water.For aldol condensation on catalysts exposing Lewis acid-base pairs,the addition of water is generally observed to enhance the rate when C–C coupling is rate-limiting,but may result in rate inhibition by site-blocking when the initial unimolecular deprotonation is rate-limiting.Water can also promote aldol condensation on Brønsted acidic catalysts by facilitating inter-site communication between acid sites through hydrogen-bonding interactions.For metallozeolite-catalyzed sugar isomerization in aqueous media,the nucleation and networking of intrapore waters regulated by hydrophilic entities causes characteristic enthalpy-entropy tradeoffs as these water moieties interact with kinetically relevant hydride transfer transition states.The discussed examples collectively highlight the utmost importance of hydrogen-bonding interactions and ionization of covalently bonded surface moieties as the main factors underlying the uniqueness of water-mediated interfacial acid-base chemistries and the associated solvation effects in the aqueous phase or in the presence of water.A perspective is also provided for future research in this vibrant field.展开更多
The state equation for strangeon matter is very stiff due to the non-relativistic nature of its particles and their repulsive interaction, such that pulsar masses as high as ～ 3M would be expected. However, an adiaba...The state equation for strangeon matter is very stiff due to the non-relativistic nature of its particles and their repulsive interaction, such that pulsar masses as high as ～ 3M would be expected. However, an adiabatic sound speed, cs = √P/ρ, is usually superluminal in strangeon matter, and the dynamic response of a strangeon star （e.g., binary merger） is not tractable in numerical simulations. In this study, we examined signal propagation in strangeon matter and calculate the actual propagation speed, Csignal. We found that the causality condition, Csignal 〈 c, is satisfied and the signal speed is presented as a function of stellar radius.展开更多
文摘Solid-aqueous interfaces and phenomena occurring at those interfaces are ubiquitously found in a plethora of chemical systems.When it comes to heterogeneous catalysis,however,our understanding of chemical transformations at solid-aqueous interfaces is relatively limited and primitive.This review phenomenologically describes a selection of water-engendered effects on the catalytic behavior for several prototypical acid-base-catalyzed reactions over solid catalysts,and critically assesses the general and special roles of water molecules,structural moieties derived from water,and ionic species that are dissolved in it,with an aim to extract novel concepts and principles that underpin heterogeneous acid-base catalysis in the aqueous phase.For alcohol dehydration catalyzed by solid Bronsted acids,rate inhibition by water is most typically related to the decrease in the acid strength and/or the preferential solvation of adsorbed species over the transition state as water molecules progressively solvate the acid site and form extended networks wherein protons are mobilized.Water also inhibits dehydration kinetics over most Lewis acid-base catalysts by competitive adsorption,but a few scattered reports reveal substantial rate enhancements due to the conversion of Lewis acid sites to Brønsted acid sites with higher catalytic activities upon the introduction of water.For aldol condensation on catalysts exposing Lewis acid-base pairs,the addition of water is generally observed to enhance the rate when C–C coupling is rate-limiting,but may result in rate inhibition by site-blocking when the initial unimolecular deprotonation is rate-limiting.Water can also promote aldol condensation on Brønsted acidic catalysts by facilitating inter-site communication between acid sites through hydrogen-bonding interactions.For metallozeolite-catalyzed sugar isomerization in aqueous media,the nucleation and networking of intrapore waters regulated by hydrophilic entities causes characteristic enthalpy-entropy tradeoffs as these water moieties interact with kinetically relevant hydride transfer transition states.The discussed examples collectively highlight the utmost importance of hydrogen-bonding interactions and ionization of covalently bonded surface moieties as the main factors underlying the uniqueness of water-mediated interfacial acid-base chemistries and the associated solvation effects in the aqueous phase or in the presence of water.A perspective is also provided for future research in this vibrant field.
基金supported by the National Key R&D Program of China(Grant No.2017YFA0402600)the National Natural Science Foundation of China(Grant No.11225314)+1 种基金the Open Project Program of the Key Laboratory of Radio Astronomy and the Open Project Program of the Key Laboratory of FAST,NAOC,Chinese Academy of SciencesThe FAST FELLOWSHIP is supported by Special Funding for Advanced Users,budgeted and administrated by Center for Astronomical Mega-Science,Chinese Academy of Sciences(CAMS)
文摘The state equation for strangeon matter is very stiff due to the non-relativistic nature of its particles and their repulsive interaction, such that pulsar masses as high as ～ 3M would be expected. However, an adiabatic sound speed, cs = √P/ρ, is usually superluminal in strangeon matter, and the dynamic response of a strangeon star （e.g., binary merger） is not tractable in numerical simulations. In this study, we examined signal propagation in strangeon matter and calculate the actual propagation speed, Csignal. We found that the causality condition, Csignal 〈 c, is satisfied and the signal speed is presented as a function of stellar radius.
