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Covalently tethering disulfonic acid moieties onto polyoxometalate boosts acid strength and catalytic performance for hydroxyalkylation/alkylation reaction

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Science China Chemistry 2022年第4期65卷 699-709页

作者： Lifei Lian Yubing Liu Xianfeng Yi Hanbin Hu Xiang Chen Hongqiang Li Wei Chen Anming Zheng Yu-Fei Song state key laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBeijing 100029China Wuhan Center for magnetic resonance Key Laboratory of Magnetic Resonance in Biological SystemsState Key Laboratory of Magnetic Resonance and Atomic and Molecular PhysicsWuhan Institute of Physics and MathematicsChinese Academy of SciencesWuhan 430071China

Solid acid catalysts are widely used in the production of various high-value added and industrially important chemicals.Although the use of organosilicon compounds to modify the vacancy site has been extensively studied,the covalent tethering-SO_(3)H functionalized organosilicon modified polyoxometalates(POMs)has been rarely reported.In this work,two catalysts(TBA_(4)[SiW_(11)O_(39)(O(SiC_(3)H_(6)SO_(3)H)_(2))](compound 2)and TBA_(4)[SiW_(11)O_(39)(O(SiC_(8)H_(8)SO_(3)H)_(2))](compound 3))were synthesized successfully through covalently grafting different sulfonic acid(-SO_(3)H)groups onto[SiW_(11)O_(39)]^(8−)cluster,respectively.Compound 2 was achieved by surface grafting and in situ oxidation(3-mercaptopropyl)-trimethoxysilane,while compound 3 was achieved by surface grafting of 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane.Strong Brønsted acid strength of compounds 2 and 3 can be demonstrated by different methods including potentiometric titration,pyridine adsorption studies,and the ^(31)P trimethylphosphine oxides(TMPO)nuclear magnetic resonance(NMR).The systematic investigation of the relationship among POM structures,acid strength,and electron density was carried out based on density functional theory(DFT)calculation and experimental results,which revealed that covalent modification of compounds 2 and 3 decreased the electron density of the O-H bond,and promoted the release of H^(+).When applied in hydroxyalkylation/alkylation(HAA)reaction of 2-methylfuran(2-MF)with cyclohexanone,compound 2 exhibited better catalytic performance with conversion of ~93%,monocyclic fuel precursors(1a)yield of 79.9% and selectivity of 85.7% than compound 3,which can be attributed to strong Brønsted acid and the intramolecular hydrogen-bonding interactions between the neighboring -SO_(3)H moieties in compound 2.Finally,compound 2 also showed excellent catalytic activity in the HAA reaction of 2-MF with several different aldehydes and ketones(e.g.,furfuraldehyde,5-methylfurfuraldehyde,acetone,butyraldehyde and 4-methoxybenzald

关键词： polyoxometalates sulfonic acid covalent modifications acid catalysis alkylation reaction

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Recent advances in solid-state NMR of zeolite catalysts

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National Science Review 2022年第9期9卷 79-101页

作者： Weiyu Wang Jun Xu Feng Deng National Center for magnetic resonance in Wuhan State Key Laboratory of Magnetic Resonance and Atomic and Molecular PhysicsWuhan Institute of Physics and MathematicsInnovation Academy for Precision Measurement Science and TechnologyChinese Academy of Sciences University of Chinese Academy of Sciences

Zeolites are important inorganic crystalline microporous materials with a broad range of applications in the areas of catalysis, ion exchange, and adsorption/separations. Solid-state nuclear magnetic resonance(NMR) spectroscopy has proven to be a powerful tool in the study of zeolites and relevant catalytic reactions because of its advantage in providing atomic-level insights into molecular structure and dynamic behavior. In this review, we provide a brief discussion on the recent progress in exploring framework structures, catalytically active sites and intermolecular interactions in zeolites and metal-containing ones by using various solid-state NMR methods. Advances in the mechanistic understanding of zeolite-catalysed reactions including methanol and ethanol conversions are presented as selected examples. Finally, we discuss the prospect of the solid-state NMR technique for its application in zeolites.

关键词： solid-state NMR zeolites characterization active sites reaction mechanism

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Detection of a temporal salient object benefits from visual stimulus-specific adaptation in avian midbrain inhibitory nucleus

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Integrative Zoology 2024年第2期19卷 288-306页

作者： Jiangtao WANG Xiaoping RAO Shuman HUANG Zhizhong WANG Xiaoke NIU Minjie ZHU Songwei WANG Li SHI Department of Automation Zhengzhou University School of Electrical EngineeringZhengzhouChina State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics National Center for Magnetic Resonance in WuhanKey Laboratory of Magnetic Resonance in Biological SystemsInnovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhanChina Department of Automation Tsinghua UniversityBeijingChina

Food and predators are the most noteworthy objects for the basic survival of wild animals,and both are often deviant in both spatial and temporal domains and quickly attract an animal’s attention.Although stimulus-specific adaptation(SSA)is considered a potential neural basis of salient sound detection in the temporal domain,related research on visual SSA is limited and its relationship with temporal saliency is uncertain.The avian nucleus isthmi pars magnocellularis(Imc),which is central to midbrain selective attention network,is an ideal site to investigate the neural correlate of visual SSA and detection of a salient object in the time domain.Here,the constant order paradigm was applied to explore the visual SSA in the Imc of pigeons.The results showed that the firing rates of Imc neurons gradually decrease with repetitions of motion in the same direction,but recover when a motion in a deviant direction is presented,implying visual SSA to the direction of a moving object.Furthermore,enhanced response for an object moving in other directions that were not presented ever in the paradigm is also observed.To verify the neural mechanism underlying these phenomena,we introduced a neural computation model involving a recoverable synaptic change with a“center-surround”pattern to reproduce the visual SSA and temporal saliency for the moving object.These results suggest that the Imc produces visual SSA to motion direction,allowing temporal salient object detection,which may facilitate the detection of the sudden appearance of a predator.

关键词： adaptation attention model pigeon saliency

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Protein dynamics elucidated by NMR technique

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Protein & Cell 2013年第10期4卷 726-730页

作者： Conggang Li Chun Tang Maili Liu key laboratory of magnetic resonance in Biological Systems Wuhan Center for Magnetic ResonanceState Key Laboratory of Magnetic Resonance and Atomic and Molecular PhysicsWuhan Institute of Physics and MathematicsChinese Academy of SciencesWuhan 430071China

In 1957,Christian Anfinsen postulated his famous dogma based on the study of ribonuclease(Sela et al.,1957),stating that the amino acid sequence of a protein determines its tertiary structure,a unique and kinetically accessible energy minimum,in a given environment.As a result,determination of a global energy minimum,or the most populated structure,has been the main focus of structural biology in the ensuing half a century.With more and more structures have been determined,people have gain some insights of why protein functions,but the detailed mechanisms and the function process,or how protein functions,remains elusive.

关键词： elucidated structure dynamics

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Two-Photon Excited state Dynamics of Dark Rydberg and Bright Valence states in Furan

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Chinese physics Letters 2017年第4期34卷 26-29页

作者：龙金友胡春龙张冰 State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Chinese Academy of Sciences Wuhan 430071

Two-photon absorption in systems with parity permits access to states that cannot be directly prepared by one-photon absorption. Here we investigate ultrafast internal conversion （IC） dynamics of furan by using this strategy in combination with femtosecond time-resolved photoelectron imaging. The dark Rydberg S1 and bright valence S2 states are simultaneously excited by two photons of 405 nm, and then ionized by two photons of 800nm. The IC from S2 to S1 is clearly observed and extracted from the time dependence of the higher photoelectron kinetic energy （PKE） component. More importantly, the internal conversions to hot So from directly-prepared S1 and secondarily-populated S1 are unambiguously identified by the time-dependence of the lower PKE component. The average lifetime of the S2 and S1 states is measured to be 29 fs. The internal conversions of S2 to S1, S1 to hot So occur on estimated timescales of 15.4 fs and 38 fs, respectively.

关键词： Si Two-Photon Excited state Dynamics of Dark Rydberg and Bright Valence states in Furan

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Targeted Catalytic Cracking to Olefins(TCO):Reaction Mechanism,Production Scheme,and Process Perspectives

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Engineering 2023年第11期30卷 100-109页

作者： Youhao Xu Yanfen Zuo Wenjie Yang Xingtian Shu Wei Chen Anmin Zheng Research Institute of Petroleum Processing SinopecBeijing 100083China Economics and Development Research Institute SinopecBeijing 100029China State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics National Center for Magnetic Resonance in WuhanKey Laboratory of Magnetic Resonance in Biological SystemsWuhan Institute of Physics and MathematicsInnovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430071China

Light olefins are important organic building blocks in the chemicals industry.The main low-carbon olefin production methods,such as catalytic cracking and steam cracking,have considerable room for improvement in their utilization of hydrocarbons.This review provides a thorough overview of recent studies on catalytic cracking,steam cracking,and the conversion of crude oil processes.To maximize the production of light olefins and reduce carbon emissions,the perceived benefits of various technologies are examined.Taking olefin generation and conversion as a link to expand upstream and downstream processes,a targeted catalytic cracking to olefins(TCO)process is proposed to meet current demands for the transformation of oil refining into chemical production.The main innovations of this process include a multiple feedstock supply,the development of medium-sized catalysts,and a diameter-transformed fluidizedbed reactor with different feeding schemes.In combination with other chemical processes,TCO is expected to play a critical role in enabling petroleum refining and chemical processes to achieve low carbon dioxide emissions.

关键词： Light olefins Steam cracking Catalytic cracking TCO process Oil processing revolution

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Unraveling templated-regulated distribution of isolated SiO4 tetrahedra in silicoaluminophosphate zeolites with high-throughput computations

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National Science Review 2022年第9期9卷 19-27页

作者： Yan Li Chao Shi Lin Li Guoju Yang Junyan Li Jun Xu Qinfen Gu Xingxing Wang Ji Han Tianjun Zhang Yi Li Jihong Yu state key laboratory of Inorganic Synthesis and Preparative Chemistry Jilin University School of Textile and Clothing Yancheng Institute of Technology State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics National Center for Magnetic Resonance in Wuhan Wuhan Institute of Physics and MathematicsInnovation Academy for Precision Measurement Science and TechnologyChinese Academy of Sciences Australian Synchrotron International Center of Future Science Jilin University

Silicoaluminophosphate(SAPO) zeolites are well-known catalytic materials because of the mild acidity originating from the isolated SiO4tetrahedra in their frameworks. Regulating the distribution of isolated SiO4tetrahedra in SAPO zeolites is formidably challenging because SiO4tetrahedra tend to agglomerate to form Si islands and the isolated SiO4tetrahedra are difficult to determine using conventional characterization techniques. Here we synthesized Si-island-free SAPO-35 zeolites by using N-methylpiperidine as a new template, which exhibited excellent thermal stability compared to conventional SAPO-35 zeolites and a substantially improved methanol-to-olefins catalytic lifetime even comparable to that of commercial SAPO-34 zeolites. More strikingly, with the aid of high-throughput computations on 44 697 structure models combined with various state-of-the-art characterization techniques, for the first time, we reveal that the host–guest interactions between template molecules and SAPO frameworks determine the specific distributions of isolated SiO4tetrahedra, which are responsible for the improvement in the chemical properties of zeolites. Our work provides an insight into the template-based regulation of isolated SiO4tetrahedra in SAPO zeolites, which opens a new avenue in the discovery of promising zeolite catalysts with optimal Si O4distribution.

关键词： acidity computational chemistry heterogeneous catalysis structure–activity relationships zeolites

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Quench dynamics of ultracold atoms in one-dimensional optical lattices with artificial gauge fields

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Chinese physics B 2017年第8期26卷 353-360页

作者：蔡小明 State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and MathematicsChinese Academy of SciencesWuhan 430071China

We study the quench dynamics of noninteracting ultracold atoms loaded in one-dimensional （1D） optical lattices with artificial gauge fields, which are modeled by lattices with complex hopping coefficients. After suddenly changing the hopping coefficient, time evolutions of the density distribution, momentum distribution, and mass current at the center are studied for both finite uniform systems and trapped systems. Effects of filling factor, system size, statistics, harmonic trap, and phase difference in hopping are identified, and some interesting phenomena show up. For example, for a finite uniform fermionic system shock and rarefaction wave plateaus are formed at two ends, whose wave fronts move linearly with speed equaling to the maximal absolute group velocity. While for a finite uniform bosonic system the whole density distribution moves linearly at the group velocity. Only in a finite uniform fermionic system there can be a constant quasi- steady-state current, whose amplitude is decided by the phase difference and filling factor. The quench dynamics can be tested in ultracold atoms with minimal modifications of available experimental techniques, and it is a very interesting and fundamental example of the transport phenomena and the nonequilibrium dynamics.

关键词： nonequilibrium dynamics 1D optical Lattice artificial gauge field quasi-steady-state current

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Controllable growth of low-dimensional nanostructures on well-defined surfaces

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Chinese physics B 2013年第9期22卷 120-134页

作者：秦志辉 State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and MathematicsChinese Academy of Sciences

The controllable growth of nanostructures with desired geometric order and well-defined shapes has stimulated great interest due to its applicability in the development of microelectronic devices. Self-assembly is an efficient and versatile way to guide the atoms or molecules into low-dimensional nanostructures as a consequence of balancing complex interplay between adsorbate-adsorbate and adsorbate-substrate interfacial interactions. The tailoring of low-dimensional nanostruc- tures by control of inter-adsorbate and adsorbate-substrate interfacial interactions is reviewed. Such inherent interactions greatly influence not only the size and shape of the growing nanostructures, but also their chemical identity. The degree of interaction between adsorbates can be controlled via preparation procedures, opening up the study of the influence of this phenomenon with respect to reactivity and catalytic behavior. The formation of well-defined molecular layers can be controlled not only by repulsive molecule-molecule interaction but also by symmetry matching or charge transfer be- tween adsorbed molecules and the substrate. It has become obvious that inter-adsorbate and adsorbate-substrate interfacial interactions can be tuned to fabricate diverse surface nanostructures from semiconductor, metallic, and molecular materials.

关键词： nanostructures self-assembly intermolecular interactions scanning tunneling microscopy

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Stark spectrum of barium in highly excited Rydberg states

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Chinese physics B 2013年第1期22卷 179-182页

作者：杨海峰高伟成红柳晓军刘红平 State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Chinese Academy of Sciences

We present observations of Stark spectra of barium in highly excited Rydberg states in the energy region around n = 35. The one-photon excitation concerns the π transition. The observed Stark spectra at electric fields ranging from 0 to 60 V.cm-1 are well explained by the diagonalization of the Hamiltonian incorporating the core effects. From the Stark maps, the anti-crossings between energy levels are identified experimentally and theoretically. The time of flight spectra at the specified Stark states are recorded, where the deceleration and acceleration of barium atoms are observed. This is very consistent with the prediction derived from the Stark maps from the point of view of energy conservation.

关键词： Stark effect barium time of flight

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