Supported metal oxide catalysts have garnered significantattention in oxidative dehydrogenation(ODH)due to their tunable metal-support interactions.The pentacoordinate Al^(3+)(Al_(V)^(3+))in γ-Al_(2)O_(3)supports pla...Supported metal oxide catalysts have garnered significantattention in oxidative dehydrogenation(ODH)due to their tunable metal-support interactions.The pentacoordinate Al^(3+)(Al_(V)^(3+))in γ-Al_(2)O_(3)supports plays a pivotal role in modulating metal-support interaction.This study investigates oxalic acid(OA)pretreatment as a defect engineering strategy to enhance the catalytic performance of CeO_(2)/γ-Al_(2)O_(3)in cyclohexane ODH.Through integrated characterization(XRD,27Al MAS NMR,H_(2)-TPR,TPRO,MS,XPS)and catalytic testing,we demonstrate that optimal OA treatment(1:10 ratio)eliminates 100%of surface Al_(V)^(3+)defects while enhancing CeO_(2)crystallinity and interfacial oxygen mobility.The removal of Al_(V)^(3+)species restructures metal-support interaction,accelerating interfacial oxygen mobility.In oxidation dehydrogenation of cyclohexane,the modified CeO_(2)/γ-Al_(2)O_(3)achieves 29%of cyclohexane conversion with stable selectivity of 49%cyclohexene.These findingsprovide an initial framework for designing redox-active catalysts via targeted support modificationin CeO_(2)/γ-Al_(2)O_(3)systems,emphasizing the relationship between metal-support interaction and oxygen mobility.展开更多
The reaction between D-glucose, D-ribose and 2, 2,2-trimethoxy-4, 5-diphenyl-2, 2-dihydro-1, 3, 2-dioxaphospholene were investigates by P-31 NMR and FAB-MS. The results showed that there were a lot of differences in t...The reaction between D-glucose, D-ribose and 2, 2,2-trimethoxy-4, 5-diphenyl-2, 2-dihydro-1, 3, 2-dioxaphospholene were investigates by P-31 NMR and FAB-MS. The results showed that there were a lot of differences in the reactions via pentacoordinate phosphorus compound, and it should give it significant clue to the metabolism of carbohydrate phosphate in nature.展开更多
The reactions of 2-chloro-1,3,2-dioxaphospholane with various sodium salts of amino acids to afford the pentacoordinated spirophosphoranes containing amino acid were studied by NMR spectra techniques. The results show...The reactions of 2-chloro-1,3,2-dioxaphospholane with various sodium salts of amino acids to afford the pentacoordinated spirophosphoranes containing amino acid were studied by NMR spectra techniques. The results showed that natural alpha-amino acids had greater ability than beta-amino acids to form the pentacoordinated species, which is important in the biosynthesis and prebiotic synthesis of of oligopeptides and proteins.展开更多
Oxyphosphorane reacted with glucose to give disaccharide which was confirmed by FAB-MS and C-13-NMR. The mechanism for formation of oligosaccharides through the participation of phosphorus was proposed.
Four pentacoordinate complexes,1–4,of the type[Co(L^(1))X_(2)]and[Co(L^(2))X_(2)](where L^(1)=2,6-bis(1-octyl-1H-benzimidazol-2-yl)pyridine for 1 and 2,L^(2)=2,6-bis(1-dodecyl-1H-benzimidazol-2-yl)pyridine for 3 and ...Four pentacoordinate complexes,1–4,of the type[Co(L^(1))X_(2)]and[Co(L^(2))X_(2)](where L^(1)=2,6-bis(1-octyl-1H-benzimidazol-2-yl)pyridine for 1 and 2,L^(2)=2,6-bis(1-dodecyl-1H-benzimidazol-2-yl)pyridine for 3 and 4;X=Cl^(-)for 1 and 3,X=Br^(-)for 2 and 4)have been synthesized,and their structures have been determined by X-ray analysis.The DC magnetic investigation confirmed the high-spin and anisotropic behavior of the metal centers of the reported compounds,and magnetic data were analyzed with respect to the spin Hamiltonian and the Griffith–Figgis Hamiltonian.CASSCF-NEVPT2 analysis enabled us to identify triaxial magnetic anisotropy for 1 and 2 and axial anisotropy for 3 and 4,and we discuss thoroughly the relationship between geometry and orbital ordering.The g-tensor components of the ground Kramers doublet extracted from EPR spectroscopy are compatible with this prediction of magnetic anisotropy.Simulated FIRMS experimental data of 2,3 and 4 show very good agreement with theoretical calculations and provide precise values of zero-field splitting.The AC susceptibility measurements confirmed that the reported complexes were field-induced single-ion magnets.The slow relaxation of magnetization in 1 and 2 is mediated through two relaxation channels that are unusually close to each other.On the other hand,complexes 3 and 4 show the single-channel relaxation of magnetization,and their isostructural characteristic allowed us to study the relaxation changes caused solely by the replacement of terminal halido ligands.Finally,a wet lithographic technique has been used to evaluate both the processability of the complexes in solution and the preparation of microstructured films.展开更多
A new modification of borosilicate datolite,CaBSiO_(4)(OH),has been discovered using synchrotron-based in situ high-pressure single-crystal X-ray diffraction.The phase transition from low(I)to high(II)pressure modific...A new modification of borosilicate datolite,CaBSiO_(4)(OH),has been discovered using synchrotron-based in situ high-pressure single-crystal X-ray diffraction.The phase transition from low(I)to high(II)pressure modification is isosymmetric and occurs between 27 and 33 GPa.展开更多
The smallest molecules up to date containing a D5h pentacoordinate planar carbon(PPC)atom,CBe5 and CBe54-,are presented by means of ab initio calculations.To gain a better understanding about which electronic factors ...The smallest molecules up to date containing a D5h pentacoordinate planar carbon(PPC)atom,CBe5 and CBe54-,are presented by means of ab initio calculations.To gain a better understanding about which electronic factors contribute to their stabilization,natural bond orbital(NBO)analysis and the nucleus independent chemical shifts(NICS)were calculated.The data reported here suggest that D5h CBe5 isσaromaticity in nature,while in D5h CBe54-πaromaticity is dominating.The classical octet rule is well satisfied in both molecules,and is one of the fundamental reasons to understand the stability of the pentagon structures.The Be5 ring serves asσdonor in D5h CBe5,andπ-acceptor in D5h CBe54-.The D5h CBe54-possessing 18 valence electrons with a closed-shell electron configuration is the most plau-sible candidate for experimental detection.展开更多
Pentacoordinated Al(Al~Ⅴ)species in silica-alumina are promising to promote the formation of acid sites or act as surface defects for tailoring single-atom catalysts.However,pentahedral coordination(Al~Ⅴ)is rarely o...Pentacoordinated Al(Al~Ⅴ)species in silica-alumina are promising to promote the formation of acid sites or act as surface defects for tailoring single-atom catalysts.However,pentahedral coordination(Al~Ⅴ)is rarely observed in conventionally prepared silica-alumina.Here,we show that high population and dispersion of Al~Ⅴ species on the surface of amorphous silica-alumina(ASA)can be achieved by means of flame spray pyrolysis.High resolution TEM/EDX,high magnetic-field NMR and DFT calculations are employed to characterize the structure of as-prepared ASAs.Solid-state ^(27)Al multi-quantum MAS NMR experiments show that most of the Al~Ⅴspecies are formed independently from the alumina phase and are accessible for vip molecules on the surface.Upon water adsorption,these Al~Ⅴ species are transformed to Al~Ⅵ species,structurally similar to surface Al~Ⅳ species,as confirmed by DFT calculations.The outstanding catalytic activity of as-synthesized ASA is demonstrated using the in situ H/D exchange reaction with deuterated benzene as an example.The Al~Ⅴ-rich ASA provides a much lower activation energy(～30 kJ/mol)than that reported for zeolite H-ZSM-5(～60 kJ/mol).The superior catalytic performance is attributed to the high Al~Ⅴcontent promoting the surface active sites in ASA.The knowledge gained on the synthesis of Al~Ⅴ-rich ASAs and the nature of aluminum coordination in these materials could pave the way to more efficient silica-alumina based catalysts.展开更多
Pentacoordinate Al^(3+)(Al^(3+)_(penta))sites on alumina(Al_(2)O_(3))could anchor and stabilize the active site over the cata-lyst surface.The paper describes the specific effect of Al^(3+)_(penta) sites on the struct...Pentacoordinate Al^(3+)(Al^(3+)_(penta))sites on alumina(Al_(2)O_(3))could anchor and stabilize the active site over the cata-lyst surface.The paper describes the specific effect of Al^(3+)_(penta) sites on the structure and the catalytic performance of Al_(2)O_(3)supported Pt catalysts by modulating the quantity of Al^(3+)_(penta) sites.The Al^(3+)_(penta) site content of Al_(2)O_(3)exhibits a volcano-type profile as a function of calcination temperature due to the structural rearrangement.The loading of Pt and subsequent calcination can consume a significant portion of Al^(3+)_(penta) sites over the Al_(2)O_(3)support.We further find that,when the calcination temperature of the impregnated Al_(2)O_(3)is higher than the cal-cination temperature of Al_(2)O_(3)precursor,the structural rearrangement of Al^(3+)_(penta) sites could make Pt partially buried in Al_(2)O_(3).Consequently,this partially buried structure leads to relatively low conversion but high stability for propane dehydrogenation.This work further elucidates the stabilization mechanism of the Al^(3+)_(penta) site over Al_(2)O_(3)support.展开更多
A general method for the synthesis of bench-stable bis(difluoromethyl)pentacoordinate phosphoranes has been developed.The reaction is rapid,operationally simple,and easily scalable.The pentacoordinate phosphoranes can...A general method for the synthesis of bench-stable bis(difluoromethyl)pentacoordinate phosphoranes has been developed.The reaction is rapid,operationally simple,and easily scalable.The pentacoordinate phosphoranes can generate both difluoromethyl radical(·CF_(2)H)and difluorocarbene(:CF_(2))intermediates.Thus,a variety of fluoroalkylation transformations havebeen achieved by·CF_(2)H,such asoxidativedifluoromethylation of electron-deficient heterocycles,nickel/photoredox dual-catalyzed difluoromethylation of aryl bromides,and photoredox difluoromethylation of alkenes,or by:CF_(2),such as gem-difluorocyclopropanation of alkenes,base-promoted difluoromethylation of heteroatom nucleophiles,Pd-catalyzed difluoromethylation of arylboronic acids,and Cu-mediated trifluoromethylation of aryl iodides(via:CF_(2) and recombined CF_(3)-).These fluoroalkylation methods have been successfully applied to late-stage fluoroalkylation of drugs and drug-like molecules.展开更多
Pursuing new two-dimensional(2D)materials has been a hot topic in materials science,driven by their potential for diverse applications.Recent research has unveiled stable planar hypercoordinate motifs with unconventio...Pursuing new two-dimensional(2D)materials has been a hot topic in materials science,driven by their potential for diverse applications.Recent research has unveiled stable planar hypercoordinate motifs with unconventional geometric arrangements and bonding patterns that facilitate the synthesis of new 2D materials with diverse applications.Among these,yet the design of 2D transition metal systems featuring planar pentacoordinate boron(ppB)is particularly intriguing.Here we address this gap by proposing a novel family of transition metal boride monolayers(MBenes)composed of ppB and heptacoordinate M motifs.The novelty of our MBenes stems from their distinct atomic arrangements and bonding configurations,setting them apart from traditional 2D materials.High-throughput calculations identified 10 stable MBenes(with the stoichiometry of MB,M=Cr,Fe,Co,Ni,Cu,Mo,Pd,Ag,Pt,Au)with exceptional thermodynamic,dynamic,thermal,and mechanical stabilities attributed to strong BB covalent bonds and MB ionic interactions.Notably,five of these MBenes(M=Ni,Pd,Pt,Ag,Au)hold high promise as topological superconducting materials with superconducting transition temperatures of 2.4-5.2 K.This discovery not only enriches the family of topological superconducting materials but also opens new avenues for quantum device development.Meanwhile,FeB monolayer exhibits robust ferromagnetic properties with a high Curie temperature of~750 K,which is particularly significant for spintronics applications.In addition,NiB and CuB MBenes demonstrate extremely low sodium diffusion barriers(about 30 and 90 meV)and high sodium storage capacities(788 and 734 mAh g1,respectively),making them promising anode materials for sodium-ion batteries(SIBs).This study expands the selection of electrode materials for SIBs and mitigates some existing limitations in battery technology.Overall,these findings underscore the multifunctional potential of MBenes,positioning them as transformative materials for quantum computing,spintronics,and energy storage applications.展开更多
Amino acid methyl ester phosphates were synthesized and determined by using positive-ion mode dectrospmy ionization mass spectrometry（ESIMS） in combination with multistage tandem mass spectrometry. The fragmentation...Amino acid methyl ester phosphates were synthesized and determined by using positive-ion mode dectrospmy ionization mass spectrometry（ESIMS） in combination with multistage tandem mass spectrometry. The fragmentation pathways were investigated, and it was observed that most fragment ions contained the phosphoryl group. It was interesting to observe that the fragmentation pathways of the protonated molecule show some differences when compared with those of the sodium ion adduct. The methoxy group of amino acid methyl ester can migrate from the carbonyl group to the phosphoryl group in the sodium ion adduct.展开更多
The syntheses of chiral pentacoordinated fluoridosilicates and their conversion into fluorine-doped silica and mesoporous carbon are reported.Starting from 4H,4’H-2,2’-spirobi[benzo[d][1,3,2]dioxasiline](1)and 8,8’...The syntheses of chiral pentacoordinated fluoridosilicates and their conversion into fluorine-doped silica and mesoporous carbon are reported.Starting from 4H,4’H-2,2’-spirobi[benzo[d][1,3,2]dioxasiline](1)and 8,8’-di-tert-butyl-4H,4’H-2,2’-spirobi[benzo[d][1,3,2]dioxasiline](2),the corresponding fluorido complexes 3 and 4 were obtained by the addition of potassium fluoride to the spirocyclic silicon salicylic alcoholates 1 and 2 in the presence of 18-crown-6.The pentacoordinated geometry around the silicon atom of the SiO_(4)F type in 3 and 4 was proved using single-crystal X-ray diffraction analysis.DSC measurements were used to study the thermal behavior of the compounds with regard to their usability in the twin polymerization process.Hence,polymerization of 3 and 4 and the simultaneous twin polymerization of the fluoridosilicate 3 with spirocyclic 1 gave fluorine-doped phenolic resin/silica composites as confirmed by solid state NMR spectroscopic studies(^(1)H,^(13)C{1H},^(19)F,and^(29)Si{1H}).Carbonization of the as-obtained hybrid materials and subsequent treatment with hydrofluoric acid resulted in microporous carbon with surface areas up to 1060 m^(2)g^(-1).Calcination of the hybrid materials produced fluorine-doped silica with BET surface areas up to 239 m^(2)g^(-1).Additionally,the synthesis of hybrid materials using the additive assisted twin polymerization of 1 with either tetra-n-butylammonium fluoride or KF gave either microporous carbon(1219 m^(2)g^(-1))or mesoporous silica(687 m^(2)g^(-1)).展开更多
The Pt Sn/Al_(2)O_(3)catalyst is commonly used in commercial propane dehydrogenation(PDH)processes,but it faces challenges in the deactivation and periodic regeneration due to metal aggregation and coke deposition at ...The Pt Sn/Al_(2)O_(3)catalyst is commonly used in commercial propane dehydrogenation(PDH)processes,but it faces challenges in the deactivation and periodic regeneration due to metal aggregation and coke deposition at high temperatures.Although Al_(penta)^(3+)has been proven to be beneficial for enhancing catalytic stability,bottom-up synthesis protocols usually restrict their applications.Here,a facile post-treatment approach using acetic acid was applied to create color centers(electrons trapped within oxygen vacancies)onγ-Al_(2)O_(3).Notably,the content of Al_(penta)^(3+)was enriched to 18.3%.Then,the pre-established Pt Sn clusters were loaded.The electrons facilitated the formation of ultrafine Pt Sn nanoparticles(~2 nm),and the Al_(penta)^(3+)sites prevented the sintering of Pt Sn by constructing the strong Al_(penta)^(3+)–O–Sn bonds.Furthermore,the catalytic durability of the catalyst prepared by conventional impregnation methods was remarkably extended from 186 h for the color center-free sample to 1,000 h using the HAc–Al_(2)O_(3)support.This facile post-modification was further successfully extended to commercial Al_(2)O_(3)pellets without altering their mechanical properties,highlighting its potential in industrial applications.展开更多
Metal porphyrins are star molecules that possess welldefined coordination metal centers for versatile catalytic reactions.However,most previous work has focused on the correlations between in-plane symmetric configura...Metal porphyrins are star molecules that possess welldefined coordination metal centers for versatile catalytic reactions.However,most previous work has focused on the correlations between in-plane symmetric configuration of metal-N_(4)sites and their catalytic performance.Addressing the catalytic contribution of additional axial coordination to such symmetric configuration remains a challenge.Theoretical calculations revealed that axially anchoring an extra pyridine on the tetra-coordinated cobalt porphyrin(Co-N4)to construct penta-coordinated cobalt porphyrin(Co-N_(5))renders cobalt a higher electron density,thereby favoring the rate-determining O_(2)adsorption/activation and reducing the oxygen electroreduction barrier.Therefore,a well-defined Co-N_(5)site is rationally introduced into the azo-linked polymer framework for a fundamental structure-catalytic performance correlation study.As-prepared Co-N_(5)catalyst exhibits a 26 mV positive shift in half-wave potential compared with the pyridine-free Co-N_(4)counterpart,discloses a markedly higher power density(141.4 mW cm^(−2)),and possesses better long-term durability(over 160 h cycles)in a Zn-air battery.Moreover,such a Co-N_(5)catalyst also showcases potential applications for CO_(2)reduction with high CO_(2)-to-CO conversion faradic efficiency and better selectivity than the Co-N_(4)counterpart because coordination of the fifth pyridine evokes electronic localization that suppresses a competitive side reaction.This work proves the positive electrocatalytic contribution of axial penta-coordination on well-defined metalporphyrin-based catalysts and offers atomic understanding of the structure-performance correlation on single atom catalysts for future catalyst design.展开更多
基金support from Zhejiang Provincial Natural Science Foundation of China(LZ23B060001).
文摘Supported metal oxide catalysts have garnered significantattention in oxidative dehydrogenation(ODH)due to their tunable metal-support interactions.The pentacoordinate Al^(3+)(Al_(V)^(3+))in γ-Al_(2)O_(3)supports plays a pivotal role in modulating metal-support interaction.This study investigates oxalic acid(OA)pretreatment as a defect engineering strategy to enhance the catalytic performance of CeO_(2)/γ-Al_(2)O_(3)in cyclohexane ODH.Through integrated characterization(XRD,27Al MAS NMR,H_(2)-TPR,TPRO,MS,XPS)and catalytic testing,we demonstrate that optimal OA treatment(1:10 ratio)eliminates 100%of surface Al_(V)^(3+)defects while enhancing CeO_(2)crystallinity and interfacial oxygen mobility.The removal of Al_(V)^(3+)species restructures metal-support interaction,accelerating interfacial oxygen mobility.In oxidation dehydrogenation of cyclohexane,the modified CeO_(2)/γ-Al_(2)O_(3)achieves 29%of cyclohexane conversion with stable selectivity of 49%cyclohexene.These findingsprovide an initial framework for designing redox-active catalysts via targeted support modificationin CeO_(2)/γ-Al_(2)O_(3)systems,emphasizing the relationship between metal-support interaction and oxygen mobility.
文摘The reaction between D-glucose, D-ribose and 2, 2,2-trimethoxy-4, 5-diphenyl-2, 2-dihydro-1, 3, 2-dioxaphospholene were investigates by P-31 NMR and FAB-MS. The results showed that there were a lot of differences in the reactions via pentacoordinate phosphorus compound, and it should give it significant clue to the metabolism of carbohydrate phosphate in nature.
文摘The reactions of 2-chloro-1,3,2-dioxaphospholane with various sodium salts of amino acids to afford the pentacoordinated spirophosphoranes containing amino acid were studied by NMR spectra techniques. The results showed that natural alpha-amino acids had greater ability than beta-amino acids to form the pentacoordinated species, which is important in the biosynthesis and prebiotic synthesis of of oligopeptides and proteins.
文摘Oxyphosphorane reacted with glucose to give disaccharide which was confirmed by FAB-MS and C-13-NMR. The mechanism for formation of oligosaccharides through the participation of phosphorus was proposed.
基金Slovak grant agencies(Slovakia:APVV-18-0197,APVV-18-0016,APVV-19-0087,VEGA 1/0029/22,KEGA 018-STU-4)are acknowledged for financial supportsupport from the Grant Agency of the Czech Republic(GAČR 22-23760S)+7 种基金This article was written thanks to generous support through the Operational Program Integrated Infrastructure for the project:“Strategic research in the field of SMART monitoring,treatment and preventive protection against coronavirus(SARS-CoV-2)”,Project no.313011ASS8,co-financed by the European Regional Development Fundsupport from the institutional sources of the Department of Inorganic Chemistry,PalackýUniversity Olomouc,Czech Republic and the Ministry of Education,Youth and Sports of the Czech Republic under the project CEITEC 2020(LTAUSA19060)support from the MŠVVaŠof the Slovak Republic within the Research and Development Operational Program for the project“University Science Park of STU Bratislava”(ITMS project no.26240220084)co-funded by the European Regional Development Fundthe HPC center at the Slovak University of Technology in Bratislava,which is a part of the Slovak Infrastructure of High Performance Computing(SIVVP project,ITMS code 26230120002,funded by European regional development funds,ERDF),for computational time and resources made availablesupport from an internal grant from Brno University of Technology CEITEC VUT-J-20-6512Furthermore,CzechNanoLab project LM2018110 funded by MEYS CR is gratefully acknowledged for financial support for measurements/sample preparation at the CEITEC Nano Research Infrastructuresupport from a Brno PhD Talent 2018 scholarshipfunding from the MŠMT LTAUSA19060 project through the INTER-EXCELLENCE program.
文摘Four pentacoordinate complexes,1–4,of the type[Co(L^(1))X_(2)]and[Co(L^(2))X_(2)](where L^(1)=2,6-bis(1-octyl-1H-benzimidazol-2-yl)pyridine for 1 and 2,L^(2)=2,6-bis(1-dodecyl-1H-benzimidazol-2-yl)pyridine for 3 and 4;X=Cl^(-)for 1 and 3,X=Br^(-)for 2 and 4)have been synthesized,and their structures have been determined by X-ray analysis.The DC magnetic investigation confirmed the high-spin and anisotropic behavior of the metal centers of the reported compounds,and magnetic data were analyzed with respect to the spin Hamiltonian and the Griffith–Figgis Hamiltonian.CASSCF-NEVPT2 analysis enabled us to identify triaxial magnetic anisotropy for 1 and 2 and axial anisotropy for 3 and 4,and we discuss thoroughly the relationship between geometry and orbital ordering.The g-tensor components of the ground Kramers doublet extracted from EPR spectroscopy are compatible with this prediction of magnetic anisotropy.Simulated FIRMS experimental data of 2,3 and 4 show very good agreement with theoretical calculations and provide precise values of zero-field splitting.The AC susceptibility measurements confirmed that the reported complexes were field-induced single-ion magnets.The slow relaxation of magnetization in 1 and 2 is mediated through two relaxation channels that are unusually close to each other.On the other hand,complexes 3 and 4 show the single-channel relaxation of magnetization,and their isostructural characteristic allowed us to study the relaxation changes caused solely by the replacement of terminal halido ligands.Finally,a wet lithographic technique has been used to evaluate both the processability of the complexes in solution and the preparation of microstructured films.
基金supported by the Russlian Foundation for Basic Research(grant 17-05-01027)(to SVK)by the People Programme(Marie Curie Actions)of the European Union's Seventh Framework Programme FP7/2007-2013/under the REA grant agreement PIRSES-GA-2013-610547-TAMER(for LAG and SVK).Wethank Professor I.V.Pekov(Moscow State)。
文摘A new modification of borosilicate datolite,CaBSiO_(4)(OH),has been discovered using synchrotron-based in situ high-pressure single-crystal X-ray diffraction.The phase transition from low(I)to high(II)pressure modification is isosymmetric and occurs between 27 and 33 GPa.
基金the Research Fund for the Doctoral Program of Higher Education(Grant No.20070533142)the China Postdoctoral Science Foundation(Grant No.20070410139)+1 种基金the 111 Project of China(Grant No.B07012)the National Natu-ral Science Foundation of China(Grant No.20802093)
文摘The smallest molecules up to date containing a D5h pentacoordinate planar carbon(PPC)atom,CBe5 and CBe54-,are presented by means of ab initio calculations.To gain a better understanding about which electronic factors contribute to their stabilization,natural bond orbital(NBO)analysis and the nucleus independent chemical shifts(NICS)were calculated.The data reported here suggest that D5h CBe5 isσaromaticity in nature,while in D5h CBe54-πaromaticity is dominating.The classical octet rule is well satisfied in both molecules,and is one of the fundamental reasons to understand the stability of the pentagon structures.The Be5 ring serves asσdonor in D5h CBe5,andπ-acceptor in D5h CBe54-.The D5h CBe54-possessing 18 valence electrons with a closed-shell electron configuration is the most plau-sible candidate for experimental detection.
基金the financial supports by Australian Research Council Discovery Projects (DP150103842)Discovery Earlier Career Research Project (DE190101618)+1 种基金the Faculty's MCR Scheme, Energy and Materials Clusters at the University of Sydneythe support by the National Natural Science Foundation of China (21522310, 21473244 and 21210005)
文摘Pentacoordinated Al(Al~Ⅴ)species in silica-alumina are promising to promote the formation of acid sites or act as surface defects for tailoring single-atom catalysts.However,pentahedral coordination(Al~Ⅴ)is rarely observed in conventionally prepared silica-alumina.Here,we show that high population and dispersion of Al~Ⅴ species on the surface of amorphous silica-alumina(ASA)can be achieved by means of flame spray pyrolysis.High resolution TEM/EDX,high magnetic-field NMR and DFT calculations are employed to characterize the structure of as-prepared ASAs.Solid-state ^(27)Al multi-quantum MAS NMR experiments show that most of the Al~Ⅴspecies are formed independently from the alumina phase and are accessible for vip molecules on the surface.Upon water adsorption,these Al~Ⅴ species are transformed to Al~Ⅵ species,structurally similar to surface Al~Ⅳ species,as confirmed by DFT calculations.The outstanding catalytic activity of as-synthesized ASA is demonstrated using the in situ H/D exchange reaction with deuterated benzene as an example.The Al~Ⅴ-rich ASA provides a much lower activation energy(～30 kJ/mol)than that reported for zeolite H-ZSM-5(～60 kJ/mol).The superior catalytic performance is attributed to the high Al~Ⅴcontent promoting the surface active sites in ASA.The knowledge gained on the synthesis of Al~Ⅴ-rich ASAs and the nature of aluminum coordination in these materials could pave the way to more efficient silica-alumina based catalysts.
基金We acknowledge the National Key R&D Program of China(2021YFA1501302)the National Natural Science Foundation of China(22121004,U1862207,22122808)+1 种基金the Haihe Laboratory of Sustainable Chemical Transformations(CYZC202107)the Program of Introducing Talents of Discipline to Universities(BP0618007)for financial support.
文摘Pentacoordinate Al^(3+)(Al^(3+)_(penta))sites on alumina(Al_(2)O_(3))could anchor and stabilize the active site over the cata-lyst surface.The paper describes the specific effect of Al^(3+)_(penta) sites on the structure and the catalytic performance of Al_(2)O_(3)supported Pt catalysts by modulating the quantity of Al^(3+)_(penta) sites.The Al^(3+)_(penta) site content of Al_(2)O_(3)exhibits a volcano-type profile as a function of calcination temperature due to the structural rearrangement.The loading of Pt and subsequent calcination can consume a significant portion of Al^(3+)_(penta) sites over the Al_(2)O_(3)support.We further find that,when the calcination temperature of the impregnated Al_(2)O_(3)is higher than the cal-cination temperature of Al_(2)O_(3)precursor,the structural rearrangement of Al^(3+)_(penta) sites could make Pt partially buried in Al_(2)O_(3).Consequently,this partially buried structure leads to relatively low conversion but high stability for propane dehydrogenation.This work further elucidates the stabilization mechanism of the Al^(3+)_(penta) site over Al_(2)O_(3)support.
基金supported by National Natural Science Foundation of China(grant no.21901196)the Natural Science Basic Research Plan in Shaanxi Province of China(grant nos.2020JQ-016 and 2021GXLH-Z-096)+1 种基金the Fundamental Research Funds for the Central Universities(grant no.xhj032021007-01)Xi’an Jiaotong University(grant no.71211920000001).
文摘A general method for the synthesis of bench-stable bis(difluoromethyl)pentacoordinate phosphoranes has been developed.The reaction is rapid,operationally simple,and easily scalable.The pentacoordinate phosphoranes can generate both difluoromethyl radical(·CF_(2)H)and difluorocarbene(:CF_(2))intermediates.Thus,a variety of fluoroalkylation transformations havebeen achieved by·CF_(2)H,such asoxidativedifluoromethylation of electron-deficient heterocycles,nickel/photoredox dual-catalyzed difluoromethylation of aryl bromides,and photoredox difluoromethylation of alkenes,or by:CF_(2),such as gem-difluorocyclopropanation of alkenes,base-promoted difluoromethylation of heteroatom nucleophiles,Pd-catalyzed difluoromethylation of arylboronic acids,and Cu-mediated trifluoromethylation of aryl iodides(via:CF_(2) and recombined CF_(3)-).These fluoroalkylation methods have been successfully applied to late-stage fluoroalkylation of drugs and drug-like molecules.
基金supported by Research Foundation for Advanced Talents of Inner Mongolia Normal University(2025YJRC005)the National Natural Science Foundation of China(12364038)+5 种基金the“Grassland Talents”project of the Inner Mongolia Autonomous Region(12000-12102613)the Young Science and Technology Talents Cultivation Project of Inner Mongolia University(21200-5223708)the Industrial Technology Innovation Projects of Inner Mongolia Academy of Science and Technology of China(2023JSYD01002)Science and Technology Plan Projects of Inner Mongolia Autonomous Region of China(2023KYPT0012)Key Project Funding from the Inner Mongolia Autonomous Region Natural Science Foundation(2023ZD27)High Level Introduction of Talent Research Start-up Fund(5909002405).
文摘Pursuing new two-dimensional(2D)materials has been a hot topic in materials science,driven by their potential for diverse applications.Recent research has unveiled stable planar hypercoordinate motifs with unconventional geometric arrangements and bonding patterns that facilitate the synthesis of new 2D materials with diverse applications.Among these,yet the design of 2D transition metal systems featuring planar pentacoordinate boron(ppB)is particularly intriguing.Here we address this gap by proposing a novel family of transition metal boride monolayers(MBenes)composed of ppB and heptacoordinate M motifs.The novelty of our MBenes stems from their distinct atomic arrangements and bonding configurations,setting them apart from traditional 2D materials.High-throughput calculations identified 10 stable MBenes(with the stoichiometry of MB,M=Cr,Fe,Co,Ni,Cu,Mo,Pd,Ag,Pt,Au)with exceptional thermodynamic,dynamic,thermal,and mechanical stabilities attributed to strong BB covalent bonds and MB ionic interactions.Notably,five of these MBenes(M=Ni,Pd,Pt,Ag,Au)hold high promise as topological superconducting materials with superconducting transition temperatures of 2.4-5.2 K.This discovery not only enriches the family of topological superconducting materials but also opens new avenues for quantum device development.Meanwhile,FeB monolayer exhibits robust ferromagnetic properties with a high Curie temperature of~750 K,which is particularly significant for spintronics applications.In addition,NiB and CuB MBenes demonstrate extremely low sodium diffusion barriers(about 30 and 90 meV)and high sodium storage capacities(788 and 734 mAh g1,respectively),making them promising anode materials for sodium-ion batteries(SIBs).This study expands the selection of electrode materials for SIBs and mitigates some existing limitations in battery technology.Overall,these findings underscore the multifunctional potential of MBenes,positioning them as transformative materials for quantum computing,spintronics,and energy storage applications.
基金Supported by the National Natural Science Foundation of China(No.20572061).
文摘Amino acid methyl ester phosphates were synthesized and determined by using positive-ion mode dectrospmy ionization mass spectrometry（ESIMS） in combination with multistage tandem mass spectrometry. The fragmentation pathways were investigated, and it was observed that most fragment ions contained the phosphoryl group. It was interesting to observe that the fragmentation pathways of the protonated molecule show some differences when compared with those of the sodium ion adduct. The methoxy group of amino acid methyl ester can migrate from the carbonyl group to the phosphoryl group in the sodium ion adduct.
基金support from the DFG research group 1497“Organic-Inorganic Nanocomposites through twin polymerization”.
文摘The syntheses of chiral pentacoordinated fluoridosilicates and their conversion into fluorine-doped silica and mesoporous carbon are reported.Starting from 4H,4’H-2,2’-spirobi[benzo[d][1,3,2]dioxasiline](1)and 8,8’-di-tert-butyl-4H,4’H-2,2’-spirobi[benzo[d][1,3,2]dioxasiline](2),the corresponding fluorido complexes 3 and 4 were obtained by the addition of potassium fluoride to the spirocyclic silicon salicylic alcoholates 1 and 2 in the presence of 18-crown-6.The pentacoordinated geometry around the silicon atom of the SiO_(4)F type in 3 and 4 was proved using single-crystal X-ray diffraction analysis.DSC measurements were used to study the thermal behavior of the compounds with regard to their usability in the twin polymerization process.Hence,polymerization of 3 and 4 and the simultaneous twin polymerization of the fluoridosilicate 3 with spirocyclic 1 gave fluorine-doped phenolic resin/silica composites as confirmed by solid state NMR spectroscopic studies(^(1)H,^(13)C{1H},^(19)F,and^(29)Si{1H}).Carbonization of the as-obtained hybrid materials and subsequent treatment with hydrofluoric acid resulted in microporous carbon with surface areas up to 1060 m^(2)g^(-1).Calcination of the hybrid materials produced fluorine-doped silica with BET surface areas up to 239 m^(2)g^(-1).Additionally,the synthesis of hybrid materials using the additive assisted twin polymerization of 1 with either tetra-n-butylammonium fluoride or KF gave either microporous carbon(1219 m^(2)g^(-1))or mesoporous silica(687 m^(2)g^(-1)).
基金supported from the National Key R&D Program of China(2022YFA1504500)the National Natural Science Foundation of China(92261207,21890752,and 22202164)for financial support+2 种基金support from the Natural Science Foundation of Fujian Province(2023J05006)the Fujian Provincial Chemistry Discipline Alliancethe Fundamental Research Funds for the Central Universities(20720230002)。
文摘The Pt Sn/Al_(2)O_(3)catalyst is commonly used in commercial propane dehydrogenation(PDH)processes,but it faces challenges in the deactivation and periodic regeneration due to metal aggregation and coke deposition at high temperatures.Although Al_(penta)^(3+)has been proven to be beneficial for enhancing catalytic stability,bottom-up synthesis protocols usually restrict their applications.Here,a facile post-treatment approach using acetic acid was applied to create color centers(electrons trapped within oxygen vacancies)onγ-Al_(2)O_(3).Notably,the content of Al_(penta)^(3+)was enriched to 18.3%.Then,the pre-established Pt Sn clusters were loaded.The electrons facilitated the formation of ultrafine Pt Sn nanoparticles(~2 nm),and the Al_(penta)^(3+)sites prevented the sintering of Pt Sn by constructing the strong Al_(penta)^(3+)–O–Sn bonds.Furthermore,the catalytic durability of the catalyst prepared by conventional impregnation methods was remarkably extended from 186 h for the color center-free sample to 1,000 h using the HAc–Al_(2)O_(3)support.This facile post-modification was further successfully extended to commercial Al_(2)O_(3)pellets without altering their mechanical properties,highlighting its potential in industrial applications.
基金financially supported by the National Natural Science Foundation of China(grant nos.52073137 and 51763018).
文摘Metal porphyrins are star molecules that possess welldefined coordination metal centers for versatile catalytic reactions.However,most previous work has focused on the correlations between in-plane symmetric configuration of metal-N_(4)sites and their catalytic performance.Addressing the catalytic contribution of additional axial coordination to such symmetric configuration remains a challenge.Theoretical calculations revealed that axially anchoring an extra pyridine on the tetra-coordinated cobalt porphyrin(Co-N4)to construct penta-coordinated cobalt porphyrin(Co-N_(5))renders cobalt a higher electron density,thereby favoring the rate-determining O_(2)adsorption/activation and reducing the oxygen electroreduction barrier.Therefore,a well-defined Co-N_(5)site is rationally introduced into the azo-linked polymer framework for a fundamental structure-catalytic performance correlation study.As-prepared Co-N_(5)catalyst exhibits a 26 mV positive shift in half-wave potential compared with the pyridine-free Co-N_(4)counterpart,discloses a markedly higher power density(141.4 mW cm^(−2)),and possesses better long-term durability(over 160 h cycles)in a Zn-air battery.Moreover,such a Co-N_(5)catalyst also showcases potential applications for CO_(2)reduction with high CO_(2)-to-CO conversion faradic efficiency and better selectivity than the Co-N_(4)counterpart because coordination of the fifth pyridine evokes electronic localization that suppresses a competitive side reaction.This work proves the positive electrocatalytic contribution of axial penta-coordination on well-defined metalporphyrin-based catalysts and offers atomic understanding of the structure-performance correlation on single atom catalysts for future catalyst design.
