查看更多>>摘要：Because of their unique structural and chemical properties,buckybowl molecules have attracted considerable attention in a wide range of scientific disciplines.The importance and utility of bucky-bowl molecules significantly increases once they acquire larger π-surface area and/or heteroatoms.The fusion of buckybowl molecules has emerged as a new strategy to extend the π-surface of polycyclic aromatic compounds;however,the π-extension of heteroatom-embedded buckybowls by the fusion strategy is still rare.Here we report the synthesis and propeties of a fused azacorannulene dimer bear-ing a C62N2 core(1a),which can also be regarded as a double aza[5]helicene.Due to the steric repulsion between two azapentabenzocorannulene moieties,this molecule shows a rigid S-shaped structure where the two azacorannulene bowls face in opposite direc-tions.Stepwise chemical oxidation of 1a resulted in the formation of the corresponding radical cation(1a+)and dication(1a2+),providing an important insight into their aromaticity.The fusion of heteroatom-embedded buckybowls provides a pow-erful way to synthesize π-extended polycyclic aro-matic molecules.
查看更多>>摘要：Revealing the molecular packing,intermolecular interac-tions,and aggregation behaviors in the nanocrystalline bulk heterojunction(BHJ)domains undertake the tasks for future materials design for efficient solar cells,especially in under-standing the structure-property relationship of isomeric non-fullerene acceptors(NFAs).Theoretical calculations re-veal that 2CIIC-β6,with β-and δ-chlorine-substituted terminal groups,achieves a relatively higher dipole moment for en-hanced intermolecular interactions.More importantly,when comparing the single-crystal X-ray diffraction patterns of three isomeric NFAs,BTIC-BO4CI-βδ,BTIC-BO4CI-βγ,and BTIC-BO4CI,the synergistic effect of chlorine atoms at theβ-and δ-positions endows BTIC-BO4CI-βδ better molecular planarity with a dihedral angle of 1.14°.In turn,this creates the shortest π…π distance(3.28 A)and smallest binding energies(-51.66 kcal mol1)of the three NFAs,resulting in the tightest three-dimensional network packing structure with a framework of Lx=14.0 A and Ly=13.6 A.Such a structure has multiple intermolecular interactions for better charge transfer.However,the chlorine atom at the y-position in the other two isomers contributes to non-intermolecular interactions with subordinate packing arrangements.Subse-quently,the red-shifted UV-absorption and higher electron mobility observed in neat films of BTIC-BO4CI-β6 agree well with its more ordered crystallinity.This leads to a more suitable fiber-like phase separation in the corresponding active blend,ultimately improving the device performance with superior charge transport.As a result,the highest power conversion efficiency of 17.04％with a current density of 26.07 mA cm-2 was obtained with the BTIC-BO4CI-βδ-based device.The carrier dynamics test and grazing inci-dence wide-angle X-ray scattering measurement indicate that the packing arrangement of molecules in the nanocrys-talline BHJ domains is consistent with their crystallinity.This work investigates the structure-property differences in three acceptors and emphasizes the effect of isomeric chlo-rine substitution,which suggests that changes in the crystal packing arrangement,especially the size of the framework,have a considerable influence on charge carrier transport and ultimately are reflected on the device efficiency elevation.
查看更多>>摘要：Development of high-efficiency electrode materials for the electrochemical CO2 reduction reaction(CO2RR)with high current density and selectivity compatible with industry is an important but signifi-cant challenge.Herein,we describe a facile strategy to enhance the selectivity and current density by regu-lating the local electron density of the cobalt site in a series of stable,conjugated,bimetallic Co/Zn poly-phthalocyanine frameworks CoxZnyPPc with an AB stacking model under alkaline aqueous conditions.When adjusting the ratio of Co and Zn to 3:1,the optimal Co3Zn1PPc exhibits an industry-compatible CO partial current density of 212 mA cm-2 at-0.9 V versus reversible hydrogen electrode in a flow cell,which is 1.7 and 9.1 times that of the single metal polyphthalocyanine CoPPc and ZnPPc,respectively.Co3Zn1PPc shows a high CO Faraday efficiency of more than 90％in a wide operating potential win-dow of-0.3 to-0.9 V.In-depth experimental and theoretical analysis revealed that introduction of electron-rich Zn atoms modified the electron densi-ty of the active Co center,placing Co in the electron-rich region and weakening the bonding strength with the reaction intermediate,thereby improving the CO2RR performance.These results clarify the interaction mechanism of dual metal sites at the atomic level and provide a new avenue for the de-sign of electrocatalysts with potential in industrial applications.
查看更多>>摘要：Herein,we report the synthesis and structures of two novel mixed-metal clusters denoted as Th9Ag6 and Th9Ag12.Both clusters feature unprecedented Th9 cores.The cores are tricapped trigonal prism moieties that are novel among actinides.Attempted alterna-tive synthesis routes indicate that the Th9 clusters are accessible only through slow introduction of Ag+into a solution containing a Th6 cluster modified with 2-picolinic acid.Alternative rapid addition of Ag+leads to dissociation of the Th6 cluster with formation of a high-purity(ThAg)∞ two-dimensional layered structure material.A mechanism for cluster dissocia-tion and reassembly to yield Th9 from Th6 is proposed that is consistent with spectroscopic observations and computational results.Because of Ag… Ag and π-π interactions,the Th9Ag12 cluster exhibits high stability in air,at elevated temperature,underγ-irradiation,and in common solvents.
查看更多>>摘要：Atomically precise gold and/or silver nanoclusters play a key role in crystallography and coordination chemistry.Compared with gold nanoclusters,silver nanoclusters become unstable and difficult to crystal-lize due to the high reactivity of metal silver.Herein,we report a silver nanocluster Ag213(Adm-S)44Cl33(Ag213)coprotected by bulky thiolates and chlorides.The low surface thiolate coverage(about 45％)endows Ag213 with high catalytic activity.Supported on activated carbon,Ag213 nanoclusters exhibit excellent electro-catalytic oxygen reduction performance with Eonset and E1/2 values of 0.89 and 0.72 V,respectively,close to the values of commercial Pt/C catalyst.This is the first report on the electrocatalytic oxygen reduction reaction of nanoclusters with more than 100 silver atoms.Ag213 with the diameter of 2.75 nm comprises a core-shell structure Ag7@Ag32@Ag77@Ag97.The strong plasmonic absorption band at 454 nm reveals the metallic nature of Ag213.Interestingly,halide is of importance.Chloride facilitates the formation of Ag213 and Ag56(Adm-S)33CI16(Ag56Cl)while bromide can promote the formation of Ag56(Adm-S)33Br16(Ag56Br).This work provides an example for the study of large-sized metal nanoclusters and nanocluster-based elec-trocatalysts.
查看更多>>摘要：Electronic and bonding situations at reaction centers are often detected by the remote substituent effect.For nonorganometallic reactions,this effect is conven-tionally described by the well-known Hammett-type substituent constants.However,for most transition metal(TM)-involved systems,no analogous numeral descriptors reflecting the intrinsic differences be-tween metallic and nonmetallic bonding have been rigorously established till present.Herein,we report a Pd(Ⅱ)-O bond heterolysis energy △Ghet(Pd-O)study of the archetypal palladium complexes to represent the thermodynamics of the essential bond-breaking step in Pd-mediated transformations.Meanwhile we furnish the new substituent constants σPd+s and there-from facilitate linear free-energy relationship(LFER)analysis for Pd-catalyzed reactions.Indeed,this led us to find an unexpected electron-donating ability of Pd(Ⅱ)cation,which provided a gifted experimental support,with the aid of computation,to attribute the frustrating observation of a much scattered curvature in the △Ghet(Pd-O)-σ+correlation to the electron-donating capacity of the cationic palladium through back-donation of its d-electrons.Applications of LFER analysis with σPd+to predict the redox behavior of the palladium complex and in a kinetics vs.thermodynam-ics mechanistic study of transmetalation added further credence to their applicability to TM systems.
查看更多>>摘要：Single-atom catalysts(SACs)are gaining increasing recognition because of their superior catalytic prop-erties for various reactions.However,the performance of SACs is often limited by the lack of neighboring metal centers to cooperate in catalysis.Herein,a synergetic interaction between neighboring Cu atoms of a few-atom catalyst(FAC)on graphdiyne(GDY)is found to greatly enhance the production of acetate in the CO electroreduction reaction relative to Cu SACs.In a 1.0 M KOH electrolyte,this Cu FAC exhibits an acetate Faradaic efficiency of 53.8±1.5％,an ultrahigh relative purity of up to 97 wt％for liquid products,and excellent stability over 23 h continuous electrolysis at-0.8 V versus reversible hydrogen electrode.Theoret-ical studies suggest that the intersite catalytic com-munication between two neighboring metal atoms confined in each pore of GDY facilitates the formation of acetic acid through either stepwise hydrogenation of CH2CO*or the direct reaction of H2O with CH2CO*.Our study demonstrates the unprecedented synerget-ic catalysis of Cu FAC in promoting the selective CO electroreduction toward acetate production.
查看更多>>摘要：Enormous LiFePO4(LFP)/graphite batteries retired from the market need urgent rational disposal and reutilization based on the degradation analysis of the evolutional mechanism for electrodes.Typically,Li inventory loss is one of the main reasons for the degradation of LFP-based batteries.The reduced portion of lithium in a cathode is inevitably consumed to form solid electrolyte interphase or trapped in the anode.Herein,we propose a comprehensive strategy for battery recycling and conduct the work by simply regenerating the degraded LFP materials directly with the extracted lithium compounds from spent anodes.Moreover,inter-particle three-dimensional(3D)conductive networks are built via an in situ carbonization to reinforce the electronic conductivity of regenerated cathodes.An improved electrochem-ical performance was achieved in the regenerated LFP materials even compared with the pristine LFP.This integrated recycling strategy not only brings more added value to the recycled materials by leveraging the recycling process but also aims to apply the concept of"treating waste with waste"and spur innovations in battery recycling technologies in the future.
查看更多>>摘要：The inevitable ion migration that occurs within ionic polycrystalline perovskite film results in inferior long-term stability of perovskite solar cells(PVSCs)that cannot meet the commercial requirements.Here,a novel poly(ionic liquid)named poly-1-vinyl-3-propyl-trimethoxysilane imidazolium chloride(PImIL-SiO)is first introduced into perovskite to strengthen grain boundaries(GBs)and construct dual-functional bar-riers against internal ion migration and external mois-ture erosion for fabricating highly efficient and stable PVSCs.PImlL-SiO-containing imidazolium cations and pendant siloxane groups contribute to passivation of bulk defects and anchoring of GBs,which effectively hinders ion migration channels,thus reducing perov-skite film phase separation and device hysteresis.Furthermore,the intrinsically hydrophobic PImlL-SiO automatically forms a secondary protective barrier to endow the perovskite film with ultrahigh moi-sture corrosion resistance through the hydrolyzation reaction of siloxane with the permeated moisture.Consequently,the PImIL-SiO-modified PVSCs achieve a champion power conversion efficiency(PCE)of 22.46％,accompanied by excellent thermal and humid-ity stabilities where the non-encapsulated devices re-tain 87％of the initial PCE after aging at 85 ℃ for 250 h and＞85％of the initial PCE over 1100 h in air with a relative humidity of 50-70％.
查看更多>>摘要：Supported metal catalysts integrating advantages of catalytic hydrogenation and stoichiometric reduction are highly desirable for the green production of fine chemicals.Decoupling catalytic hydrogenation into H2 activation and selective reduction taking place at different locations is expected to provide an effective strategy to fabricate such catalyst systems.Herein,we report a decoupled hydrogenation system by modify-ing Pt catalysts supported on reducible ln203 with ethylenediamine(EDA).The system exhibits good catalytic performance in oximes production from nitroalkanes,an industrially important reaction,by employing H2.Systematic studies demonstrate that the surface coordination of EDA on Pt is crucial to passivate the Pt surface from nitro hydrogenation without inhibiting H2 activation.The activated H2 species can then transfer and reduce the ln203 sup-port in situ to generate sustainable stoichiometric reducing agents for the chemoselective reduction of nitroalkanes.Based upon the mechanistic under-standing,a sustainable strategy for the production of oximes has been successfully fabricated.
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