Design of bifunctional single-atom catalysts NiSA/ZIF-300 for CO_(2) conversion by ligand regulation strategy

Carbon-supported noble-metal-free single-atom catalysts(SACs)have aroused widespread interest due to their green chemistry aspects and excellent performances.Herein,we propose a“ligand regulation strategy”and achieve the successful fabrication of bifunctional SAC/MOF(MOF=metal-organic framework)nanocomposite(abbreviated NiSA/ZIF-300;ZIF=ZIF-8)with exceptional catalytic performance and robustness.The designed NiSA/ZIF-300 has a planar interfacial structure with the Ni atom,involving one S and three N atoms bonded to Ni(Ⅱ),fabricated by controllable pyrolysis of volatile Ni-S fragments.For CO_(2) cycloaddition to styrene epoxide,NiSA/ZIF-300 exhibits ultrahigh activity(turnover number(TON)=1.18×105;turnover frequency(TOF)=9830 molSC·mol_(Ni)^(-1)·h^(-1);SC=styrene carbonate)and durability at 70℃ under 1 atm CO_(2) pressure,which is much superior to Ni complex/ZIF,NiNP/ZIF-300,and most reported catalysts.This study offers a simple method of bifunctional SAC/MOF nanocomposite fabrication and usage,and provides guidance for the precise design of additional original SACs with unique catalytic properties.

Covalence bridge atomically precise metal nanocluster and metalorganic frameworks for enhanced photostability and photocatalysis

Metal nanoclusters(NCs)with precise structure and ultrasmall size have attracted great interests in catalysis.However,the poor stability has limited its large-scale use.Herein,we proposed the“covalence bridge”strategy to effectively connect atomically precise metal NCs and metal-organic frameworks.Benefiting from the covalent linkage,the synthesized UiO-66-NH2-Au25(LCys)18 showed outstanding stability after 16 h photocatalysis.Moreover,the covalence bridge created a strong metal-support interaction between the two components and provided an effective charge transport channel and thereby enhanced photocatalytic activity.UiO-66-NH2-Au25(L-Cys)18 displayed an exceptional photocatalytic H2 production rate,which is 21 and 90 times higher than that of UiO-66-NH2/Au25(PET)18(made by physically combination)and bare UiO-66-NH2,respectively.Thermodynamic and kinetic studies demonstrated that UiO-66-NH2-Au25(L-Cys)18 exhibited higher charge transfer efficiency,lower overpotential of water reduction and activation energy barrier compared with its counterparts.

Atomically precise coreless AuCu bimetallic nanoclusters for Ullmann C-O coupling

Bimetallic nanocluster with atomic precision has gained widespread attention due to its unique synergism.The coreless Au_(4)Cu_(5)bimetallic nanoclusters were selected as models to explore the relationship between their microstructure and performance,and compare with the coreless monometallic nanoclusters,core–shell nanoclusters,and single atom catalyst(SAC).The experimental results show that the coreless bimetallic nanocluster catalyst Au_(4)Cu_(5)/activated carbon(AC)exhibits high activity and stability in the Ullmann C–O coupling reaction,much higher than coreless monometallic nanoclusters(Au_(11)/AC and Cu_(11)/AC),core–shell nanoclusters(Au_(25)/AC,Cu_(25)/AC,and Au_(1)Cu_(24)/AC),and single atom catalysts(Au SAC and Cu SAC).Moreover,the coreless Au_(4)Cu_(5)/AC catalyst efficiently catalyzed the Ullmann C–O coupling of benzyl alcohol for the first time.This structure–activity relationship was successfully extended to other coreless bimetallic systems,such as Au_(4)Cu_(4)/AC nanocluster,and it is expected to provide new insights for the design of bimetallic catalysts with well-defined performance.

CW-YOLO: joint learning for mask wearing detection in low-light conditions

1 Introduction With the rapid progress of Artificial Intelligence(AI)technology in object detection and face recognition,deep learning methods for face mask wearing detection have become increasingly mature and continuously take into account the needs of efficiency and accuracy.However,these conventional detection methods mostly ignore the complexity of real-world application scenarios,such as extremely darkness and gloomy weather.These unfavorable conditions lead to a series of image degradations that seriously hamper machine vision tasks.Although camera parameter adjustment,auxiliary lighting,or pre-processing enhancement[1]can weaken these negative effects to some extent to promote the detection,they will also result in increased hardware and time costs.

Exposing Cu-rich {110} active facets in PtCu nanostars for boosting electrochemical performance toward multiple liquid fuels electrooxidation

In catalysis,tuning the structural composition of the metal alloy is known as an efficient way to optimize the catalytic activity.This work presents the synthesis of compositional segregated six-armed PtCu nanostars via a facile solvothermal method and their distinct composition-structure-dependent performances in electrooxidation processes.The alloy is shown to have a unique six arms with a Cu-rich dodecahedral core,mainly composed of {110} facets and exhibit superior catalytic activity toward alcohols electrooxidation compared to the hollow counterpart where Cu was selectively etched.Density functional theory (DFT) calculations suggest that the formation of hydroxyl intermediate (OH^*) is crucial to detoxify CO poisoning during the electrooxidation processes.The addition of Cu is found to effectively adjust the d band location of the alloy catalyst and thus enhance the formation of ^*OH intermediate from water splitting,which decreases the coverage of ^*CO intermediate.Our work demonstrates that the unique compositional anisotropy in alloy catalyst may boost their applications in electrocatalysis and provides a methodology for the design of this type catalyst.

Monodispersed Au Pd nanoalloy: composition control synthesis and catalytic properties in the oxidative dehydrogenative coupling of aniline

A series of Au Pd@C nanoalloy catalysts with tunable compositions were successfully prepared by a co-reduction method. The use of borane-tert-butylamine complex as reductant and oleylamine as both solvent and reductant was very effective for the preparation of the monodispersed nanoalloy. We evaluated the catalytic activity of these Au Pd@C nanoalloys for oxidative dehydrogenative coupling of aniline, which showed better catalytic activity than equal amounts of sole Au@C or Pd@C catalyst. The Au1Pd3@C catalyst exhibited the best performance, indicating that the conversion and selectivity were improved along with the increase of Pd composition. However, if the Pd composition was too high in the Au Pd alloy, Au1Pd7@C achieved only 81% conversion in this reaction.