Facile synthesis of ultrathin metal-organic framework nanosheets for Lewis acid catalysis

Ultrathin metalorganic framework (MOF) nanosheets are attracting great interest in catalysis due to their unique and intriguing two-dime nsional (2D) features. Although many progresses have been achieved, it is still highly desirable to develop novel strategies for controllable synthesis of the well-defined ultrathin MOF nanosheets. Herein we report a polyvinylpyrrolidone (PVP)-assisted route to synthesize the ultrathin Ni-MOF nanosheets characteristic of 1.5 nm in thickness, in which PVP is reacted with 2-aminoterephthalic acid (H2BDC-NH2) via formation of C=N bon d, followed by coord inatio n with Ni2+ io ns to form the ultrathi n MOF n anosheets. Impressively, when used in the Kno eve nagel condensation reactions of propane dinitrile with different aldehydes, ultrathin Ni-MOF nanosheets display the significantly enhanced catalytic activity and good stability in respect with the bulk Ni-MOF, mainly owing to the exposed active sites as well as facile mass transfer and diffusion of substrates and products.

Structure regulated catalytic performance of gold nanocluster-MOF nanocomposites

Atomically precise gold(Au)nanoclusters(NCs)as visible light photosensitizers supported on the substrate for photoredox catalysis have attracted considerable attentions.However,eficient control of their photocatalytic activity and long-term stability is still challenging.Herein,we report a coordination-assisted self-assembly strategy in combination with electrostatic interaction to sandwich Au2:(Capt)18(abbreviated as AU25,Capt=captopril)NCs between an inner core and an outer shell made of UiO-66,denoted as UiO-66@Au25@UiO-66.Notably,the sandwich-like nanocomposite displays significantly enhanced catalytic activity along with an excellent stability when used in the selective photocatalytic aerobic oxidation of sulfide to sulfoxide.As comparison,AU25 NCs simply located at the outer surface or insider matrix of UiO-66(short as Au2/UiO-66 and AU2s@UiO-66)show poor stability and low conversion,respectively.This structure regulated difference in the catalytic performances of three nanocomposites is assigned to the varied distribution of active sites(Au NCs)in metal-organic frameworks(MOFs).This work offers the opportunity for application of nanoclusters in catalysis,energy conversion and even biology.

Photocatalytic Carboxylation of Phenyl Halides with CO_(2) by Metal-Organic Frameworks Materials

In this work,important commercial pharmaceutical intermediates,phenylpropionic acid compounds,are successfully obtained by catalyzing the reaction of carbon dioxide with phenyl halides using MOF-5,a typical metal-organic framework(MOF)material.The influence of temperature,pressure,catalyst type and light on the reaction is investigated,and a 90.3%selectivity towards fluorophenylpropionic acid is reached.Significantly,the catalysts are effective for varied benzyl compounds containing different substituent groups.The catalysts are stable and remain active after three cycles.

Single site catalyst with enzyme-mimic micro-environment for electroreduction of CO_(2)

Single site catalysts provide a unique platform for mimicking natural enzyme due to their tunable interaction between metal center and coordinated ligand.However,most works have focused on preparing structural and functional models of nature enzyme,with less reports also taking the local chemical environment,i.e.,functional/catalytic residues around the active site which is an essential feature of enzymes,into consideration.Herein,we report a Co-centered porphyrinic polymer containing the enzyme-mimic micro-environment,where the linker triazole over CoN4 site enables formation of hydrogen bond with the*COOH intermediate,thus promoting the electrocatalytic reduction of CO_(2).As-prepared catalyst achieves the CO_(2)-to-CO conversion of 5,788 h^(−1) turnover frequency value and near unit(~96%)faradaic efficiency at−0.61 V versus reversible hydrogen electrode.This strategy will bring new dimension of designing highly active single-site catalysts.

Optical Activity of Chiral Metal Nanoclusters

CONSPECTUS:The emerging chirality in nanomaterials represents one of the most dynamic areas in modern science.Although many novel chiral nanomaterials have been reported,the origin of their chirality and related optical activity have been not unveiled unambiguously.Thanks to the fast development of noble metal cluster chemistry,the structures of many chiral nanoclusters(CNCs)have been precisely determined and their chirality origin has been decoded as four different levels including chiral ligand,helix staple motif,asymmetry metal kernel,and chiral arrangement of organic ligands.Generally,the strong optical activity associated with the electron transitions of the noble metal core is popularly reported among CNCs protected by chiral ligands,following the so-called“outside-in”chirality transfer theory,namely,from organic ligand to metal core.Exceptionally,inherent chiral structures are discerned inside CNCs consisting of achiral ligands,such as the helix staples found in Au38(SR)24 and Au102(SR)44(SR=thiolate)and the chiral metal kernel existing in Au20(PP3)4Cl4(PP3=tris(2-(diphenylphosphino)ethyl)phosphine).These chiral nanostructures induce distinct optical activity and even present reversed chirality transformation in the case of Au38(SR)24(i.e.,from chiral core structure to organic ligand).In the past decade,our group has carried out extensive research work on preparation,enantioseparation,optical activity,and application of chiral inorganic nanostructures.As representatives,enantiopure right-handed and left-handed Au20(PP3)4Cl4 clusters of intrinsic kernel chirality were acquired through an innovative supramolecular self-assembly method and their circular dichroism(CD)feature involving only the metal core was systematically studied;Au3[R/S-Tol-BINAP]3Cl(R/S-Tol-BINAP:R/S-2,2′-bis(di-p-tolylphosphino)-1,1′-binaphthyl)clusters with the smallest metal-atom number among the reported CNCs were designed and synthesized by using the privileged chiral Tol-BINAP ligand,which exhibited not only strongly enhanced CD signal also remarkable circular polarized luminescence(CPL)response as selfassembled into monodispersed nanocubes.In this Account,we aim at reviewing the fast development of CNCs featuring strong chiral attributes and optical activity.We will briefly introduce the preparation methods of CNCs,such as direct synthesis,ligand exchange,and enantioseparation.In the following parts,the commonly used tools for characterizing the chirality of CNCs are summarized,including CD,vibrational circular dichroism(VCD),CPL,single X-ray diffraction,nuclear magnetic resonance(NMR),and theoretical prediction.Then,the optical activity of CNCs will be systematically discussed,especially their CD,VCD,and CPL activity along with their chirality origin.Finally,future strategies for fabricating CNCs possessing strong optical activity as well as potential chirality-related applications will be proposed.We believe that this Account will trigger more research interest to not only study the amazing optical activity of CNCs but also employ them in many fields.