Synthesis,Structure and Characterization of a 3D Chiral Carboxylate and Phosphonate Metalorganic Framework Based on 1,1?-Biphenol Ligand

A novel phosphonate-based chiral metal-organic framework 1 was synthesized from C2-symmetric 1,1？-biphenol-based ligand and structurally characterized by single-crystal and powder X-ray diffraction, Fourier-transform infrared spectra（FTIR）, circular dichroism（CD） and thermogravimetric analyses（TGA）. Two neighboring Mn ions are linked by two carboxylate groups and one phosphate group to form a di-manganese unit [Mn2] and each [Mn2] cluster in 1 is linked by five ligands, generating a 3D network with fns topology. In addition, the photoluminescence properties of 1 and H4 L were investigated.

Synthesis,Structure and Characterization of a 3D Chiral Indium Carboxylate Metal-organic Framework Based on 1,1'-Biphenol Ligand

A novel indium-based chiral metal organic-framework 1 {In2L（μ2-O）（H2O）3}n was synthesized from C2-symmetric 1,1？-biphenol-based ligand H4 L and structurally characterized by single-crystal and powder X-ray diffraction, Fourier-transform infrared spectra（FTIR）, solid-state circular dichroism（CD） and thermal gravimetric analysis（TGA）. 1 crystallizes in monoclinic space group P21 with a = 10.1861（5）, b = 18.5632（9）, c = 16.5153（8） A^°, V = 3077.1（3） A^°^3, Z = 2, Mr = 944.29 g/mol, Dc = 1.019 g/cm^3, F（000） = 944, GOOF = 0.932, the final R = 0.0577 and w R = 0.1091 for 22090 observed reflections with I 〉 2σ（I）. Each In2 cluster in 1 is linked by four ligands and each ligand is coordinated to four In2 clusters to generate a 3D network. Additionally, the photoluminescence of 1 and H4 L were also investigated.

A Novel TADDOL-based Chiral Metal-organic Framework：Synthesis, Structure and Photoluminescence Study

A new C2-symmetric TADDOL-based ligand H4L was designed and synthesized from readily available tartaric acid and was used to construct a novel TADDOL-based chiral metal-organic framework {[Co2L（DMA）（H2O）5]·2DMA}n 1（DMA = N,N-dimethylacetamide）. It was characterized by single-crystal and powder X-ray diffraction, Fourier-transform infrared spectra（FTIR）, solid-state circular dichroism（CD） and thermal gravimetric analysis（TGA）. 1 crystallizes in the chiral orthorhombic space group P212121 with a = 9.7060（8）, b = 15.5661（1）, c = 44.564（3） , V = 6732.9（9） -3, Z = 4, Mr = 1394.08, Dc = 1.375 g/cm-3, F（000） = 2888, GOOF = 1.032, the final R = 0.0607 and wR = 0.1582 for 21374 observed reflections with I 〉 2σ（I）. Each Co2 cluster in 1 is linked by three ligands and each ligand is coordinated to three Co2 clusters with one free carboxylate group, thus generating a 2D network. These 2D networks are further extended into a 3D supramolecule framework by the hydrogen bonding interactions（O–H…O） in an A-B-A-B stacking mode. Additionally, the photoluminescence of 1 and H4L were also investigated.

Chiral transfer amidst one-dimensional linear polymers and twodimensional network covalent organic frameworks:Striking a fine balance between helicity and crystallinity

The current landscape of chiral covalent organic frameworks(COFs)predominantly centered on constructing asymmetric molecular-scale chirality,often introducing an inherent contradiction to the COF symmetry and limiting diversity.Herein,we overcome these challenges by achieving chiral transfer between one-dimensional(1D)imine linear polymers(LPs)and two-dimensional(2D)networkβ-ketoenamine COFs composed of achiral monomers.We successfully synthesize several 1D imine LPs with mesoscopic helical chirality,comprising achiral C2-symmetric terephthalaldehyde and diamine linkers in a chiral supramolecular transcription system.Leveraging the irreversible tautomerism mechanism within the linker replacement approach,terephthalaldehyde(TPA)units in these helical 1D LPs are substituted with C3-symmetric 1,3,5-triformylphloroglucinol(TP),yielding the corresponding 2D networkβ-ketoenamine COFs.Crystallinity and helicity of the resultantβ-ketoenamine COFs intimately hinge on reaction conditions,including the aldehyde stoichiometry of Tp and TPA,as well as the quantity and concentration of the catalyst employed.Under optimized conditions,the nucleation and growth were precisely governed,achieving a harmonious equilibrium of crystallinity and helicity within the generated 2D networkβ-ketoenamine COFs,even with covalent bond rupture,recombination,and topological transition(from[C2+C2]to[C3+C2]).Impressively,the ground state chirality inherent to helical 1D LPs seamlessly transfers to helical 2D networkβ-ketoenamine COFs.This study not only offers new perspectives on the development of chiral functional COFs,but also provides fresh insights into the precise control of COFs'microscopic morphology.

Amplified circularly polarized luminescence of chiral metal-organic frameworks via post-synthetic installing pillars

Post-synthetic installation strategy is an effective approach to improve the functions of metal-organic frameworks(MOFs).Herein,a pair of chiral MOFs is successfully constructed through solvothermal subcomponent self-assembly and exhibit circularly polarized luminescence(CPL).These MOFs contain coordinatively unsaturated Zn sites and channels,which allow the installation of pyridyl-terminated pillars into the original structure.Such a post-synthetic installation process reinforces the MOFs'rigidity and increases the photoluminescence quantum yields(PLQYs).Furthermore,the luminescence dissymmetry factors(glum)of these post-modified MOFs are amplified after installing the pillars.This work provides an appealing strategy for boosting the CPL performance of chiral MOFs.

Chiral metal-organic frameworks-based materials for chromatographic enantioseparation

The homochiral compounds play an important role in human health and pharmaceutical industry.Currently,the chromatographic enantioseparation has become one of the most effective and practical approach to obtain pure enantiomers.Herein,the exploration of advanced materials,using as chromatographic chiral stationary phases for racemic separation,has attracted great attention.Thanks to their high enantioselectivity and controllable synthesis,the emerging chiral metal-organic frameworks (CMOFs)have been widely studied as the stationary phase in chromatographic technology.In this review,we will summarize the principles of synthetic strategies and mechanism of chiral microenvironment.In particular,the recent progress and research hotspot of CMOFs regarding as the chiral stationary phases in gas chromatography (GC),high-performance liquid chromatography (HPLC),and capillary electrochromatography (CEC),are elucidated systematically according to the published work.Last but not the least,we also highlight the challenges and perspectives of rational design of CMOFs,as well as their corresponding racemic separation.We envision that the review will provide a further understanding of CMOFs and facilitate the development of chromatographic enantioselective applications.

Stable hydrazone-linked chiral covalent organic frameworks:Synthesis,modification,and chiral signal inversion from monomers

The designed synthesis of chiral covalent organic frameworks(COFs) featuring intriguing properties is fairly scant and remains a daunting synthetic challenge.Here we develop a de novo synthesis of an enantiomeric pair of 2 D hydroxyl-functionalized hydrazone-linked chiral COFs,(S)-and(R)-HthBta-OH COFs,using enantiopure 2,5-bis(2-hydroxypropoxy)terephthalohydrazide(Hth) as monomers.The fo rmation process of hydroxyl-functionalized chiral COFs was monitored using rigorous time-dependent PXRD,vibrational circular dichroism(VCD),and electronic circular dichroism(ECD) studies.Remarkably,VCD spectra indicated a unique chiral signal inversion from the positive Cotton effect of(S)-Hth monomer to the negative Cotton effect of(S)-HthBta-OH COF,which has never been reported in chiral COFs.Moreover,two unprecedented carboxyl-functionalized chiral COFs,(S)-and(R)-HthBta-COOH,were constructed by a post-synthetic modification of the corresponding hydroxyl chiral COFs with succinic anhydride.Notably,carboxyl-functionalized COFs retained homochirality and crystallinity without linker racemization and structural collapse after the chemical modification due to the chemically robust nature of pristine hydrazone-linked chiral COFs.

Electrochemical Chiral Recognizing Tryptophan Enantiomers Based on Chiral Metal-Organic Framework D-MOF

In this work,an electrochemical chiral sensor of a nanowire-like chiral metal-organic framework/multiwalled carbon nanotube-chitosan/glassy carbon electrode(D-MOF/MWCNTs-CS/GCE)was proposed for the enantiorecognition of L/D-tryptophan(L/D-Trp).The asymmetrical spatial structure of D-MOF provides the feasibility for the enantiorecognition of Trp enantiomers.Moreover,differential pulse voltammetry(DPV)was carried out to be the detection method and the DPV peak potential difference(ΔEp)between L-Trp and D-Trp was referred as the index of the enantiorecognition performance.Several parameters,such as mass ratios and drop-coated volume of MWCNTs-CS,drop-coated volume and concentration of D-MOF,pH and detection temperature of D-MOF/MWCNTs-CS/GCE were optimized for the largestΔEp value.And the molecular dynamics(MD)simulation was used to elucidate the enantiorecognition mechanism.Furthermore,the proportions of D-Trp(D-Trp%)in Trp mixtures were detected in a good linear relationship with the DPV peak potentials(Ep),and the proposed electrochemical chiral sensor exhibited good reproducibility,stability and enantiorecognition ability.Additionally,the proposed electrochemical chiral sensor(D-MOF/MWCNTs-CS/GCE)has a good application prospect in the fields of biomedicine,clinical diagnosis,chemical production,pharmaceuticals safety and so on.