A Fluorine-Functionalized 3D Covalent Organic Framework with Entangled 2D Layers

Constructing three dimensional(3D)covalent organic frameworks(COFs)through the entanglement of two dimensional(2D)nets is a promising but underdeveloped strategy.Herein,we report the design and synthesis of a fluorine functionalized 3DCOF(3D-An-COF-F)formed by entangled 2D sql nets.The structure of 3D-An-COF-F was determined by the combination of continuous rotation electron diffraction technique and modelling based on the chemical information from real space.Interestingly,compared to the isostructural 3D-An-COF without F atom s,3DAn-COF-F showed an improved CO_(2)sorption ability and higher CO_(2)/N_(2)selectivity.Our study not only demonstrated the generality of constructing 3D COFs with entangled 2D nets by introducing bulky groups vertically in planar building blocks,but also will expand the diversity of 3D COFs for various applications.

High-sensitivity shortwave infrared photodetectors of metal-organic frameworks integrated on 2D layered materials

Photodetectors operating in the shortwave infrared region are of great significance due to their extensive applications in both commercial and military fields.Narrowbandgap two-dimensional layered materials(2DLMs)are considered as the promising candidates for constructing nextgeneration high-performance infrared photodetectors.Nevertheless,the performance of 2DLMs-based photodetectors can hardly satisfy the requirements of practical applications due to their weak optical absorption.In the present study,a strategy was proposed to design high-performance shortwave infrared photodetectors by integrating metalorganic frameworks(MOFs)nanoparticles with excellent optical absorption characteristics and 2DLM with high mobility.Further,this study demonstrated the practicability of this strategy in a MOF/2DLM(Ni-CAT-1/Bi_(2)Se_(3))hybrid heterojunction photodetector.Due to the transfer of photo-generated carriers from the MOF to Bi_(2)Se_(3),the MOF nanoparticles integrated on the Bi_(2)Se_(3) layer can increase the photocurrent by 2-3 orders of magnitude.The resulting photodetector presented a high responsivity of 4725 A W^(−1) and a superior detectivity of 3.5×10^(13) Jones at 1500 nm.The outstanding performance of the hybrid heterojunction arises from the synergistic function of the enhanced optical absorption and photogating effect.In addition,the proposed device construction strategy combining MOF photosensitive materials with 2DLMs shows a high potential for the future high-performance shortwave infrared photodetectors.

Synthetic Strategies for Constructing Two-Dimensional Metal-Organic Layers （MOLs）： A Tutorial Review

Two-dimensional （2D） metal-organic layers （MOLs） are the 2D version of metal-organic frameworks （MOFs） with nanometer thickness in one dimension. MOLs are also known as 2D-MOFs, 2D coordination polymers, ultrathin MOF nanosheets （UMOFNs） or coordination nanosheets in literature. This new category of 2D materials has attracted a lot of interests because of the opportunity in combining molecular chemistry, surface/interface chemistry and material chemistry of low dimensional materials in these systems. Several synthetic strategies have been developed for the construction of 2D MOLs, but the general synthesis of MOLs still presents a challenge. This tutorial level review summarizes the recent progress in the fabrication of novel 2D MOLs and aims to highlight challenges in this field.

Probing surface structure on two-dimensional metal-organic layers to understand suppressed interlayer packing

Two-dimensional metal-organic layers(MOLs)from alternatively connected benzene-tribenzoate ligands and Zr6(μ3-O)_(4)(μ3-OH)_(4) or Hf6(μ3-O)_(4)(μ3-OH)_(4) secondary building units can be prepared in gram scale via solvothermal synthesis.However,the reason why the monolayers did not pack to form thick crystals is unknown.Here we investigated the surface structure of the MOLs by a combination of sum-frequency generation spectroscopy,nanoscale infrared microscopy,atomic force microscopy,aberration-corrected transmission electron microscopy,and compositional analysis.We found a partial coverage of the monolayer surface by dangling tricarboxylate ligands,which prevent packing of the monolayers.This finding illustrates low-density surface modification as a strategy to prepare new two-dimensional materials with a high percentage of exposed surface.

Non-3d metal modulated zinc imidazolate frameworks for CO_(2) cycloaddition in simulated flue gas under ambient condition

Cycloaddition of CO_(2) and epoxide into cyclic carbonate is one of the most efficient ways for CO_(2) conversion with 100% atom-utilization. Metal–organic frameworks are a kind of potential heterogeneous catalysts, however, high temperature, high pressure, and high-purity CO_(2) are still required for the reaction.Here, we report two new Zn(Ⅱ) imidazolate frameworks incoporating MoO_(4)^(2–)or WO_(4)^(2–)units, which can catalyse cycloaddition of CO_(2) and epichlorohydrin at room temperature and atomospheric pressure, giving 95% yield after 24 h in pure CO_(2) and 98% yield after 48 h in simulated flue gas(15% CO_(2)+ 85% N_(2)),respectively. For comparison, the analogic Zn(Ⅱ) imidazolate framework MAF-6 without non-3d metal oxide units showed 71% and 33% yields under the same conditions, respectively. The insightful modulation mechanisms of the MoO_(4)^(2–)unit in optimizing the electronic structure of Zn(Ⅱ) centre, facilitating the rate-determined ring opening process, and minimizing the reaction activation energy, were revealed by X-ray photoelectron spectroscopy, temperature programmed desorption and computational calculations.

Porous N-doped-carbon coated CoSe2 anchored on carbon cloth as 3D photocathode for dye-sensitized solar cell with efficiency and stability outperforming Pt

Photocathode with superior catalytic activity,long-term stability,and fast mass/electron transfer is highly desirable but challenging for dye-sensitized solar cell(DSC).Herein,the ZIF-67 grown on carbon cloth is successfully transformed into CoSe2 embedded in N-doped carb on nano cage(CoSe2/N-C)via a growth-carbonization-selenization process.The carb on cloth supported CoSe2/N-C,as photocathode of DSC,demonstrates a good long-term stability and high photovoltaic efficiency(8.40%),outperforming Pt.The good efficiency can be attributed to the high catalytic activity of CoSe2,fast mass tran sfer of porous three-dimensi on al(3D)structure,and good electr on transport derived from the intimate con tact between CoSe2 and highly conductive carb on cloth.The high stability would be ascribed to N-doped carbon coating that perfectly prevents CoSe2 from decomposition.This work will pave the way to develop highly efficient and stable Pt-free photocathode for DSC.

Three New Isostructural Metal-organic Coordination Polymers from Triangular Pyridinedicarboxylate Ligand:Syntheses, Structures and Properties

Three new isostructural coordination polymers,namely,[Mg(cpna)(H2O)2]n(1),[Mn(cpna)(H_(2)O)_(2)]n(2)and[Co(cpna)(H_(2)O)_(2)]n(3)(H_(2) cpna=5-(3-carboxylphenyl)nicotic acid)are reported.They were synthesized by hydrothermal reactions of transition metal or alkaline earth metal chloride with 5-(3-carboxylphenyl)nicotic acid,respectively.Complexes 1~3 exhibit 2D layers with a 3,3-connected topology with Schl?fli symbol{4.82}.Such layers including hexagonal rings and a quadrangular ring are further extended into an ordered 3D framework by hydrogen bonds between the cpna2-ligands and water molecules.The rare complex 1 has excellent luminescence and can be used as luminescent materials,while 2 and 3 possess prominent magnetism with potential applications in magnetic materials.

Structures and Properties of Two New Three-Dimensional Inorganic-Organic Hybrid Compounds Based on Isopolymolybdate Clusters

Two new inorganic-organic hybrid materials containing different isopolymolybdate units, namely, [{Ce（pdca）（H20）} {Ce（pdca）（H20）5}]2{MosO26}o10H2O （1）, [Cu（phen）（HzO）2]2[Mo6O20] （2） （pdca=pyridine-2,6- dicarboxylic acid, phen= 1,10-phenanthroline） have been successfully synthesized under hydrothermal conditions, and characterized by elemental analyses, IR spectra, thermal gravimetric analyses （TGA）, single-crystal X-ray diffraction and powder X-ray diffraction （PXRD）. In compound 1, Ce（III） ions are bridged by pdca ligands to form ce- rium-organic coordination layers, which are further pillared by octamolybdate clusters via the covalent bonding of Ce--O, leading to the formation of a 3D pillar-layered open-framework architecture. Compound 2 features a 3D supramolecular structure constructed by hydrogen bond interactions between 1D molybdate chains aggregated by [M06020]4- polyoxoanions and coordinated water molecules. It was remarkable that H3[PMol2040]·XH20 decomposes into hexamolybdate anions, which are linked together with phen ligands by Cu（II） cation. Moreover, UV-vis spectra and fluorescence properties of compounds 1- 2 have also been investigated in detail.