Efficient CO2/N2 separation by mixed matrix membrane with amide functionalized porous coordination polymer filler

A new Pebax-based mixed matrix membrane with amide functionalized PCP filler shows promising CO₂/N₂ separation at ambient temperature.     

Breathing Effect via Solvent Inclusions on the Linker Rotational Dynamics of Functionalized MIL-53

The breathing effects of functionalized MIL-53-X (X=H, CH₃, NH₂, OH, and NO₂) induced by the inclusions of water, methanol, acetone, and N,N-dimethylformamide solvents were comprehensively investigated by solid-state NMR spectroscopy. 2D homo-nuclear correlation NMR provided direct experimental evidence for the host-guest interaction between the guest solvents and the MOF frameworks. The variations of the ¹H and ¹³C NMR chemical shifts in functionalized MIL-53 from the narrow pore phase transitions to large pore forms due to solvent inclusions were clearly identified. The influence of functionalized linkers and their host-guest interactions with the confined solvents on the rotational dynamics of the linkers was examined by separated-local-field MAS NMR experiments in conjunction with DFT theoretical calculations. It is found that the linker rotational dynamics of functionalized MIL-53 in narrow pore form is closely related to the computational rotational energy barrier. The BDC-NO₂ linker of activated MIL-53-NO₂ undergoes relatively faster rotation, whereas the BDC-NH₂ and BDC-OH linkers of activated MIL-53-NH₂ and MIL-53-OH exhibit relatively slower rotation. The host-guest interactions between confined solvents and MIL-53-NO₂, MIL-53-CH₃ would significantly induce an increase of the order parameters of unsubstituted carbon and reduce the rotational frequency of linkers. This study provides a spectroscopic approach for the investigation of linker rotation in functionalized MOFs at natural abundance with solvents inclusions.     

Adsorption of CO2 in metal organic frameworks of different metal centres: Grand Canonical Monte Carlo simulations compared to experiments

A Grand Canonical Monte Carlo study has been performed in order to compare the different CO₂ adsorption mechanisms between two members of the MIL-n family of hybrid metal-organic framework materials. The MIL-53 (Al) and MIL-47 (V) systems were considered. The results obtained confirm that there is a structural interchange between a large pore and narrow pore forms of MIL-53 (Al), not seen with the MIL-47 (V) material, which is a consequence of the presence of μ ₂-OH groups. The interactions between the CO₂ molecules and these μ ₂ OH groups mainly govern the adsorption mechanism in this MIL-53 (Al) material. The subsequent breaking of these adsorption geometries after the adsorbate loading increases past the point where no more preferred adsorption sites are available, are proposed as key features of the breathing phenomenon. After this, any new adsorbates introduced into the MIL-53 (Al) large pore structure experience a homogeneous adsorption environment with no preferential adsorption sites in a similar way to what occurs in MIL-47 (V).     

Three Cadmium(II) Coordination Polymers based on Mixed 1,2‐Naphthalenedicarboxylate and Bis(pyridyl) Co‐ligands: Structural Diversities and Photoluminescent Properties

Hydrothermal reactions of Cd(OAc)₂ · 2H₂O with 1,2‐naphthalic anhydride in the absence/presence of different rigid/flexible bis(pyridyl) co‐ligands, produce three distinct coordination polymers, namely [Cd(ndc)]_n ( 1 ), {[Cd₅(ndc)₄(bpp)₂(OH)₂](H₂O)₄}_n ( 2 ), and [Cd₅(ndc)₄(bpy)₂(OH)₂]_n ( 3 ) [ndc = 1,2‐naphthalenedicarboxylate, bpp = 1,3‐bis(4‐pyridyl)propane, and bpy = 4,4′‐bipyridine]. Complex 1 contains dinuclear [Cd₂O₂] clusters as secondary building units (SBUs) and shows a two‐dimensional (2D) kgd network. Complexes 2 and 3 possess one‐dimensional (1D) chains based on pentanuclear [Cd₅(μ₃‐OH)₂(COO)₂] units as SBUs, which are further extended to afford 2D sql sheet via flexible bpp in 2 and three‐dimensional (3D) pcu network via rigid bpy in 3 , respectively. The structural diversities indicate that the bis(pyridyl) co‐ligands with different flexibility play a key role on the formation of the final supramolecular structures. The complexes were characterized by X‐ray crystallographic, IR, elemental, thermal stability, and powder X‐ray diffraction analyses. In addition, the photoluminescent properties in solid state were also investigated.     

Very large breathing effect in the first nanoporous chromium(III)-based solids: MIL-53 or Cr(III)(OH) x [O(2)C-C(6)H(4)-CO(2)] x [HO(2)C-C(6)H(4)-CO(2)H](x) x H(2)O(y)

The first three-dimensional chromium(III) dicarboxylate, MIL-53as or Cr(III)(OH) x [O(2)C-C(6)H(4)-CO(2)].[HO(2)C-C(6)H(4)-CO(2)H](0.75), has been obtained under hydrothermal conditions (as: as-synthesized). The free acid can be removed by calcination giving the resulting solid, MIL-53ht or Cr(III)(OH) x [O(2)C-C(6)H(4)-CO(2)]. At room temperature, MIL-53ht adsorbs atmospheric water immediately to give Cr(III)(OH) x [O(2)C-C(6)H(4)-CO(2)] x H(2)O or MIL-53lt (lt: low-temperature form, ht: high-temperature form). Both structures, which have been determined by using X-ray powder diffraction data, are built up from chains of chromium(III) octahedra linked through terephthalate dianions. This creates a three-dimensional structure with an array of one-dimensional large pore channels filled with free disordered terephthalic molecules (MIL-53as) or water molecules (MIL-53lt); when the free molecules are removed, this leads to a nanoporous solid (MIL-53ht) with a Langmuir surface area over 1500 m(2)/g. The transition between the hydrated form (MIL-53lt) and the anhydrous solid (MIL-53ht) is fully reversible and followed by a very high breathing effect (more than 5 A), the pores being clipped in the presence of water molecules (MIL-53lt) and reopened when the channels are empty (MIL-53ht). The thermal behavior of the two solids has been investigated using TGA and X-ray thermodiffractometry. The sorption properties of MIL-53lt have also been studied using several organic solvents. Finally, magnetism measurements performed on MIL-53as and MIL-53lt revealed that these two phases are antiferromagnetic with Néel temperatures T(N) of 65 and 55 K, respectively. Crystal data for MIL-53as is as follows: orthorhombic space group Pnam with a = 17.340(1) A, b = 12.178(1) A, c = 6.822(1) A, and Z = 4. Crystal data for MIL-53ht is as follows: orthorhombic space group Imcm with a = 16.733(1) A, b = 13.038(1) A, c = 6.812(1) A, and Z = 4. Crystal data for MIL-53lt is as follows: monoclinic space group C2/c with a = 19.685(4) A, b = 7.849(1) A, c = 6.782(1) A, beta = 104.90(1) degrees, and Z = 4.     

金属有机骨架材料MIL-53(Al)负载钴催化剂的CO催化氧化反应性能

采用溶剂法合成了热稳定性高的金属有机骨架材料MIL-53(Al)(MIL:Materials of Institut Lavoisier),用此材料为载体负载钴催化剂用于CO的催化氧化反应,并与Al2O3负载的钴催化剂进行了对比.采用热重-差热扫描量热(TG-DSC)、傅里叶变换红外(FTIR)光谱、X射线衍射(XRD)、N2物理吸附-脱附、透射电子显微镜(TEM)、氢气程序升温还原(H2-TPR)等方法对催化剂的结构性质进行了表征.TG和N2物理吸附-脱附结果表明,载体MIL-53(Al)有好的稳定性和高的比表面积;XRD以及TEM结果表明Co/MIL-53(Al)上负载的Co3O4颗粒粒径(平均约为5.03 nm)明显小于Al2O3上Co3O4颗粒粒径(平均约为7.83 nm).MIL-53(Al)的三维多孔结构中分布均匀的位点能很好地分散固定Co3O4颗粒,高度分散的Co3O4颗粒有利于CO的催化氧化反应.H2-TPR实验发现Co/MIL(Al)催化剂的还原温度低于Co/Al2O3催化剂的还原温度,低的还原温度表现为高的催化氧化活性.CO催化氧化结果表明,MIL-53(Al)负载钴催化剂的催化活性明显高于Al2O3负载钴催化剂,MIL-53(Al)负载钴催化剂在160°C时使CO氧化的转化率达到98%,到180°C时CO则完全转化,催化剂的结构在催化反应过程中保持稳定.     

A rationale for the large breathing of the porous aluminum terephthalate (MIL-53) upon hydration

Aluminum 1,4-benzenedicarboxylate Al(OH)[O(2)C-C(6)H(4)-CO(2)]. [HO(2)C-C(6)H(4)-CO(2)H](0.70) or MIL-53 as (Al) has been hydrothermally synthesized by heating a mixture of aluminum nitrate, 1,4-benzenedicarboxylic acid, and water, for three days at 220 degrees C. Its 3 D framework is built up of infinite trans chains of corner-sharing AlO(4)(OH)(2) octahedra. The chains are interconnected by the 1,4-benzenedicarboxylate groups, creating 1 D rhombic-shaped tunnels. Disordered 1,4-benzenedicarboxylic acid molecules are trapped inside these tunnels. Their evacuation upon heating, between 275 and 420 degrees C, leads to a nanoporous open-framework (MIL-53 ht (Al) or Al(OH)[O(2)C-C(6)H(4)-CO(2)]) with empty pores of diameter 8.5 A. This solid exhibits a Langmuir surface area of 1590(1) m(2)g(-1) together with a remarkable thermal stability, since it starts to decompose only at 500 degrees C. At room temperature, the solid reversibly absorbs water in its tunnels, causing a very large breathing effect and shrinkage of the pores. Analysis of the hydration process by solid-state NMR ((1)H, (13)C, (27)Al) has clearly indicated that the trapped water molecules interact with the carboxylate groups through hydrogen bonds, but do not affect the hydroxyl species bridging the aluminum atoms. The hydrogen bonds between water and the oxygen atoms of the framework are responsible for the contraction of the rhombic channels. The structures of the three forms have been determined by means of powder X-ray diffraction analysis. Crystal data for MIL-53 as (Al) are as follows: orthorhombic system, Pnma (no. 62), a = 17.129(2), b = 6.628(1), c = 12.182(1) A; for MIL-53 ht (Al), orthorhombic system, Imma (no. 74), a = 6.608(1), b = 16.675(3), c = 12.813(2) A; for MIL-53 lt (Al), monoclinic system, Cc (no. 9), a = 19.513(2), b = 7.612(1), c = 6.576(1) A, beta = 104.24(1) degrees.     

苯部分加氢制环己烯新型Ru-B/MOF催化剂

制备了多种金属-有机骨架(MOF)材料,采用浸渍-化学还原法制备了非晶态Ru-B/MOF催化剂,考察了它们在苯部分加氢反应中的催化性能.催化性能评价结果表明,这些催化剂的初始反应速率(r0)顺序为Ru-B/MIL-53(Al)Ru-B/MIL-53(Al)-NH2Ru-B/UIO-66(Zr)Ru-B/UIO-66(Zr)-NH2Ru-B/MIL-53(Cr)Ru-B/MIL-101(Cr)Ru-B/MIL-100(Fe),环己烯初始选择性(S0)顺序为Ru-B/MIL-53(Al)≈Ru-B/MIL-53(Cr)Ru-B/UIO-66(Zr)-NH2Ru-B/MIL-101(Cr)Ru-B/MIL-53(Al)-NH2Ru-B/UIO-66(Zr)≈Ru-B/MIL-100(Fe).催化性能最好的Ru-B/MIL-53(Al)催化剂上的r0和S0分别为23 mmol·min-1·g-1和72%.采用多种手段,对催化性能差异最为显著的Ru-B/MIL-53(Al)和Ru-B/MIL-100(Fe)催化剂的物理化学性质进行了表征.发现MIL-53(Al)载体能够更好地分散Ru-B纳米粒子,粒子的平均尺寸为3.2 nm,而MIL-100(Fe)载体上Ru-B纳米粒子团聚严重,粒径达46.6 nm.更小的粒径不仅能够提供更多的活性位,而且也有利于环己烯选择性的提高.对Ru-B/MIL-53(Al)催化剂的反应条件进行了优化,在180°C和5 MPa的H2压力下,环己烯得率可达24%,展示了MOF材料用作苯部分加氢催化剂载体的良好前景.     

金属有机框架@介孔分子筛复合材料的构建和性质

通过蒸汽诱导内部水解法(VIH)在介孔分子筛SBA-15孔壁上引入Al_2O_3,合成得到Al_2O_3@SBA-15复合物,随后与对二苯甲酸配体反应,从而制备得到金属有机框架化合物(MIL-53)与介孔分子筛(SBA-15)复合材料(MIL-53@SBA-15)。采用粉末X射线衍射(PXRD)、N_2吸附-脱附测试、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等技术证明成功合成了MIL-53@SBA-15复合材料。染料吸附实验结果表明,MIL-53@SBA-15复合材料相比于SBA-15、MIL-53及其物理混合样品,表现出对丁基罗丹明染料更高效吸附特性。     

A Series of Three‐Dimensional Rare Earth Coordination Polymers with Two Binary Carboxylate as Mixed‐Ligand: Syntheses,Structures, Properties of [LnIII(mal)(ox)0.5(H2O)2]·2H2O (Ln = Pr,Nd, and La)

A series of lanthanide coordination polymers, [Ln^III(mal)(ox)_0.5(H₂O)₂]·2H₂O (Ln = Pr ( 1 ), Nd ( 2 ), and La ( 3 ); H₂mal= maleic acid; H₂ox = oxalic acid), were synthesized firstly by the reaction of Ln^III nitrate salts with maleic anhydrid and oxalic acid under hydrothermal conditions and were characterized by elemental analysis, IR spectroscopy, and single‐crystal X‐ray diffraction. X‐ray diffraction analyses reveal that they are crystallized in orthorhombic space group Fddd. Lanthanide metal center atom (Ln) and its corresponding centrosymmtric atom link through two chelating/bridging bidentate carboxyl groups of maleic acid ligands to form an infinite inorganic rod‐shaped building unit. These rod‐shaped building units were linked to each other through the carbon atoms of the maleate anions on the [110] plane to form lanthanide‐maleic acid layers. The oxalic acid pillared lanthanide‐maleic acid layers with intersected channels by free water molecules consist of a 3D framework structure. The thermogravimetric analyses of 1 – 3 were discussed in detail. The courses of the thermal decomposition of complexes are similar.     

Modular,Homochiral, Porous Coordination Polymers: Rational Design,Enantioselective Guest Exchange Sorption and Ab Initio Calculations of Host–Guest Interactions

Two new, homochiral, porous metal–organic coordination polymers [Zn₂(ndc){(R)‐man}(dmf)]?3DMF and [Zn₂(bpdc){(R)‐man}(dmf)]?2DMF (ndc=2,6‐naphthalenedicarboxylate; bpdc=4,4′‐biphenyldicarboxylate; man=mandelate; dmf=N,N′‐dimethylformamide) have been synthesized by heating Zn^II nitrate, H₂ndc or H₂bpdc and chiral (R)‐mandelic acid (H₂man) in DMF. The colorless crystals were obtained and their structures were established by single‐crystal X‐ray diffraction. These isoreticular structures share the same topological features as the previously reported zinc(II) terephthalate lactate [Zn₂(bdc){(S)‐lac}(dmf)]?DMF framework, but have larger pores and opposite absolute configuration of the chiral centers. The enhanced pores size results in differing stereoselective sorption properties: the new metal–organic frameworks effectively and stereoselectively (ee up to 62 %) accommodate bulkier guest molecules (alkyl aryl sulfoxides) than the parent [Zn₂(bdc){(S)‐lac}(dmf)]?DMF, while the latter demonstrates decent enantioselectivity toward precursor of chiral anticancer drug sulforaphane, CH₃SO(CH₂)₄OH. The new homochiral porous metal–organic coordination polymers are capable of catalyzing a highly selective oxidation of bulkier sulfides (2‐NaphSMe (2‐C₁₀H₇SMe) and PhSCH₂Ph) that could not be achieved by the smaller‐pore [Zn₂(bdc){(S)‐lac}(dmf)]?DMF. The sorption of different guest molecules (both R and S isomers) into the chiral pores of [Zn₂(bdc){(S)‐lac}(dmf)]?DMF was modeled by using ab initio calculations that provided a qualitative explanation for the observed sorption enantioselectivity. The high stereo‐preference is accounted for by the presence of coordinated inner‐pore DMF molecule that forms a weak C? H???O bond between the DMF methyl group and the (S)‐PhSOCH₃ sulfinyl group.     

Three Silver(I) Coordination Polymers Constructed from Flexible Bis(benzimidazole) and Carboxylates Ligands

Under hydrothermal conditions, three new Ag^I coordination polymers, [Ag(L1)(Hmip)]_n ( 1 ), [Ag(L2)_0.5(ndc)_0.5]_n ( 2 ), and {[Ag(L3)_0.5(Htbi)] · 0.25H₂O}_n ( 3 ) [H₂mip = 5‐methylisophthalic acid, L1 = 1,4‐bis(2‐methylbenzimidazol‐1‐ylmethyl)benzene, H₂ndc = 2,6‐naphthalenedicarboxylic acid, L2 = 1,3‐bis(2‐methylbenzimidazol‐1‐ylmethyl)benzene, H₂tbi = 5‐tert‐butyl isophthalic acid, L3 = 1,4‐bis(5,6‐dimethylbenzimidazole)butane] were synthesized by employing flexible bis(benzimidazole) and dicarboxylic acid ligands. Polymer 1 displays a 2D 4‐connected 4L2 underlying net topology with the point symbol of (6⁵.8) in standard representation. Compound 2 possesses a 2D uninodal 4‐connected Shubnikov tetragonal plane net (sql) based on a dinuclear Ag^I clusters with the point symbol (4⁴.6²), which is further extended into a 3D supramolecular framework by π–π interactions. Compound 3 possesses dinuclear molecular complex groups, which form chains by weak Ag–O (2.6 Å) coordination bonds, and further assembled into a 2D supramolecular layer by hydrogen bonds and π–π stacking interactions. These complexes exhibit intense fluorescent emissions in solid state. UV/Vis diffuse reflection spectra and the excellent catalytic activity for the degradation of the congo red azo dye in a Fenton‐like process are discussed.     

Estimation of the desorption energy of dichloromethane and water in MIL-53 by DSC and ab-initio calculations

Desorption energies of dichloromethane(CH_2Cl_2) and water(H_2O) in a metal-organic framework, MIL-53(Al), were investigated by the combination of experimental(differential scanning calorimeter, DSC) and computational(ab-initio calculations) methods. The differences of desorption energy and natural log of the frequency factor of CH_2Cl_2 and H_2O in MIL-53(Al) were analyzed by a thermo active process using DSC measurements. The interaction energy of guest molecules with MIL-53(Al), which corresponds to the desorption in the thermal active process, was explored using ab-initio calculation. As a result of the difference in the interaction energies of H_2O and CH_2Cl_2 in MIL-53(Al), the site near the μ_2-OH groups has two potential wells. Both experimentally and computationally, MIL-53 presents the preferential adsorption of CH_2Cl_2 than H_2O.     

Thermodynamics of adsorption of aromatic compounds from non-aqueous solutions by MIL-53(Al) metal-organic framework

The thermodynamics of adsorption of mono-, di-, and tricyclic aromatic compounds by MIL-53(Al) metal-organic framework from their solutions in MeCN, MeOH and n-C₆H₁₄–PrⁱOH was studied for the first time. It was found that the adsorption of the test substances from solutions in MeCN and MeOH is characterized by positive values of enthalpy and entropy changes, and the adsorption from n-C₆H₁₄–PrⁱOH medium is characterized by negative enthalpy and entropy changes. Upon adsorption by MIL-53(Al) framework from polar media, aromatic compounds were proposed to transfer from the liquid phase with a higher degree of association into the solvent medium with a lower degree of association, molecules of which are disordered due to the strong interaction with the hydrophobic walls of the framework pores. It was concluded that the driving force of adsorption by MIL-53(Al) from MeCN and MeOH is increase in entropy of the system, while the factor of adsorption from n-C₆H₁₄–PrⁱOH medium is decrease in enthalpy of the adsorption system. The compensation effect in liquid-phase adsorption of aromatic compounds by MIL-53(Al) framework was discovered. The effect of the liquid phase nature on selectivity of adsorption from solutions onto investigated metal-organic framework was demonstrated.     

Metal-Dependent and Selective Crystallization of CAU-10 and MIL-53 Frameworks through Linker Nitration

The reaction of the V-shaped linker molecule 5-hydroxyisophthalic acid (H₂L⁰), with Al or Ga nitrate under almost identical reaction conditions leads to the nitration of the linker and subsequent formation of metal–organic frameworks (MOFs) with CAU-10 or MIL-53 type structure of composition [Al(OH)(L)], denoted as Al-CAU-10-L^{0, 2, 4, 6} or [Ga(OH)(L)], denoted as Ga-MIL-53-L². The Al-MOF contains the original linker L⁰ as well as three different nitration products (L², L⁴ and L^4/6), whereas the Ga-MOF mainly incorporates the linker L². The compositions were deduced by ¹H NMR spectroscopy and confirmed by Rietveld refinement. In situ and ex situ studies were carried out to follow the nitration and crystallization, as well as the composition of the MOFs. The crystal structures were refined against powder X-ray diffraction (PXRD) data. As anticipated, the use of the V-shaped linker results in the formation of the CAU-10 type structure in the Al-MOF. Unexpectedly, the Ga-MOF crystallizes in a MIL-53 type structure, which is usually observed with linear or slightly bent linker molecules. To study the structure directing effect of the in situ nitrated linker, pure 2-nitrobenzene-1,3-dicarboxylic acid (m-H₂BDC-NO₂) was employed which exclusively led to the formation of [Ga(OH)(C₈H₃NO₆)] (Ga-MIL-53-m-BDC-NO₂), which is isoreticular to Ga-MIL-53-L². Density Functional Theory (DFT) calculations confirmed the higher stability of Ga-MIL-53-L² compared to Ga-CAU-10-L² and grand canonical Monte Carlo simulations (GCMC) are in agreement with the observed water adsorption isotherms of Ga-MIL-53-L².     

Influence of Flexible Bis(benzimidazole) Derivatives on the Self‐assembly of Three Mixed Ligands Silver(I) Coordination Polymers

Three silver(I) coordination polymers namely, [Ag₄(L1)₂(1, 4‐ndc)₂]_n ( 1 ) {[Ag(L2)] · (1, 4‐Hndc) · H₂O}_n ( 2 ), and {[Ag(L3)(H₂O)] · (1, 4‐Hndc)}_n ( 3 ) [L1 = 1, 3‐bis(benzimidazol‐1‐ylmethyl)benzene, 1, 4‐H₂ndc = 1, 4‐naphthalenedicarboxylic acid, L2 = 1, 3‐bis(5, 6‐dimethylbenzimidazole‐1‐ylmethyl)benzene, L3 = 1, 4‐bis(5, 6‐dimethylbenzimidazole)butane], were hydrothermally synthesized and characterized by single‐crystal X‐ray diffraction analysis, elemental analysis, IR spectroscopy, thermogravimetric and XRPD analysis. Complex 1 displays a 1D tube‐like chain, which is packed into a 3D supramolecular network by π–π stacking interactions. Complex 2 features an infinite 1D linear chain. Complex 3 contains a 1D wave‐like chain, which is extended into a 3D supramolecular network through O–H ··· O hydrogen bonding interactions. Moreover, these coordination polymers exhibit catalytic properties for degradation of methyl orange in Fenton‐like processes.     

A Low-Temperature Approach for the Phase-Pure Synthesis of MIL-140 Structured Metal–Organic Frameworks

In a systematic investigation, the synthesis of metal–organic frameworks (MOFs) with MIL-140 structure was studied. The precursors of this family of MOFs are the same as for the formation of the well-known UiO-type MOFs although the synthesis temperature for MIL-140 is significantly higher. This study is focused on the formation of Zr-based MIL-140 MOFs with terephthalic acid (H₂bdc), biphenyl-4,4′-dicarboxylic acid (H₂bpdc), and 4,4′-stilbenedicarboxylic acid (H₂sdc) and the introduction of synthesis field diagrams to discover parameters for phase-pure products. In this context, a MIL-140 network with H₂sdc as linker molecule is first reported. Additionally, an important aspect is the reduction of the synthesis temperature to make MIL-140 MOFs more accessible even though linkers with a more delicate nature are used. The solvothermal syntheses were conducted in highly concentrated reaction mixtures whereby a targeted synthesis to yield the MIL-140 phase is possible. Furthermore, the effect of the often-used modulator approach is examined for these systems. Finally, the characteristics of the synthesized MOFs are compared with physisorption measurements, thermogravimetric analyses, and scanning electron microscopy.     

Copper-doped sulfonic acid-functionalized MIL-101(Cr) metal–organic framework for efficient aerobic oxidation reactions

A series of Cr-based metal–organic framework MIL-101-SO₃H bearing sulfonic acid functional groups were utilized for the immobilization of catalytically active copper species via a post-synthetic metalation method. The novel materials were fully characterized by scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), the Brunauer–Emmett–Teller method, and thermogravimetric analysis. XPS and the EDX element map both suggested that Cu²⁺ is coordinately bonded to the MIL-101-SO₃H, which forms the MIL-101-SO₃@Cu structure. The obtained copper-doped MIL-101-SO₃@Cu-1, MIL-101-SO₃@Cu-2, and MIL-101-SO₃@Cu-3 catalysts were utilized in the selective oxidation of alcohols and epoxidation of olefins using molecular oxygen as an oxidant. Catalytic aerobic oxidation optimization showed that MIL-101-SO₃@Cu-1 is the optimal catalyst and it can be reused ten times without compromising the yield and selectivity.     

Hydrothermal synthesis and crystal structure of a new 2D metal-organic framework: [Gd(Oba)(Ox)0.5(H2O)2]n (H2Oba = 4,4′-oxybis(benzoic acid); H2Ox = oxalic acid)

A new coordination polymer [Gd(Oba)(Ox)_0.5(H₂O)₂] _n (I) (H₂Oba = 4,4′-oxybis(benzoic acid), H₂Ox = oxalic acid) has been synthesized by hydrothermal reactions and characterized by elemental analysis and single-crystal X-ray diffraction. In I, two Gd³⁺ ions are bridged by Oba ligands to form 1D ribbon chains, which are further connected by Ox ligands, generating a 2D layer structure.     

Incorporation of metallocenes into the channel structured Metal-Organic Frameworks MIL-53(Al) and MIL-47(V)

A selection of metallocene inclusion compounds with channel structured MOFs (MOF = Metal-Organic Framework) were obtained via solvent-fee adsorption of the metallocenes from the gas-phase. The adsorbate structures ferrocene(0.5)@MIL-53(Al) (MIL-53(Al) = [Al(OH)(bdc)](n) with bdc = 1,4-terephthalate), ferrocene(0.25)@MIL-47(V) (MIL-47(V) = [V(O)(bdc)](n)), cobaltocene(0.25)@MIL-53(Al), cobaltocene(0.5)@MIL-47(V), 1-formylferrocene(0.33)@MIL-53(Al), 1,1'dimethylferrocene(0.33)@MIL-53(Al), 1,1'-diformylferrocene(0.5)@MIL-53(Al) were determined from powder X-ray diffraction data and were analyzed concerning the packing and orientation of the guest species. The packing of the ferrocene guest molecules inside MIL-47(V) is significantly different compared to MIL-53(Al) due to the lower breathing effect and weaker hydrogen bonds between the guest molecules and the host network in the case of MIL-47(V). The orientation of the metallocene molecule is also influenced by the substituents (CH(3) and CHO) at the cyclopentadienyl ring and the interaction with the bridging OH group of MIL-53(Al). The inclusion of redox active cobaltocene into MIL-47(V) leads to the formation of a charge transfer compound with a negatively charged framework. The reduction of the vanadium centers is stoichiometric. The resulting material is a mixed valence compound with a V(3+)/V(4+) ratio of 1:1. The new compounds were characterized via thermal gravimetric analysis, infrared spectroscopy, solid state NMR, and differential pulse voltammetry. Both systems are 1D-channel pore structures. The metallocene adsorbate induced breathing effect of MIL-53(Al) is more pronounced compared to MIL-47(V), this can be explained by the different bridging groups between the MO(6) clusters.