Three-component reactions leading to 2D and 3D metal-organic frameworks assembled on dinickel-carboxylate secondary building units

Three-component reactions involving Ni(II) ions and dicarboxylate and bipyridyl ligands under hydrothermal conditions produce two novel metal-organic coordination polymers formulated empirically as [Ni(PDA)(BPE)] (1) and [Ni₂(PDA)₂(BPP)(H₂O)]·2.5H₂O (2), where PDA = 1,4-phenylenediacetate, BPE = 1,2-bis(4-pyridyl)ethane, and BPP = 1,3-bis(4-pyridyl)propane. Both compounds possess 2D or 3D metal-organic frameworks (MOFs) that are assembled on dinickel-carboxylate secondary building units. Compound 1 has a condensed 3D MOF, whereas 2 contains void between 2D MOFs where guest water molecules reside. Both compounds demonstrate antiferromagnetic coupling between Ni(II) ions.     

Influence of temperature on metal-organic frameworks

Reaction temperature is one of the key parameters in the synthesis of metal-organic frameworks （MOFs）. Though there is no convergence with regard to the various experimental parameters, reaction temperature has been found to have remarkable influence on the formation and structure of MOFs, especially toward the control of topology and dimensionality of the MOF structures. Theoretically, the reaction temperature affects directly the reaction energy barrier in reaction thermodynamics and the reaction rate in the reaction kinetics. This review aims to show the influence of reaction temperature on crystal growth/assembly, structural modulation and transformation of MOFs, and to provide primary information and insights into the design and assernblv of desired MOFs.     

Construction of mixed carboxylate and pyrogallate building units for luminescent metal-organic frameworks

A metal-organic framework,Ce-FDM-50,was constructed by employing gallic acid featuring both carboxylate and pyrogallate as the coordinating sites and Ce(Ⅲ).The co-assembly of the carboxylates and pyrogallates with two metal ions have achieved a new type of paddle wheel secondary building unit.These building units were further joined by organic struts to obtain frameworks in sql topology.This synthetic approach could be expanded to five different lanthanide metals(Nd,Eu,Gd,Tb,Yb)for the construction of a series of isoreticular MOFs based on FDM-50,and even MTV-MOFs in which mixed lanthanide metals with specific ratios were distributed.In addition,featuring the lanthanide metals as the inorganic nodes in the network,Tb-FDM-50 showed distinct luminescence properties that could be furtherly tuned for variable applications.     

将铂(Ⅱ)-四(4-羧基苯基)卟啉组装到光捕获金属有机框架中增强可见光驱动的产氢效能

氢气析出反应的分子催化剂因能够将其整合到用于光催化水分解的光捕集复合物中而受到广泛关注.研究者期望通过构建吸光网络,提高分子催化剂的光催化产氢效能.本文报道了以[(TCPP)PtⅡ][TCPP=meso-四(4-羧基苯基)卟啉]络合物作为光催化产氢的分子催化剂.采用氯冉酸(CA)作为电子牺牲剂可以很好地稳定光催化剂,使...     

The application of metal-organic frameworks in electrocatalytic nitrogen reduction

In recent years,the research of nitrogen reduction reaction(NRR) under ambient conditions has attracted wide attention for their relatively low energy consumption,in which rational design of electrocatalysts is the key to achieve high-performance NRR.Metal-organic frameworks(MOFs),as a new kind of porous material,have been intensively studied in the past few decades owing to not only their structural versatility and tunability but also intrinsic porosity.Due to their structural features,MOFs als...     

Multi-functional sites catalysts based on post-synthetic modification of metal-organic frameworks

Multi-functional sites MOFs have been explored as a new type of heterogeneous catalytic materials, which can be constructed by various post-synthetic modifications.     

Syntheses,structures and properties of four metal-organic frameworks from chlorophenyl imidazole dicarboxylates

Four metal-organic frameworks, [Sr(o-ClPhHIDC)(H₂O)₂]_n (o-ClPhH₃IDC = 2-(o-chlorophenyl)-1H-imidazole-4,5-dicarboxylic acid) (1), [Mg(m-ClPhHIDC)(H₂O)₂]_n (2), [Sr(m-ClPhHIDC)(H₂O)]_n (3) and {[Co₃(m-ClPhIDC)₂(H₂O)₆]·2H₂O}_n (m-ClPhH₃IDC = 2-(m-chlorophenyl)-1H-imidazole-4,5-dicarboxylic acid) (4), have been solvothermally synthesized and structurally characterized. Single-crystal X-ray analyses reveal that 1–3 show 2-D architectures and 4 exhibits a 3-D structure. The o-ClPhH₃IDC and m-ClPhH₃IDC ligands in the polymers can be partly deprotonated and coordinate to metal ions by various modes. The metal ions of 1–4 are coordinated only to oxygens. The thermal and luminescence properties of the polymers have also been investigated.     

The synthesis of polyoxometalate-based metal-organic frameworks under ionothermal conditions

Using ionic liquid (IL) [Bmim]Br (Bmim=1-butyl-3-methylimidazolium) as solvent has resulted in a polyoxometalate-based metal-organic framework (PMOFs), [Cu^IBbi]₄SiW₁₂O₄₀·H₂O (1) [Bbi=1,1-(1,4-butanediyl)-bis(imidazole)], and was produced via an ionothermal route. Its structure was determined by single-crystal X-ray diffraction. Compound 1 is a 1-D ladder with large voids, resulting in a 3-D supermolecular structure using the classic Keggin-type anion as a second building block. This means utilizing ILs to construct 3-D PMOFs can be efficiently realized. Additionally, electrochemical, electrocatalytic, and photocatalytic properties of 1 were studied.     

Preparation,structure and photocatalysis of metal-organic frameworks derived from aromatic carboxylate and imidazole-based ligands

Three 3-D metal-organic frameworks (MOFs), [Cd(NDC)(biim-4)]·0.5H₂O (1), [Cd₂(TDC)₂(biim-4)₂(H₂O)₂] (2) and [Zn₂(biim-4)₂(TDC)₂]·2.5H₂O (3) (biim-4 = 1,4-bis(1-imidazolyl) butyric alkyl; H₂NDC = 1,4-naphthalene dicarboxylic acid; H₂TDC = thiophene-2,5-dicarboxylic acid), have been synthesized under hydrothermal conditions and structurally characterized by single X-ray diffraction. The three MOFs have high photocatalytic degradation effects on methyl orange under UV irradiation. Through electronic structure analysis combined with time-dependent density functional theory calculations, catalytic performances of these materials are correlated with the molecular composition and the optoelectronic properties of the samples.     

Two new metal-organic frameworks possessing binodal high-connected topologies based on Cd4-clusters and organic ligands

Two new compounds, [Cd₂(bptc)(bpimb)(H₂O)]?·?2H₂O (1) and [Cd₂(bptc)(bpib)]?·?4H₂O (2) (where H₄bptc?=?biphenyl-3,3′,4,4′-tetracarboxylic acid, bpimb?=?1,3-bis((2-(pyridin-2-yl)-1H-imidazol-1-yl)methyl)benzene, bpib?=?1,4-bis(2-(pyridin-2-yl)-1H-imidazol-1-yl)butane), were synthesized by reactions of the corresponding metal salts with H₄bptc and N-containing auxiliary ligands and their structures have been determined by single-crystal X-ray diffraction. Compound 1 is built by Cd₄-clusters which further construct a 3-D (3,8)-connected framework with tfz-d notation; 2, also built by Cd₄-clusters, is a 3-D (4,8)-connected framework with (3²?·?4²?·?5²)(3⁴?·?4⁸?·?5¹²?·?6⁴) topology. In addition, the elemental analyses, infrared spectra, fluorescence, and thermogravimetric analyses for 1 and 2 are discussed.     

Conformational analysis of 1,2-dichloroethane adsorbed in metal-organic frameworks

This paper describes the conformational analysis of 1,2-dichloroethane adsorbed into three different metal-organic frameworks, MIL-53(Al), MIL-68(In), MIL-53-NH₂(Al), by using FT-Raman spectroscopy in combination with powder XRD and TGA. For non-polar frameworks, the main guest-host interactions are van der Waal interactions between the CH bonds of 1,2-dichloroethane (DCE) and the π system of terephthalate ligands. The polar framework of MIL-53-NH₂ is able to stabilize the gauche conformation of DCE at room temperature. The conformational enthalpy of each system was determined through variable temperature FT-Raman spectroscopy. Furthermore, the line-width of the Raman bands provides information regarding the molecular motion of the halocarbons at various temperatures inside the framework.     

Tuning the release rate of volatile molecules by pore surface engineering in metal-organic frameworks

Encapsulation and controlled release of volatile molecules such as fragrances in a designed manner is important but challenging for the flavor and fragrance industry. Here, we report the tuning release of volatile molecules by postsynthetic modification of an amine-terminated metal-organic framework(MOF) MIL-101-NH_2. By amidation, we obtained three MIL-101 MOFs, the trimethylacetamideterminated TC-MIL-101, the benzamide-terminated BC-MIL-101, and the oxalic acid monoamideterminated OC-MIL-101. All the MOFs can efficiently encapsulate volatile molecules. Moreover, we demonstrate that the release profile of volatiles can be widely tuned to sustain the release in several days to months and even over a year using different modified MIL-101 MOFs. We show that the release profiles are correlated with the binding energies between the guest volatiles and pores in MOFs. The pore diffusion and the synergistic transport are the rate-limiting step of the guest molecules from the modified MOFs.     

Rational design and syntheses of 0-D, 1-D, and 2-D metal-organic frameworks (MOFs) from ferrocenedicarboxylate tetrametallic macrocyclic building units and subsidiary ligands

We have designed and synthesized three new metal-1,1′-ferrocenedicarboxylate complexes containing tetrametallic macrocyclic building units, namely, [Cd₂(η²-O₂CFcCO₂-η²)₂(phen)₂(H₂O)₂] · 4CH₃OH (1) (Fc = (η⁵-C₅H₄)Fe(C₅H₄-η⁵), phen = 1,10-phenanthroline), {[Cd(η²-O₂CFcCO₂)(pebbm)(H₂O)] · 2H₂O}_n (2) (pebbm = 1,1′-(1,5-pentanediyl)bis-1H-benzimidazole) and {[Cd(η²-O₂CFcCO₂-η²)(prbbm)(H₂O)] · 3H₂O}_n (3) (prbbm = 1,1′-(1,3-propanediyl)bis-1H-benzimidazole). Compound 1 is a 0-D discrete tetrametallic macrocyclic framework. Compound 2 features an infinite 1-D ribbon of rings structure constructed by the subsidiary ligands pebbm connecting tetrametallic macrocyclic building units. For 3, its tetrametallic macrocyclic building units are linked by the subsidiary ligands prbbm to form a 2-D network structure. The structural features of these complexes indicate that the ferrocenedicarboxylate tetrametallic macrocycle can be used as a successful molecular building unit and the shapes and conformational flexibility of subsidiary ligands play a crucial role in the manipulation of the configuration of the resultant MOFs. Their fluorescence spectra in solid state at room temperature suggest that the fluorescence emissions of 1-3 are ruled by 1,1′-ferrocenedicarboxylate ligand.     

Construction of metal-organic frameworks through coordination and hydrogen bonding interactions: Syntheses, structures and photoluminescent properties of metal complexes with macrocyclic ligand

A macrocyclic ligand L with two diethylenetriamine units linked by two rigid biphenylene spacers was used as building block for construction of metal-organic frameworks. A silver(I) complex with macrocyclic and open-chain mix-type ligands [Ag₂(L)(L′)](ClO₄)₂ (1) [L′=1,6-bis(4-imidazol-1′-ylmethylphenyl)-2,5-diazahexane] was obtained by reaction of L and L′ together with AgClO₄·H₂O. It is interesting that the open-chain tetradentate ligand L′ only served as a bidentate ligand to bridge the Ag₂L units into an infinite one-dimensional (1D) cationic chain. Neutral 1D chain coordination polymer [Cu₂(L)(μ-SO₄)₂]·3H₂O·3MeOH (2) is formed by sulfate bridges between the neighboring Cu₂L units. When L reacted with nickel(II) sulfate instead of copper(II) sulfate, a monomacrocycle molecular complex [Ni₂(L)(H₂O)₄(SO₄)₂] (3) was obtained in which the sulfate anion acts as monodentate ligands rather than as bridges. When Cd(II) salts were used for the reactions with L, another two neutral 1D coordination polymers, [Cd₂(L)(μ-Cl)₂Cl₂]·2H₂O (4) and [Cd₂(L)(μ-Br)₂Br₂] (5), with the same structure were isolated. All the synthesized complexes exhibit three-dimensional framework structures linked by various hydrogen bonds. The photoluminescent properties of the synthesized complexes were studied in the solid state at room temperature, and the Ag(I) and Cd(II) complexes were found to show strong blue luminescence.     

Size-controlled flow synthesis of metal-organic frameworks crystals monitored by in-situ ultraviolet-visible absorption spectroscopy

Size-controlled flow synthesis of nanoporous particles are of considerable interest for future industrial applications,however,is facing challenges due to lack of in-situ method for size-characterization in fluidic environment.We present that ultraviolet-visible(UV-vis) absorption spectroscopy can be integrated into a flow-synthesis system which was produced by femtosecond laser micro machining.The shift of the absorption peak position of the ex-situ and in-situ UV-vis spectra correlates to variation of size of porous metal-organic frameworks crystals.ZIF-67 crystals with a size in the range from 200 nm to1025 nm are fabricated with the assistance of tri-ethylamine under monitoring of in-situ UV-vis spectra.The ZIF-67 crystals are converted into nanoporous carbons particles with controlled sizes.These materials show size-dependent performance in Na-ion battery and size-independent performance in metal/H_2 O seawater battery.     

Target-induced mimic enzyme deactivation based on mixed-node metal-organic frameworks for colorimetric assay of hydrogen sulfide

Accurate detection of hydrogen sulfide (H₂S) is of great significance for environmental monitoring and protection. We propose a colorimetric method for the detection of H₂S by the use of mixed-node Cu-Fe metal organic frameworks (Cu-Fe MOFs) as highly efficient mimic enzymes for target-induced deactivation. The Cu-Fe MOFs were synthesized by a simple solvothermal method and could catalyze the H₂O₂ mediated oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to oxTMB with a blue color. The presence of dissolved H₂S would deactivate the mimic enzymes, and then the blue color disappeared. The mechanism of the sensor was discussed by steady-state kinetic analysis. The designed assay was highly sensitive for H₂S detection with a linear range of 0−80 μmol/L and a detection limit of 1.6 μmol/L. Moreover, some potential substances in the water samples had no interference. This method with the advantages of low cost, high sensitivity, selectivity, and visual readout with the naked eye was successfully applied to the determination of H₂S in industrial wastewater samples.     

Two-dimensional cobalt metal-organic frameworks for efficient C3H6/CH4 and C3H8/CH4 hydrocarbon separation

A Co-based two-dimensional (2D) microporous metal-organic frameworks (UPC-32) with narrow distance between layers and layers (3.8 Å) exhibits high selectivity of C₃H₆/CH₄ (31.46) and C₃H₈/CH₄ (28.04) at 298 K and 1 bar. It is the first 2D Co-MOF that showed selective separation of C3 hydrocarbon from CH₄.