Rod-shaped Secondary Building Units Research Articles

Highly Emissive and Robust Cd-Based MOF with an Unprecedented Topology for Tetracycline Sensing.

Herein, an unprecedented cadmium-based metal-organic framework (JNU-106) fabricated by utilizing pyrazole-functionalized tetraphenylethylene ligands (Py-TPE) and rod-shaped secondary building units is reported, possessing a new (3,3,3,6,6,8)-connected topological network. Thanks to the ingeniously designed intramolecular charge transfer behavior, which originates from the congruent coplanarity between Py and TPE, JNU-106 exhibits intense green luminescence with a quantum yield increased by 1.5 times. The phenomenon of remarkable fluorescence quenching of JNU-106 reveals that it possesses extremely high anti-interference performance, superior sensitivity, and dedicated selectivity toward tetracycline antibiotics (TCAs) in aqueous solutions, which are comparable to those of the state-of-the-art porous sensing compounds. Taking the theoretical calculations and experimental results into account, the luminescence quenching is mainly attributed to the internal filtration effect and the static quenching effect. Considering the portable and rapid performance of JNU-106-based testing strips for sensing TCAs, the fabricated JNU-106 provides an alternative for ecological monitoring and environmental governance.

Rational Design and Reticulation of Infinite qbe Rod Secondary Building Units into Metal-Organic Frameworks through a Global Desymmetrization Approach for Inverse C3 H8 /C3 H6 Separation.

The development of reticular chemistry has enabled the construction of a large array of metal-organic frameworks (MOFs) with diverse net topologies and functions. However, dominating this class of materials are those built from discrete/finite secondary building units (SBUs), yet the designed synthesis of frameworks involving infinite rod-shaped SBUs remain underdeveloped. Here, by virtue of a global linker desymmetrization approach, we successfully targeted a novel Cu-MOF (Cu-ASY) incorporating infinite Cu-carboxylate rod SBUs with its structure determined by micro electron diffraction (MicroED) crystallography. Interestingly, the rod SBU can be simplified as a unique cylindric sphere packing qbe tubule made of [43 .62 ] tiles, which further connect the tritopic linkers to give a newly discovered 3,5-connected gfc net. Cu-ASY is a permanent ultramicroporous material featuring 1D channels with highly inert surfaces and shows a preferential adsorption of propane (C3 H8 ) over propene (C3 H6 ). The efficiency of C3 H8 selective Cu-ASY is validated by multicycle breakthrough experiments, giving C3 H6 productivity of 2.2 L/kg. Density functional theory (DFT) calculations reveal that C3 H8 molecules form multiple C-H⋅⋅⋅π and atypical C-H⋅⋅⋅ H-C van der Waals interactions with the inner nonpolar surfaces. This work therefore highlights the linker desymmetrization as an encouraging and intriguing strategy for achieving unique MOF structures and properties.

Heterometallic Molecular Complexes Act as Messenger Building Units to Encode Desired Metal-Atom Combinations to Multivariate Metal-Organic Frameworks.

A novel synthetic approach is described for the targeted preparation of multivariate metal–organic frameworks (MTV-MOFs) with specific combinations of metal elements. This methodology is based on the use of molecular complexes that already comprise desired metal-atom combinations, as building units for the MTV-MOF synthesis. These units are transformed into the MOF structural constituents through a ligand/linker exchange process that involves structural modifications while preserving their originally encoded atomic combination. Thus, through the use of heterometallic ring-shaped molecules combining gallium and nickel or cobalt, we have obtained MOFs with identical combinations of the metal elements, now incorporated in the rod-shaped secondary building unit, as confirmed with a combination of X-ray and electron diffraction, electron microscopy, and X-ray absorption spectroscopy techniques.

An indium-based microporous metal–organic framework with unique three-way rod-shaped secondary building units for efficient methane and hydrogen storage

An indium-based microporous metal–organic framework, UTSA-22, with unique three-way rod-shaped secondary building units, exhibits efficient methane and hydrogen storage at room temperature.

Unusual Metal-Organic Framework Topology and Radiation Resistance through Neptunyl Coordination Chemistry.

A Np(V) neptunyl metal-organic framework (MOF) with rod-shaped secondary building units was synthesized, characterized, and irradiated with γ rays. Single-crystal X-ray diffraction data revealed an anionic framework containing infinite helical chains of actinyl-actinyl interaction (AAI)-connected neptunyl ions linked together through tetratopic tetrahedral organic ligands (NSM). NSM exhibits an unprecedented net, demonstrating that AAIs may be exploited to give new MOFs and new topologies. To probe its radiation stability, we undertook the first irradiation study of a transuranic MOF and its organic linker building block using high doses of γ rays. Diffraction and spectroscopic data demonstrated that the radiation resistance of NSM is greater than that of its linker building block alone. Approximately 6 MGy of irradiation begins to induce notable changes in the long- and short-range order of the framework, whereas 3 MGy of irradiation induces total X-ray amorphization and changes in the local vibrational bands of the linker building block.

Synthesis, structure and properties of a novel Cu(II)-MOF {[Cu2L(OH)]·DMF}n based on a semi-rigid polycarboxylic acid ligand

Metal-organic frameworks (MOFs) are coordination polymers with potential voids constructed by organic ligands and metal ions. In this work, we employed a semi-rigid polycarboxylic acid ligand 5-(4-carboxyphenoxy)methyl)benzene-1-thio-3-dicarboxylic acid (H3L) with the flexible “–CH2-O-” group between the two phenyl groups to construct a new Cu(II)-MOF {[Cu2L(OH)]·DMF}n (1). The structure analysis reveals that the adjacent Cu(II) cations are bridged by oxygens from OH– anion and carboxy group to get a one dimensional infinite rod-shaped secondary building unit (SBU). Furthermore, compound 1 exhibits an intriguing three-dimensional MOF based on infinite rod-shaped SBUs and L3-. PXRD result shows compound 1 is still stable after placed in air for three months. The variable-temperature magnetic studies indicate antiferromagnetic behaviors of 1.

High Adsorption Capacity and Selectivity of SO2 over CO2 in a Metal-Organic Framework.

Herein, we report a new metal-organic framework (MOF), namely, ECUT-77, which is built on rod-shaped secondary building units, showing a high Brunauer-Emmett-Teller surface area of 760.3 cm2/g, a pore volume of 0.4 cm3/g, and an aperture of about 1 nm. This MOF enables both high SO2 adsorption capacity up to 8.0 mmol/g at 0.92 bar and room temperature and a high SO2/CO2 selectivity of 44, resulting in excellent SO2 separation upon a ECUT-77 column from a SO2/CO2 mixture containing 2000 ppm of SO2.

Alkaline earth-organic frameworks with amino derivatives of 2,6-naphthalene dicarboxylates: structural studies and fluorescence properties.

Alkaline earth metal ion organic frameworks (AEMOFs) represent a relatively underexplored subcategory of metal-organic frameworks (MOFs). In this contribution, we present the synthesis and structural study of the new MOFs 1-8 based on the alkaline earth ions Mg2+, Ca2+, Sr2+ and Ba2+ and the amino substituted bridging ligands 4-aminonaphthalene-2,6-dicarboxylate (ANDC2-) and 4,8-diaminonaphthalene-2,6-dicarboxylate (DANDC2-). Compounds 1, 5, 6, 7 and 8 constitute rare examples of three-dimensional MOFs which feature square planar M4 secondary building units (SBUs) surrounded by eight bridging ditopic ligands. The underlying topology of MOFs 1, 5, 7 and 8 conforms to the 4-c pcb net which can be simplified to the 8-c bcu net, while 6 adopts the 4-c lta net which simplifies to the 8-c reo net. To the best of our knowledge these are the first examples of MOFs of their structural types formed by linear dicarboxylates instead of trigonal tricarboxylates or tetrahedral tetracarboxylates. Compounds 2, 3 and 4 also feature three dimensional networks with linear rod-shaped SBUs with the Ba2+ MOF 3 displaying an sra rod-net and MOFs 2 and 4 showing very complex rod-nets with so far unique topologies. Fluorescence studies revealed that the free ligands exhibit strong blue-green emission displaying considerable positive solvatochromism thereby pointing towards charge transfer excited states involving the shift of electron density from the amino groups to the aromatic core. Correspondingly, the MOFs display ligand based fluorescence with small differences in emission maxima possibly attributable to the difference in the charge density of the metal ions combined with the different environments around ligands in the crystal structures.

Design of robust rod-packing [In(OH)(BDC)] frameworks and their high CO2/C2-hydrocarbons over CH4 separation performance

The CO2/C2-hydrocarbons over CH4 separation processes are important for the purification of methane fuel. Towards to this purpose, we have designed two isostructural indium-terephthalate metal-organic frameworks (MOFs) decorated with inorganic OH− anions and/or organic –OH Lewis basic groups, namely SNNU-120 and -121. One-dimensional (1D) [In(OH)(COO)2] chains act as rod-shaped secondary building units (SBUs) linking adjacent four SBUs to form robust 3D rod-packing architecture with two types of 1D channels. Under 273 and 298 K, SNNU-120 and -121 have remarkable CO2, C2H2 and C2H4 uptakes but negligible CH4 adsorption. IAST calculations indicate both of them can effectively separate CO2/C2-hydrocarbons from CH4. The gas adsorption and separation performance of inorganic OH− and organic –OH group co-functionalized SNNU-121 MOF are superior to SNNU-120 only with inorganic OH− anions. Specially, the excellent IAST CO2/CH4 (214.4) and C2H4/CH4 (200) selectivity values for SNNU-121 are considered top-level among all rod-packing MOFs and also surpass the values of most famous MOF materials up to now.

Microporous Cobalt(II)-Organic Framework with Open O-Donor Sites for Effective C2H2 Storage and C2H2/CO2 Separation at Room Temperature.

The self-assembly of a bifunctional organic ligand with a formate-bridged rod-shaped secondary building unit leads to a new microporous metal-organic framework (MOF). This MOF shows a moderately high C2H2 storage capacity (145 cm3/g) and an excellent adsorption selectivity for C2H2/CO2 (11) at room temperature. Furthermore, its discriminatory sorption behavior toward C2H2 and CO2 was probed by computational analysis in detail.

A Homochiral Multifunctional Metal-Organic Framework with Rod-Shaped Secondary Building Units.

A new homochiral multifunctional metal-organic framework, [Zn2(CTBA)2·H2O] (JUC-112), was synthesized under solvothermal conditions, through the design of chiral ligand 4-(3-carboxy-2,2,3-trimethylcyclopentanecarboxamido) benzoic acid (H2CTBA) based on camphoric acid as building block. The crystal structure of the new material is a 2-dimensional (2D) chiral layer packed with infinite rod-shaped secondary building units (SBUs). The homochiral framework was identified by circular dichroism (CD) spectrum. Thermogravimetric measurement indicates its high thermal stability up to 450 °C. In addition, JUC-112 exhibits the capability of separating water from alcohols, second-order nonlinear optical effect, and photoluminescence.

Structural diversity of Zn(II)/Cd(II) coordination polymers constructed from mixed ligand systems of conformationally flexible azo functionalized bis-imidazolate and dicarboxylates

Six coordination polymers based on a conformationally flexible azo functionalized bis-imidazolate ligand bis(3-imidazol-1-ylphenyl)-diazene (L) with diverse conformations, namely, {[ZnL(tp)]·2H2O}n (1), [ZnL(ndc)]n (2), {[ZnL(ip)]·DMF}n (3), [Cd(L)0.5(tp)]n (4), {[CdL(ndc)]·0.625DMF}n (5) and [CdL(ip)]n (6), have been synthesized under solvothermal conditions with the aid of three different dicarboxylic acid ligands (H2tp=terephthalic acid, H2ndc=naphthalene-1,4-dicarboxylic acid, H2ip=isophthalic acid). Complexes 1–3 exhibit 2D+2D→3D polycatenation or 2D→2D interpenetration of (4, 4) sheets with metal ions as 4-connected nodes and ligands as linkers, while the layers are interpenetrated in different ways. Complex 4 possesses an unprecedented self-penetrating framework with a uninodal 8-connected with (416.55.67) topology based on infinite rod-shaped secondary building units (SBUs). Complex 5 displays a 3D 6-connected self-penetrated rob topology constructed from binuclear Cd(II) SBUs. Complex 6 features non-interpenetrated sql topology built on binuclear Cd(II) SBUs. The effects of the conformations of the L ligand, coordination modes of the dicarboxylic acids and metal ions on the diverse structures have been discussed. The thermal stability and luminescent properties of the CPs are also investigated.

A new Cu-based metal-organic framework built upon infinite 1D rod-shaped secondary building units

A new Cu(II) metal-organic framework {[Cu1.5(1,3-bdc)(dtb)(OH)(H2O)](H2O)}n (1) (1,3-H2bdc=1,3-benzenedicarboxylic acid, dtb=1,3-di-(1,2,4-triazole-4-yl)benzene), has been synthesized and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, and IR spectra. Compound 1 features a 3-D open framework constructed by infinite 1D rod-shaped [Cu3(OH)2]n chains as secondary building units. The magnetic property of the complex has also been investigated.

Water-Stable In(III)-Based Metal–Organic Frameworks with Rod-Shaped Secondary Building Units: Single-Crystal to Single-Crystal Transformation and Selective Sorption of C2H2 over CO2 and CH4

Three new water-stable In(III)-based metal-organic frameworks, namely, [In3(TTTA)2(OH)3(H2O)]·(DMA)3 (BUT-70, DMA = N,N-dimethylacetamide), [In3(TTTA)2(CH3O)3] (BUT-70A), and [In3(TTTA)2(OH)3] (BUT-70B), with rod-shaped secondary building units (SBUs) and an new acrylate-based ligand, (2E,2'E,2″E)-3,3',3″-(2,4,6-trimethylbenzene-1,3,5-triyl)-triacrylate (TTTA3-) were obtained and structurally characterized. BUT-70A and -70B were generated in a single-crystal to single-crystal transformation fashion from BUT-70 through guest exchange followed by their removal. The solvents used for guest exchange were methanol and dichloromethane, respectively. Single-crystal structure analyses show that the guest exchange and removal process is accompanied by the substitution of coordinated water molecules of In(III) centers with uncoordinated carboxylate O atoms of TTTA3- ligands. Moreover, hydroxyl groups bridging two In(III) centers are also replaced by methoxyl groups in the transformation from BUT-70 to -70A. Overall, three metal-organic frameworks (MOFs) are constructed by infinite chains consisting of corner-sharing InO4(OR)2 (R = H or Me) octahedral entities, which are interconnected by TTTA3- ligands to form three-dimensional frameworks. Unlike most reported MOFs with infinite chains as SBUs, such as well-known MIL-53 and M-MOF-74, which have one-dimensional channels along the chain direction, the BUT-70 series contain two-dimensional intersecting channels. The Brunauer-Emmett-Teller surface area and pore volume of BUT-70A were estimated to be 460 m2 g-1 and 0.18 cm3 g-1, respectively, which are obviously lower than those of BUT-70B (695 m2 g-1 and 0.29 cm3 g-1). Gas adsorption experiments demonstrated that BUT-70A and -70B are able to selectively adsorb C2H2 over CO2 and CH4. At 1 atm and 298 K, BUT-70A uptakes 3.1 mmol g-1 C2H2, which is 3.6 times that of the CO2 uptake and 7.2 times that of the CH4 uptake. Compared with BUT-70A, BUT-70B presents an even higher C2H2 uptake of 3.9 mmol g-1 at the same conditions, but slightly lower Ideal Adsorbed Solution Theory C2H2/CO2 and C2H2/CH4 selectivities.

Two isostructural fluorinated metal-organic frameworks with rare rod-packing architecture: syntheses, structures and luminescent properties

Abstract Two isostructural fluorinated metal-organic frameworks, formulated as [M 2(Fbix)(1,4-NDC)2] n (M=Cd for 1 and Mn for 2), were synthesized by employing 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) and the flexible fluorinated ligand 2,3,5,6-tetrafluoro-1,4-bis(imidazole-1-yl-methyl)benzene (Fbix) under hydrothermal conditions. Their structures were determined by single-crystal X-ray diffraction and further characterized by infrared spectroscopy, powder X-ray diffraction, and thermogravimetric analyses. Structure analyses have revealed that compounds 1 and 2 show an unusual hex net based on infinite rod-shaped secondary building units. The solid-state fluorescence spectra of 1 and 2 were measured and indicate a ligand-based emission for both complexes.

Two Isostructural Metal–Organic Frameworks Directed by the Different Center Metal Ions, Exhibiting the Ferrimagnetic Behavior and Slow Magnetic Relaxation

Two 3D isostructural metal-organic frameworks with 1D ferrimagnetic chains, formulated as [M3(L)(μ3-OH)2(H2O)4] [H4L = (1,1':4',1″-terphenyl)-2',3,3″,5'-tetracarboxylic acid, where M = Mn for 1 and Co for 2], have been successfully synthesized by employing different center metal ions and a multicarboxylate ligand under identical reaction conditions in this work. The single-crystal X-ray diffraction data of 1 and 2 reveal that the complexes are two 3D isostructural frameworks based on 1D [M3(OH)2]n chains composed of triangular subunits as rod-shaped secondary building units, which are classified as binodal 4,6-connected fry nets with the point symbol (5(10)·6(3)·7(8))(5(4)·6(2)). The magnetic properties revealed that complexes 1 and 2 exhibit ferrimagnetic behavior. Also, the alternating-current susceptibility of 2 displays slow magnetic relaxation, showing interesting magnetic behavior of a single-chain magnet with an effective energy barrier of 32 K.

Dicarboxylate-dependent structural diversity in amino-functionalized complexes: From mononuclear to multinuclear coordination polymer

Three amino-functionalized coordination polymers with different flexible V-shaped dicarboxylate ligands have been synthesized based on Cd salt and a rigid linear ligand L (L=3,6-di(3-imidazolyl)benzene-1,2-diamine, H2HIP=5-hydroxyisophthalic acid, H2ABA=bis(4-carboxylphenyl)amine, H2IBG=isophthaloylbisglycine): {[Cd(L)1.5(HIP)]·(H2O)}n (1), {[Cd2(L)(ABA)2(H2O)]·(H2O)2}n (2) and {[Cd(L)0.5(IBG)]·(H2O)2}n (3). Complex 1 crystallizes in a mononuclear structure with a 3D hxg-d net. Complex 2 crystallizes in a tetranuclear fashion with a layer structure. Complex 3 shows an infinite rod-shaped secondary building unit (SBU) structure. It implies that the structural diversity in assembly process is determined by the flexibility of dicarboxylate ligands. These complexes were characterized by single crystal X-ray diffraction, infrared spectra, thermogravimetric analysis, elemental analysis, and powder X-ray diffraction measurements. Additionally, luminescent properties of 1–3 have also been explored and all exhibit significant red-shifted emission in the solid state at room temperature compared with free L ligand.

Unprecedented Solvent-Dependent Sensitivities in Highly Efficient Detection of Metal Ions and Nitroaromatic Compounds by a Fluorescent Barium Metal-Organic Framework.

The assembly of a fluorescent dicarboxylate ligand with a barium ion resulted in the formation of a 3D metal-organic framework, Ba5(ADDA)5(EtOH)2(H2O)3·5DMF (UPC-17), based on a 1D rod-shaped secondary building unit. The unprecedented solvent-dependent sensitivities of UPC-17 for the detection of Fe(3+)/Al(3+) ions and 4-nitrophenol with high efficiency were observed for the first time. Significantly, UPC-17 exhibits superior "turn-off" detection for the Fe(3+) ion in methanol and acetone emulsions but shows "turn-on" detection in tetrahydrofuran emulsion. Furthermore, the visible color changes in the detection process make them easy to distinguish by the naked eye, which further increases its application potential.

Supramolecular Metal–Organic Frameworks of s- and f-Block Metals: Impact of 1,8-Naphthalimide Functional Group

The new ligand 5-(1,8-naphthalimido)isophthalate (L1352–), containing two carboxylate donor groups and the 1,8-naphthalimide supramolecular tecton, has been used under solvothermal conditions to prepare a series of group 2, lanthanide, and actinide metal complexes: [Ca4(L135)4(H2O)8]·(H2O)9.5(DMF)2.6 (1), Ba(L135)(H2O)1.5(DMF)0.5 (2), La2(L135)3(DMF)4 (3), Ce2(L135)3(DMF)4 (4), Eu2(L135)3(DMF)4 (5), Tb2(L135)3(DMF)4 (6), [UO2(L135)(DMF)]·(py)0.5(EtOH)0.5 (7), and Th(L135)(NO3)2(DMF)2]·(DMF)2 (8). The solid state structure of the calcium complex 1 is based on helical rod-shaped secondary building-units (SBUs) of edge-shared polyhedra bridged by oxygen atoms from the carboxylate groups. The crystals are racemic, with the one-dimensional (1D) helical rods organized by π···π stacking interactions of the naphthalimide group into a three-dimensional (3D) supramolecular metal-organic framework (SMOF) structure. Although the structure of the barium complex 2 also contains rod-shaped SBUs, the rods are linked thro...

Selective Sensing of Fe(3+) and Al(3+) Ions and Detection of 2,4,6-Trinitrophenol by a Water-Stable Terbium-Based Metal-Organic Framework.

A water-stable luminescent terbium-based metal-organic framework (MOF), {[Tb(L1 )1.5 (H2 O)]⋅3 H2 O}n (Tb-MOF), with rod-shaped secondary building units (SBUs) and honeycomb-type tubular channels has been synthesized and structurally characterized by single-crystal X-ray diffraction. The high green emission intensity and the microporous nature of the Tb-MOF indicate that it can potentially be used as a luminescent sensor. In this work, we show that Tb-MOF can selectively sense Fe(3+) and Al(3+) ions from mixed metal ions in water through different detection mechanisms. In addition, it also exhibits high sensitivity for 2,4,6-trinitrophenol (TNP) in the presence of other nitro aromatic compounds in aqueous solution by luminescence quenching experiments.