A pair of novel Zn(ii) enantiomeric coordination polymers based on a chiral multicarboxylate ligand: synthesis, crystal structures and molecular recognition properties

A pair of Zn(ii) enantiomeric coordination polymers, 1-R and 1-S, were synthesized via solvothermal reactions, exhibiting luminescence recognizing properties toward nitro aromatic compounds and ferric cations.

A Ni-based MOF for selective detection and removal of Hg2+ in aqueous medium: a facile strategy

A Ni-based 3D MOF, [Ni(3-bpd)₂(NCS)₂]_n, where 3-bpd is 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene, has been explored for simultaneous detection and removal of Hg²⁺ in aqueous medium with excellent Hg uptake capacity.

A rare Pb9 cluster-organic framework constructed from a flexible cyclotriphosphazene-functionalized hexacarboxylate exhibiting selective gas separation

A rare Pb₉ cluster-based organic framework constructed from a flexible cyclotriphosphazene-functionalized hexacarboxylate exhibits selective adsorption separation of C₂ hydrocarbons and CO₂ from CH₄ under ambient conditions.

Two metal–organic frameworks based on a flexible benzimidazole carboxylic acid ligand: selective gas sorption and luminescence

Two new 3D frameworks with a novel (3,4,7)-connected trinodal net and (3,6)-connected binodal net were obtained by using a flexible ligand, showing significant adsorption selectivity for CO₂ over CH₄ as well as strong luminescence.

Controllable assembly of Cu(ii) coordination compounds based on a flexible zwitterionic benzimidazole–dicarboxylate ligand: synthesis, structural diversity, reversible SCSC transformation and magnetic properties

The reversible SCSC transformation of a paddle-wheel cluster to a 1D linear polymer could be accomplished.

In-MOFs based on amide functionalised flexible linkers

Two new amide functionalised metal–organic frameworks, In(OH)CSA and In(OH)PDG, were synthesized using two flexible linkers, N-(4-carboxyphenyl)succinamic acid (CSA) and N,N′-(1,4-phenylenedicarbonyl)diglycine (PDG), respectively. Both structures consist of corner-sharing {InO₄(OH)₂} octahedra in the form of trans indium hydroxide chains, which are interconnected by the dicarboxylate linkers to form stacked 2-dimensional layers. The different symmetries and configurations of the flexible and rigid features on the linkers results in different supramolecular interactions dominating between linkers, resulting in different shaped pores and functional group orientation. In(OH)CSA lacks hydrogen bonding between linkers, which results in close packing between the layers and very small solvent accessible pores running perpendicular to the plane of the layers. In(OH)PDG exhibits strong intra- and interlayer hydrogen bonding, which prevents the layers from close packing and results in larger cylindrical pores running parallel to the indium hydroxide chains, producing a total accessible volume of 25% of the unit cell volume.

Synthesis, characterization, and in vitro evaluation of a radio-metal organic framework composed of in vivo generator 166Dy/166Ho and DOTMP as a novel agent for bone marrow ablation

In this study, the MOF concept contributed to the preparation of a novel, bone-ablating agent composed of Cu(II) using the in vivo generator 166Dy/166Ho and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene phosphonic acid (DOTMP). The product was characterized (IR, elemental analysis: CHN, ICM-MS, PIXE, DLS, XRD) and quality-controlled (radio-thin layer chromatography (RTLC)). The stability and in vitro hydroxyapatite binding was checked up to one week at 37°C in human serum. Radio-MOF crystals and colloidal radio-MOF particles were obtained by varying the synthesizing conditions (including pH and temperature), and they had similar IR patterns and similar elemental analysis results. The estimated chemical formula was [1Lu-1Cu-1Cl-1DOTMP] for both. The final product was synthesized at pH = 8 while stirring at room temperature using 166Dy/166Ho-nitrate, CuCl2, and DOTMP (yield > 99%, RTLC). Dynamic light scattering (DLS) measurements showed particles in the size range of 60 to 100 nm for the resultant radio-MOF particles (RMP). In vitro binding experiments showed acceptable bone-seeking affinity of the prepared formula even after one week of storage in human serum at 37°C. Importantly, this is the first study of the use of the MOF concept to provide a highly-stable organometallic compound containing 166Dy/166Ho in vivo generator for bone marrow ablation.

Moisture-Stable Zn(II) Metal-Organic Framework as a Multifunctional Platform for Highly Efficient CO2 Capture and Nitro Pollutant Vapor Detection

A moisture-stable three-dimensional (3D) metal-organic framework (MOF), {(Me2NH2)[Zn2(bpydb)2(ATZ)](DMA)(NMF)2}n (1, where bpydb = 4,4'-(4,4'-bipyridine-2,6-diyl)dibenzoate, ATZ = deprotonated 5-aminotetrazole, DMA = N,N-dimethylacetamide, and NMF = N-methylformamide), with uncoordinated N-donor sites and charged framework skeleton was fabricated. This MOF exhibits interesting structural dynamic upon CO2 sorption at 195 K and high CO2/N2 (127) and CO2/CH4 (131) sorption selectivity at 298 K and 1 bar. Particularly, its CO2/CH4 selectivity is among the highest MOFs for selective CO2 separation. The results of Grand Canonical Monte Carlo (GCMC) simulation indicate that the polar framework contributes to the strong framework-CO2 binding at zero loading, and the tetrazole pillar contributes to the high CO2 uptake capacity at high loading. Furthermore, the solvent-responsive luminescent properties of 1 indicate that it could be utilized as a fluorescent sensor to detect trace amounts of nitrobenzene in both solvent and vapor systems.

Internal dynamics and guest binding of a sterically overcrowded host

Substituent control in self-assembled host systems allows for a fine-tuning of structure, dynamics and guest preference. Flat banana-shaped ligands L1 assemble with Pd(ii) cations into the interpenetrated coordination cage dimer [3BF4@Pd4L18], capable of sequential guest uptake. In contrast, the introduction of bulky adamantyl groups in ligand L2 prevents dimerization and results in the clean formation of monomeric cage species [Pd2L24]. Owing to steric crowding, the adamantyl substituent is considerably bent sideways with respect to the ligand backbone, and is rapidly flipping between both faces of the free ligand giving rise to two energetically degenerate conformers. Surprisingly, the flipping is preserved in the cage, albeit at a lower rate due to entropic reasons. Despite the very dense packing within the self-assembled structure, the cage is able to encapsulate a series of bis-anionic guests in an induced-fit fashion. Electronic structure calculations revealed a substantial contribution from dispersion interactions between the guest and the surrounding adamantyl groups that stabilize the host-guest complex. Guest exchange kinetics were quantified and the influence that encapsulated guests imparted on the ligand flipping dynamics was examined by a series of 2D NMR experiments. Four synchrotron X-ray structures of the cage and its host-guest complexes are presented, allowing for unprecedented insight into the host-guest interactions of a sterically overcrowded host and its guest-induced distortion.

Synthesis, crystal structures, and thermal and spectroscopic properties of two Cd(II) metal-organic frameworks with a versatile ligand

Two new metal-organic frameworks, namely, [Cd(L)(H2O)] n (1) and {[Cd0.5(L)(4,4′-bipy)0.5][Cd0.5(H2O)(4,4′-bipy)0.5]·H2O} n (2), where H2L = N-pyrazinesulfonyl-glycine and 4,4′-bipy = 4,4′-bipyridine, have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental, thermogravimetric, and photoluminescent analysis. X-ray diffraction crystallographic analyses indicate that 1 displays a distorted octahedral metal coordination in a 3-connected (4, 82) topology, while the molecular structure of 2 has a 4-connected (4, 4) topology with two perfectly octahedrally coordinated Cd centers. The L2– ligand serves as a N,N,O-tridentate, μ 2-pyrazine-bridging, and μ 2-carboxylate-bridging ligand in 1, and as a N,O-bidentate and μ 2-carboxylate-bridging ligand in 2. In the crystal, a 3D supramolecular architecture is formed by O–H···O hydrogen bond interactions in 1, but through O–H···O as well as π···π stacking in 2. The two compounds show intense fluorescence in the solid state at room temperature.

Hydrothermal synthesis and structural characterization of metal-organic frameworks based on new tetradentate ligands

The hydrothermal reaction of two new tetradentate ligands with different metal salts of cadmium nitrate, zinc chloride, cobalt nitrate and deprotonated terephthalic acid (H2tp), isophthalic acid (H2ip), 4,4'-oxybisbenzoic acid (H2obba) in H2O/DMF or H2O/methanol gave three metal-organic frameworks (MOFs): {[Zn2(L1)(tp)(formate)2]·H2O}n (), {[Cd2(L2)(ip)2]·2H2O}n (), {[Co2(L2)(obba)2]}n () (L1 = 1,2-bis {2,6-bis [(1H-imidazol-1-yl) methyl]-4-methylphenoxy} ethane, L2 = 1,3-bis {2,6-bis [(1H-imidazol-1-yl) methyl]-4-methylphenoxy} propane). The structures of the frameworks are established by single-crystal X-ray diffraction. Compound is a three-dimensional (3D) framework with a 2-fold interpenetrated form, which exhibits a 2-nodal (3,4)-connected fsh-3,4-P21/c net with a {8(3)}2{8(5)·10} topology. Compound has a 2-nodal (4,8)-connected 3D framework where the dinuclear cadmium cluster secondary building units (SBUs) assemble with isophthalate and ligand L2 to construct a rare topological type sqc22 net with a {3(2)·5(4)}{3(4)·4(4)·5(10)·6(10)} topology. Whereas, Compound can be extended to a 2D interlocked (4,4)-connected 4,4 L28 net with the point symbol {4·6(4)·8}2{4(2)·6(4)}. L1 and L2 are tetradentate ligands with diverse linkers and display different coordination modes. In addition, the thermal stability and photochemical properties of the frameworks are also investigated.

Water-Stable Anionic Metal-Organic Framework for Highly Selective Separation of Methane from Natural Gas and Pyrolysis Gas

A 3D water-stable anionic metal-organic framework [Zn4(hpdia)2]·[NH2(CH3)2]·3DMF·4H2O (FJI-C4) was constructed based on an elaborate phosphorus-containing ligand 5,5'-(hydroxyphosphoryl)diisophthalic acid (H5hpdia). FJI-C4 with narrow one-dimensional (1D) pore channels exhibits high selectivity of C3H8/CH4 and C2H2/CH4. It is the first time for the MOF which contains phosphorus for selective separation of methane from natural gas and pyrolysis gas.

Crystal structure and photoluminescence properties of a new CdIIcoordination polymercatena-poly[bis[4-bromo-2-({[2-(pyrrolidin-1-yl)ethyl]imino}methyl)phenolato-κ3N,N′,O]di-μ3-chlorido-di-μ2-chlorido-bis(methanol-κO)tricadmium(II)]

Schiff base–metal complexes have been used widely as catalysts for many organic reactions, such as ring-opening polymerization and oxidation. In view of the importance of CdIIcoordination polymers and in an effort to enlarge the library of such complexes, the title novel polymeric CdIItridentate Schiff base complex, [Cd3(C13H16BrN2O)2Cl4(CH4O)2]n, has been synthesized and characterized by elemental analyses, UV and IR spectroscopies, and single-crystal X-ray diffraction. The complex crystallizes in the triclinicP\overline{1} space group with two symmetry-independent CdIIatoms, one of which lies on an inversion centre, and analysis of the crystal structure shows that both CdIIatoms are six-coordinated; the environment around one CdIIatom can be described as distorted octahedral, while that around the second CdIIatom is octahedral. The CdIIatoms are linked by chloride ligands to form a one-dimensional coordination polymer. The nonbonding intermolecular Cd...Cd distances are 3.7009 (4) and 4.3563 (5) Å. Furthermore, the photoluminescence properties of the complex have been investigated and it displays a strong red emission in the solid state at room temperature.