Tricarboxylate Ligand Research Articles

A Versatile Al(III) -Based Metal-Organic Framework with High Physicochemical Stability.

A unique Al(III) -based metal-organic framework (467-MOF) with two types of square channels has been designed and synthesized by using a flexible tricarboxylate ligand under solvothermal conditions. 467-MOF exhibits superior thermal and chemical stability and, moreover, shows high CO2 sorption selectivity over H2 , with a selectivity, based on the ideal adsorbed solution theory (IAST) of approximately 45 at 273 or 293 K. Furthermore, its solvent-dependent photoluminescence makes it an applicable sensor in the detection of nitrobenzene explosives through fluorescence quenching.

Lanthanide-tricarboxylate frameworks: Synthesis, structure and photoluminescence property

Reactions of tricarboxylate ligands biphenyl-3,4′,5-tricarboxylic acid (H3L1) and [1,1′:3′,1″-terphenyl]-4,4″,5′-tricarboxylic acid (H3L2) with the lanthanide metal salts under solvothermal conditions give rise to five new lanthanide-organic frameworks. Complexes {[Ln(L1)(H2O)(DMF)]·DMF·H2O}n [Ln = La (1), Ce (2) and Sm (3)] with (L1)3− have the same framework structures, while the frameworks based on the ligand (L2)3− with formula {[Ln(L2)(H2O)2]·2DMF·14H2O}n [Ln = Sm (4) and Gd (5)] are also isostructural. All the complexes have binuclear paddlewheel [Ln2(CO2)4] clusters as the secondary building units, which are further linked together by the organic ligands to form three-dimensional (3,6)-connected frameworks. In addition, thermal stability and photoluminescence properties of 1–5 were investigated.

Porous Cadmium(II) Anionic Metal–Organic Frameworks Based on Aromatic Tricarboxylate Ligands: Encapsulation of Protonated Flexible Bis(2-methylimidazolyl) Ligands and Proton Conductivity

Two porous 3-D anionic metal–organic frameworks (MOFs) containing protonated bmib, [Cd2(btc)2(H2O)2]n·n(H2bmib)·6n(H2O) (1) and [Cd4(cpip)2(Hcpip)2]n·n(H2bmib)·n(H2O) (2), have been prepared by hydrothermal reactions of Cd(NO3)2·4H2O, 1,4-bis(2-methylimidazol-1′-yl)butane (bmib) with 1,3,5-benzenetricarboxylic acid (H3btc) and 5-(4-carboxyphenoxy)isophthalic acid (H3cpip), respectively. Complexes 1 and 2 are 3-D anionic frameworks containing 1-D channels and consisting of tetranuclear Cd(II)-carboxylate units, respectively. H2bmib and lattice water molecules are located in their void spaces and form extensive hydrogen bonds and C–H···π interaction with the anionic frameworks. TGA studies and XRD patterns show the anionic frameworks of 1 and 2 are intact after the removal of lattice water molecules. The luminescent emission of 1 and 2 shows an obvious red shift in comparison with free H3btc and H3cpip, respectively. Complexes 1 and 2 possess proton conduction owing to the presence of the extensive hydrogen...

Synthesis, Structures, and Luminescent Properties of Three Coordination Polymers Constructed from Tricarboxylate and Bisbenzoimidazole Ligand

AbstractThe hydrothermal reaction of the tricarboxylate ligand 5‐(carboxymethoxy)isophthalic acid (H3L) with ZnII, CdII, and SnII salts in the presence of the bisbenzoimidazole coligand 1, 3‐bis(benzimidazol‐2‐yl)‐2‐oxapropane (bbop) afforded the coordination polymers, [Zn(HL)(bbop)]n (1), [Cd(HL)(bbop)]n (2), and {[H2(bbop)][Sn2L2]}n (3). The complexes were characterized by elemental analyses, IR spectroscopy, single‐crystal X‐ray diffraction analyses, thermogravimetric analyses, and fluorescence properties. The structures of complexes 1 and 2 are constructed by 1D chains and show strong blue luminescence emission. The structure of complex 3 is a 2D anionic dilayer, and shows a vase‐like porous structure occupied by the bulky [H2(bbop)]2+ cation, which is an uncommon structural feature in transition metal coordination polymers. The three complexes are further connected by hydrogen bonds to form 3D supramolecular architectures.

An unusual 2D nanoscaled quadruple-layer metal–organic framework based on octanuclear cobalt clusters

Self-assembly of a flexible tricarboxylate ligand (H3L) and cobalt salt under hydrothermal conditions yields an unprecedented two-dimensional (2D) nanoscaled quadruple-layer networks [Co4(HL)3(μ3-OH)2(H2O)2]·5H2O (1) (H3L=(3,5-dicarboxyl-phenyl)-(4-(2′-carboxyl-phenyl)-benzyl)ether). The structure of compound 1 was determined by single-crystal X-ray diffraction analysis and further characterized by elemental analyses, IR spectrum, and thermogravimetric analysis. Compound 1 represents the first 2D nanoscaled multiple-layer architecture constructed from octanuclear cobalt cluster building blocks. Furthermore, the adjacent sidearm-containing 2D quadruple-layer motifs are interdigitated in a mutual relationship to form a 3D supramolecular framework. In addition, the magnetic properties of compound 1 have been studied by measuring its magnetic susceptibility in the temperature range of 2–300K, indicating the existence of antiferromagnetic coupling within the octanuclear cobalt cluster.

Hierarchical heteroaggregation of binary metal-organic gels with tunable porosity and mixed valence metal sites for removal of dyes in water.

Hierarchical heteronuclear metal-organic gels (MOGs) based on iron (Fe) and aluminium (Al) metal-organic framework (MOF) backbones bridged by tri-carboxylate ligands have firstly been synthesized by simple solvothermal method. Monometallic MOGs based on Fe or Al give homogenous monoliths, which have been tuned by introduction of heterogeneity in the system (mismatched growth). The developed gels demonstrate that surface areas, pore volumes and pore sizes can be readily tuned by optimizing heterogeneity. The work also elaborates effect of heterogeneity on size of MOG particles which increase substantially with increasing heterogeneity as well as obtaining mixed valence sites in the gels. High surface areas (1861 m2/g) and pore volumes (9.737 cc/g) were obtained for heterogeneous gels (0.5Fe-0.5Al). The large uptakes of dye molecules (290 mg/g rhodamine B and 265 mg/g methyl orange) with fast sorption kinetics in both neutral and acidic mediums show good stability and accessibility of MOG channels (micro and meso-/macropores), further demonstrating their potential applications in catalysis and sorption of large molecules.

Quest for highly connected metal-organic framework platforms: rare-earth polynuclear clusters versatility meets net topology needs.

Gaining control over the assembly of highly porous rare-earth (RE) based metal-organic frameworks (MOFs) remains challenging. Here we report the latest discoveries on our continuous quest for highly connected nets. The topological exploration based on the noncompatibility of a 12-connected RE polynuclear carboxylate-based cluster, points of extension matching the 12 vertices of the cuboctahedron (cuo), with 3-connected organic ligands led to the discovery of two fascinating and highly connected minimal edge-transitive nets, pek and aea. The reduced symmetry of the employed triangular tricarboxylate ligand, as compared to the prototype highly symmetrical 1,3,5-benzene(tris)benzoic acid guided the concurrent occurrence of nonanuclear [RE9(μ3-OH)12(μ3-O)2(O2C-)12] and hexanuclear [RE6(OH)8(O2C-)8] carboxylate-based clusters as 12-connected and 8-connected molecular building blocks in the structure of a 3-periodic pek-MOF based on a novel (3,8,12)-c trinodal net. The use of a tricarboxylate ligand with modified angles between carboxylate moieties led to the formation of a second MOF containing solely nonanuclear clusters and exhibiting once more a novel and a highly connected (3,12,12)-c trinodal net with aea topology. Notably, it is the first time that RE-MOFs with double six-membered ring (d6R) secondary building units are isolated, representing therefore a critical step forward toward the design of novel and highly coordinated materials using the supermolecular building layer approach while considering the d6Rs as building pillars. Lastly, the potential of these new MOFs for gas separation/storage was investigated by performing gas adsorption studies of various probe gas molecules over a wide range of pressures. Noticeably, pek-MOF-1 showed excellent volumetric CO2 and CH4 uptakes at high pressures.

PH-Specific Crystalline Binary and Ternary Metal–Organic Framework Materials of Pb(II) with (Di)Tricarboxylate Ligands and N,N′-Aromatic Chelators. Structure, Architecture-Lattice Dimensionality, and Electronic Spectroscopic Property Correlations

Efforts to probe and delineate intricate structure–property relationships key to the development of crystalline Pb(II)-containing metal–organic framework materials led to the design and pH-specific hydrothermal synthetic investigation of binary/ternary Pb(II)-(di)tricarboxylate ligand (succinic, glutaric, tricarballylic acids) systems in the presence of variable-nature aromatic N,N′-chelators bipyridine (bpy)/phenanthroline (phen). The arisen crystalline materials [Pb(phen)(suc)]n (1), [Pb3(phen)3(glu)3]n·7nH2O (2), [Pb3(tca)2]n (3), and [Pb2(phen)2(tcaH)2]n·nH2O (4) provide evidence for structural correlations linking the nature of ligands with Pb(II) chemistry and the emerging crystalline-polymeric assemblies. Detailed physicochemical characterization (Fourier transform infrared spectroscopy, 13C-,207Pb-cross polarization magic angle spinning NMR, thermogravimetric analysis, luminescence) reveals distinct architecture, lattice dimensionality (2D-3D), and luminescence property correlations and identifies structural and electronic factors interweaving into the design of functional materials.

Two new pH-controlled coordination polymers constructed from an asymmetrical tricarboxylate ligand and Zn-based rod-shaped SBUs

Two new 3D coordination polymers, [Zn3(L)2(H2O)4]·H2O (1) and [Zn5(μ3-OH)4(L)2(H2O)2] (2) (H3L=3-(2′,5′-dicarboxylphenyl)benzoic acid), have been synthesized under hydrothermal conditions by adding different amounts of NaOH. Structural analyses show that both of them contain 1D inorganic Zn(II)-chains as rod-shaped secondary building units (SBUs) but they are in different forms. The rod-shaped Zn(II)-chain of 1 is only Zn-carboxylate chain, while the one in 2 is formed by the independent Zn5(COO)6 clusters connected by hydroxyl oxygen. Furthermore, the thermal and luminescent properties of both compounds have been studied.

A tetranuclear [Co4] cluster-based metal–organic framework: Synthesis, structure and magnetic property

A CoII coordination polymer, {[Co4(CIPA)2(μ3-OH)2(H2O)4]·4H2O}n (1), based on a tri-carboxylate ligand (H3CIPA=5-acetyloxybenzene −1,3-dicarboxylic acid) has been obtained and characterized structurally. Compound 1 displays a two-dimensional (2D) framework based on [Co4] clusters. Thermogravimetric analysis suggests high thermal stability of compound 1, and magnetic properties measurement indicates that antiferromagnetic couplings exist between neighboring CoII centers.

Robust metal–organic framework with [Mn3] clusters: Synthesis, structure and magnetic property

In this work, one novel three dimensional non-interpenetrated metal–organic framework {[Mn3(L)2(H2O)4]·2H2O·2DMF}n (1) was synthesized by a new tri-carboxylic ligand (H3L=3,5-Bis-[2-(4-carboxy-phenoxy)-ethoxy]-benzoic acid). Single crystal structural determination revealed that compound 1 possesses a stable 3D framework, containing linear tri-nuclear [Mn3] cluster as a node. The investigation on PXRD patterns in various solvents and TGA displays excellent solvents and thermal stability. Additionally, magnetic measurements indicate that antiferromagnetic interactions exist within compound 1.

A luminescent cadmium metal-organic framework for sensing of nitroaromatic explosives.

A novel metal–organic framework [Cd3(TPT)2(DMF)2]·(H2O)0.5 (1) has been solvothermally synthesized using a new rigid unsymmetrical tricarboxylate ligand p-terphenyl-3,4′′,5-tricarboxylic acid (H3TPT). Single-crystal X-ray diffraction analysis reveals that 1 possesses a three-dimensional (3D) framework with an alb-4,8-C2/c topology constructed by the combination of Cd–carboxylate chains and TPT linkers. The π-electron rich ligand H3TPT enables 1 to have an excellent luminescent property. The micrometer-sized compound 1′ dispersed in ethanol exhibits high efficiency detection for picric acid (PA). The high efficiency, stability and recyclability of 1′ make it a potential chemosensor for nitroaromatic explosives.

A microporous lanthanum metal-organic framework as a bi-functional chemosensor for the detection of picric acid and Fe(3+) ions.

A microporous lanthanum metal-organic framework [La(TPT)(DMSO)2]·H2O (La-MOF ()), has been synthesized using a rigid unsymmetrical tricarboxylate ligand of p-terphenyl-3,4'',5-tricarboxylic acid (H3TPT). The structure of is constructed by bi-nuclear lanthanum clusters and fully deprotonated TPT(3-) ligands, which can be simplified into a 3,6-connected flu-3,6-C2/c topology with a point symbol of (4(4)·6)2(4·6(2)·8(7)·10(2)). The π-electron rich ligand H3TPT enables to have blue luminescence when excited at 342 nm at ambient temperature. Meanwhile, exhibits the selective detection of picric acid (PA) and Fe(3+) ions in ethanol solution over other nitroaromatic compounds and metal ions. The high quenching efficiency and selectivity of makes it a potential bi-functional chemosensor for both PA and Fe(3+) ions.

A luminescent microporous metal-organic framework with highly selective CO₂ adsorption and sensing of nitro explosives.

A luminescent microporous metal-organic framework based on a π-electron-rich tricarboxylate ligand and an In(3+) ion has been solvothermally obtained and characterized and exhibits highly selective CO2 adsorption over CH4 and N2 gases and selective sensing of the nitro explosive 2,4,6-trinitrophenol.

Synthesis, Structures, and Photoluminescent Properties of Three Coordination Polymers based on an Asymmetric Semi‐rigid V‐shaped Tricarboxylate Ligand

AbstractThree coordination polymers, [Zn(HL)(phen)(H2O)]n (1), [Zn1.5(L)(4, 4′‐bpy)1.5]n·4nH2O (2), and [Zn2(HL)2(bib)2]n·2nH2O (3), were assembled from the asymmetric semi‐rigid V‐shaped tricarboxylate ligand 4‐(2‐carboxy‐phenoxy)‐isophthalic acid (H3L) with 1, 10‐phenanthroline (phen), 4, 4′‐bipyridine(4, 4′‐bpy) and 1, 4‐bis (imidazol‐1‐yl) benzene (bib) as auxiliary ligands. Complex 1 features a one‐dimensional (1D) double‐looped chain, which is further extended into a 2D supramolecular layer via two kinds of hydrogen‐bonding interactions. Complex 2 exhibits a complicated 3D framework, which can be rationalized as a (3, 4,4)‐connected trinodal net with a unique (4·8·10) (4·8·10·123) (82·122·14·16) topology. Complex 3 has a two‐dimensional (2D) (4, 4) layer formed by the {Zn2} dinuclear SUBs and the bib ligands. The structural and topological differences of the three complexes indicate that the N‐containing auxiliary ligands play important roles in the formation of the final framework structures. In addition, complexes 1–3 were characterized by elemental analysis, IR spectroscopy, and X‐ray powder diffraction. The thermal behaviors and luminescent properties of complexes 1–3 were also investigated in detail.

Structural Diversity of MOFs Constructed by Tricarboxylate Ligand

Considerable progress has been made in the construction of metal-organic frameworks (MOFs) recently[1]. Due to the close relationship between the structures of MOFs and their properties, tuning structures by rational design through the judicious choice of metal ions, bridging organic ligands and reaction conditions becomes very attractive[2]. Three-dimensional pillar-layer architecture of [Co3L2(bpe)4]·2DMF·2(H2O)] (complex 1, Fig 1a), honeycomb-like channels of [Zn2L(OH)(bpe)]·5.5(H2O)] (complex 2,Fig 1b), and chain-like structure of [Zn2(HL)2(bpy)2(H2O)])2]·(bpy)·6(H2O)] (complex 3, Fig 1c) (HL3>=5-(4-carboxybenzoylamino-isophthalic acid), bpe = 1,2-bis(4-pyridyl)ethane and bpy = 4,4'-bipyridine and) have been synthesized and characterized by single X-ray crystallography(Figure 1). Complex 1 features a three-dimensional (3D) pillar-layer architecture generated from bpe-pillared M-L3-layers. Complex 2 is a 3D structure with 4- and 6-coordinated Zn2+in the centrosymmetric tetranuclear Zn4(µ3OH)2(COO)6(bpe)4SBU. Complex 3 is 2D structure. The [Zn(HL)(bpy)(H2O)] chains are connected each other by hydrogen bonding, with free bpy and guest water molecules accommodated in.

Porous zirconium metal-organic framework constructed from 2D → 3D interpenetration based on a 3,6-connected kgd net.

A new porous zirconium metal-organic framework (Zr MOF), Zr6(μ3-O)4(μ3-OH)4(OH)6(H2O)6(BTB)2·6DMF·H2O (1; H3BTB = 5'-(4-carboxyphenyl)[1,1':3',1″-terphenyl]-4,4″-dicarboxylic acid), based on Zr6 clusters and tricarboxylate ligands has been constructed and characterized. The Zr6 clusters were linked by BTB ligands to generate a 2D network of kgd topology. The interpenetrations among the 2D networks gave rise to a 3D porous framework, which represents the first Zr MOF constructed from 2D → 3D interpenetration. The gas uptake and catalytic properties for 1 have also been studied.

Preparation of composite membranes on a ceramic base with supported metal-organic framework structure of MOF-199 and study of their adsorption properties

A method for preparing composite membranes based on MOF-199 with copper ions and tricarboxylate ligands via creating nucleation sites on the surface of the ceramic substrate, followed by grafting tricarboxylic acid to the surface of the ceramic porous substrate (γ-Al2O3), is developed. The permeability of the membranes is measured and the separation of a mixture of ethane and methane on them is performed. The influence of the method of forming a metal-organic framework structure (MOF) on the sorption properties of composite membranes is ascertained.

Metal Ion-Driven Assembly of Two New Coordination Polymers Constructed by Asymmetric Tricarboxylate and Imidazole-Containing Ligands: Syntheses, Crystal Structures, and Luminescent Properties

Two new coordination polymers, namely, {[Cd3(bpt)2(bimb)2]·2(H2O)}n (1) and [Zn3(bpt)2(bimb)2]n (2) (bpt = biphenyl-3,4′,5-tricarboxylate, bimb = 1,4-bis(1-imidazol-yl)-2,5-dimethyl benzene), have been obtained under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analysis and further characterised by elemental analysis and infrared spectroscopy. Complex 1 exhibits a trinodal (4,4,4)-connected topology with Schläfli symbol of (4.62.83)4.(64.82). Complex 2 is also a three-dimensional structure and displays a (3,4,6)-connected topology with Schläfli symbol of (4.62)2.(42.66.85.102).(64.82). It is shown that the asymmetrically tricarboxylate can bear diverse structures regulated by metal ions. The photoluminescence behaviours of compounds 1 and 2 were also discussed.

Structures, photoluminescence and heterogeneous catalysis of five metal complexes constructed by a flexible tricarboxylate ligand

Five isostructural complexes constructed with H3TTTA and 4,4′-bpy, namely Co(H2TTTA)2(4,4′-bpy)2 (1), Ni(H2TTTA)2(4,4′-bpy)2 (2), Mn(H2TTTA)2(4,4′-bpy)2 (3), Cd(H2TTTA)2 (4,4′-bpy)2 (4) and Cu(H2TTTA)2(4,4′-bpy)2 (5) (H3TTTA=2,2′, 2″-[1,3,5-triazine-2,4,6-triyltris(thio)] tris–acetic acid, 4,4′-bpy=4,4′-dipyridine), have been synthesized and characterized by elemental analysis, IR, XRD and single crystal X-ray diffraction. The strong O–H⋯N and O–H⋯O stacking interactions link the molecules into a 2D network. Moreover, these 2D networks are connected into 3D frameworks through C–H⋯O and C–H⋯N stacking interactions, which seem to be effective in stabilizing the crystal structures. Complexes 1–5 have been tested for their catalytic properties. The results indicate that all the complexes show good catalytic activities for the cyanosilylation of benzaldehyde, whilst the Mn complex (3) shows a much better conversion for the cyanosilylation of acetophenone than the other complexes. The fluorescence properties of the complexes have also been investigated in detail.