Jian-Qiang Liu

An Unusual 3D Entangled Co(II) Coordination Polymer Directed by Ferromagnetic Molecular Building Block

A fascinating 3D entangled metal-organic framework, namely, {[Co(2)(bcp)(2)]·3H(2)O}(n) (1), was obtained through the solvothermal generation of flexible and long dicarboxylate (bcp) and metal salt. The crystal structure contains a 1D metal chain with bcp ligands wrapped around it in a wavy line and features an unusual entangled topological net. Furthermore, the magnetic behavior of 1 was also studied and indicated the existence of ferromagnetic interaction and long-range ordering character.

Control over multifarious entangled Co(II) metal–organic frameworks: role of steric bulk and molar ratio of organic ligands

A series of entangled metal–organic polymers, namely [Co(bcp)(bib)]n (1), {[Co(bce)(bib)0.5]·2H2O}n (2), {[Co(oba)(bib)]·H2O}n (3), {[Co(oba)(bib)0.5]·0.5H2O}n (4) and [Co(bce)(bi)0.5]n (5) (H2bcp = 1,3-bis(4-carboxy-phenoxy)propane, H2bce = 1,2-bis(4-carboxy-phenoxy)ethane, H2oba = 4,4′-oxybis(benzoic acid), bib = 1,4-bis(2-methyl-imidazol-1-yl)butane and bi = 1,1′-(1,4-butanediyl)bis(imidazole)), have been synthesized and structurally characterized by single crystal X-ray diffraction. Complexes 1–5 display various coordination motifs with different entangled forms and conformations. The result clearly indicates that the steric bulk effect of ligands is significant in the direction of these networks, which is also well regulated by the molar ratio. In addition, the magnetic behavior of polymers 1–4 are investigated.

Structural variability of Co(II) and Ni(II) entangled metal–organic frameworks: effect of N-donor ligands and metal ions

Through tuning the conformations of N-donor ligands and the coordinative preferences of metal ions, three new metal–organic frameworks with different dimensionalities, namely, {[Co(L1)(bpp)(H2O)]·0.63H2O}n (1), [Ni(L1)(bpp)(H2O)(CH3OH)]n (2) and {Co2(L1)2(bpe)2(H2O)2}·(H2O)(CH3CN)}n (3) (H2L1 = 1,2-bis(4-carboxy-phenoxy)ethane, bpp = 1,3–bis(4-pyridyl)propane and bpe = 1,2–bis(4-pyridyl)ethene), have been synthesized and structurally characterized. Compound 1 exhibits a 2D → 2D parallel interpenetrating motif containing two kinds of double helixes. Polymer 2 displays 2D → 3D interpenetrating framework. Compound 3 is composed of 3D unusual self-interpenetrating net with (4,6)-connected (54·68)(56·65·72·82) topology. This work evidently indicates that the effect of secondary ligands and geometric preferences of metal centers are critical in construction of polymeric arrangement. In addition, the stabilities of these compounds and the magnetic behaviour of 3 are discussed.

Luminescent sensing from a new Zn(II) metal–organic framework

A new metal–organic framework having the formula (NH2(CH3)2)[Zn2(OAc)(L)]·0.5DMF (H4L = 2,5-di(3′,5′-dicarboxylphenyl)pyridine) (GDMU-3) has been synthesized and characterized. The net of GDMU-3 is uninodal and is closely related to the lvt net, which has the same Schlafli symbol of 42·84. GDMU-3 displays selective properties for the detection of nitrobenzene and Fe3+ ions. Remarkably, GDMU-3 exhibits an excellent capability to adsorb methylene blue with high selectivity. The present work indicates that GDMU-3 could be a potential candidate for developing novel luminescence sensors for the selective sensing of nitrobenzene which can be deployed for explosives, Fe3+ and organic dyes.

Rational synthesis of a novel 3,3,5-c polyhedral metal–organic framework with high thermal stability and hydrogen storage capability

By using a functionalized ligand strategy, a novel (3,3,5)-c polyhedron-based metal–organic framework (GDMU-2) with high thermal stability has been constructed. GDMU-2 shows a high H2 uptake of 240.7 cm3 g−1 (2.16 wt%) at 77 K and 1 bar, and also exhibits a good selective adsorption of CO2 over N2 and CH4.

An uncommon (5,5)-connected 3D metal organic material for selective and sensitive sensing of nitroaromatics and ferric ion: experimental studies and theoretical analysis

An unexploited pentacarboxylate ligand, 2,5-bis(3′,5′-dicarboxylphenyl)-benzoic acid (H5L), was designed and used for the preparation of metal organic material using Zn2+ as a node. The new compound, {(Me2NH2)[Zn2(L)(H2O)]·0.5DMF}n (1) (DMF = dimethylformamide), has been synthesized and structurally characterized. The topology of the 5-connected anionic framework may be described as (44)(66) (Schlafli symbol) based on {M2(CO2)5} molecular building blocks (MBBs) and L ligands in 1. It has been demonstrated that 1 can act as a fluorescent sensor for highly sensitive detection of nitroaromatics and Fe3+, with a detection limit of 0.54 ppm for 2,4,6-trinitrophenol (TNP) and 0.81 ppm for Fe3+. The possible emission quenching mechanism in the presence of nitroaromatics has been addressed by theoretical calculations.

Different interpenetrated coordination polymers based on flexible dicarboxylate ligands: topological diversity and magnetism

Through tuning the nature of the secondary ligands, the ligand-to-metal molar ratio and the metal ions, four coordination polymers, namely {[Ni2(bcp)2(4,4′-bipy)2(H2O)4]·3.5H2O}n (1), {[Co2(bcp)2(bpt)2]·2.29H2O·bpt}n (2), [Co2(bcp)2(bib)]n (3) and {[Co(bcp)(2,2′-bipy)(H2O)]·H2O}n (4), have been synthesized and characterized. The structural feature of 1 shows a 3D three-fold parallel interpenetrating framework with CdSO4 topology. 2 exhibits a 2D→3D interpenetrating motif with pseudorotaxane. Compound 3 shows two identical 2D layers with 22·48·65 topology that are interpenetrated in a parallel fashion, resulting in a twofold interpenetrating motif containing polyrotaxane and polycatenane character. However, a 1D zipper-like double-stranded chain is observed in polymer 4. This work evidently indicates that the effect of the secondary ligands and geometric preferences of the metal centers are critical in the construction of the resulting networks. In addition, the magnetic properties of compounds 2 and 3 were also discussed.

Synthesis, structural characterization, and properties of an entangled metal–organic framework based on a flexible dicarboxylate and a rigid N-donor

Self-assembly of manganese acetate with 1,3-bis(4-carboxy-phenoxy)propane (H2bcp) and 1,2-bis(4-pyridyl)ethene (bpe) under solvothermal conditions yielded a polymer {[Mn2(bcp)2(bpe)(DMF)]} n (1), which shows 2-D → 3-D inclined interpenetration with polyrotaxane character. The magnetic behavior of 1 shows antiferromagnetic exchange between Mn magnetic centers.

Luminescent sensing and photocatalytic degradation properties of an uncommon (4,5,5)-connected 3D MOF based on 3,5-di(3′,5′-dicarboxylphenyl)benzoic acid

An uncommon microporous metal–organic framework (MOF), {[Zn5(L)2(DMF)2(μ3-H2O)]·2DMF} (1), was successfully constructed using a less exploited symmetrical pentacarboxylate ligand, 3,5-di(3′,5′-dicarboxylphenyl)benzoic acid (H5L). The MOF 1 features a trinodal (4,5,5)-connected topology having a Schlafli symbol of (42·63·8)(45·65)2(46·64) and is stable in air as well as in acidic/basic aqueous media at room temperature. The MOF 1 behaves as a luminescent sensor for the highly selective and sensitive detection of Fe3+, Fe2+, Cu2+ and Ag+ ions and o-nitrophenol (MNP), p-nitrophenol (PNP), 2,4-dinitrophenol (DNP), 2,4,6-trinitrophenol (TNP) and 4-nitrotoluene (4-NT). Furthermore, the photocatalytic properties of 1 for the degradation of Methyl violet (MV) and Rhodamine B (RhB) have been explored. The possible quenching of the emissions of 1 in the presence of nitroaromatics has been addressed by theoretical calculations and the photocatalytic activity of 1 against organic dyes has been addressed using density of states (DOS) calculations.

Fluorescence detection of Mn2+, Cr2O72− and nitroexplosives and photocatalytic degradation of methyl violet and rhodamine B based on two stable metal–organic frameworks

The reaction of Zn(NO3)2·6H2O/Cd(NO3)2·4H2O with a semi-flexible ligand 4′-(4-(3,5-dicarboxylphenoxy)phenyl)-4,2′:6′,4′′-terpyridine (H2dbp) gave two new metal–organic frameworks of [Zn(dbp)]n (1) and [Cd(dbp)(H2O)·2H2O·CH3CN]n (2). Single crystal X-ray diffraction analyses reveal that both 1 and 2 show three-dimensional, two-fold interpenetrating four-connected networks with 44.610.8 topology. The photoluminescence investigation indicates that both 1 and 2 could be prospective candidates for developing luminescence sensors for the sensing of Mn2+, Cr2O72− and nitroaromatic analytes. Furthermore, the photocatalysis properties of 1–2 for the degradation of methyl violet and rhodamine B were examined.