3D Polycatenation Research Articles

Selective Detection of Primary Aromatic Amines through Enhanced Luminescence of a 2D + 2D Inclined Polycatenated Microporous Nitro-Functionalized Metal-Organic Framework.

Detection and sensing of amines through enhanced fluorescence emission are always challenging in aqueous solution. The range of different Lewis basicities, shapes, and sizes as well as the different structural arrangements of amines is responsible for their less specificity in aqueous solution. Here, we have designed a highly fluorescent emissive 2D + 2D → 3D inclined polycatenated NO2-functionalized flexible metal-organic framework (MOF) for selective segregation of electron-rich aromatic primary amines from electron-deficient amines in aqueous solution, showing different emission behaviors. The inclined polycatenated 2D + 2D → 3D MOF having an asymmetric unit {[Cd(dim)(2-nta)(H2O)](H2O)(MeOH)}n (1) has been synthesized by a slow diffusion process and characterized thoroughly by single-crystal and powder X-ray diffraction (PXRD) as well as other physicochemical methods. The desolvated species of 1 (Ref. MOF) is found to be stable and has been characterized by PXRD and adsorption study. The fluorescence profile of the Ref. MOF shows selective enhancement in the presence of electron-rich primary aromatic amines, while the same shows quenching for electron-deficient amines in aqueous solution. The Ref. MOF reported here consists of flexible space between two 2D layers that is responsible for different orientations for different analyte primary aromatic amines (PAAs) with different sizes. The above findings are also supported by time-resolved fluorescence spectroscopy. The respective fluorescence enhancement and quenching have been explained by the interaction between the CB of the host MOF and LUMO of guest amines. Therefore, this work presents an operable method for the sensing of PAAs using a single compound, which is a polycatenated MOF.

Structural diversity and luminescence of zinc coordination polymers constructed by flexible ligands

Three new zinc coordination polymers based on the flexible ligand L (5,5′-((1,3-phenylenebis(methylene))bis(oxy))diisophthalic acid) have been prepared by solvothermal synthesis, which was named for [Zn4(L)2(pdp)(H2O)5]n (1), {[Zn(L)0.5(pdp)]·(NMP)0.5}n (2) and {[Zn(L)0.5(bpp)]·3H2O}n (3) (pdp=trans-1,2-bis(4-pyridyl)ethylene), bpp = 4,4′-(1,3-propanediyl)bis-pyridine) respectively. By controlling the length of auxiliary ligands, compounds 1 and 3 can be assembled under similar reaction conditions with different 3D structures. Although the ligands are all achiral components, it is interesting to note that compound 1 crystallizes in P21 chiral space group. The two Zn ions are in an asymmetric coordination environment resulting in symmetric breaking, which might be the reason compound 1 crystallizes in the chiral space group. While, compound 3 is composed of two identical 2D layers interpenetrating with each other, displaying a 2D + 2D → 3D polycatenation network. By changing the solvent and temperature, compound 2 can be available which presents a 3D structure with a two-fold interpenetrating framework, and the guest accessible volume (2414 Å3 per unit cell) accounts for 16.8% of the unit cell volume. In addition, compounds 1–3 have also had their solid-state luminescence characteristics, powder X-ray diffraction, and thermal stabilities examined.

Experimental and theoretical investigation on the hydrochromic property of a Ni(II)-containing coordination polymer with an inclined 2D → 3D polycatenation architecture

In recent years, hydrochromic materials have been widely used for visual inspection, rewriting papers, humidity sensors, and the paint and coating industry. However, the investigation on hydrochromic coordination polymers is relatively rare. In this work, a hydrochromic coordination polymer [Ni(L1)(L2)(H2O)(DMF)]·DMF (1) (L1 = N,N'-di(4-pyridyl)-1,4,5,8-naphthalene diimide, H2L2 = 4,4′-stilbenedicarboxylic acid, and DMF = N,N'-dimethylformamide) is synthesized by employing the π-electron-deficient L1 as the main ligand under the solvothermal condition. Compound 1 displays a rare inclined 2D → 3D polycatenation framework, resulting in extraordinary flexibility and stability that enables compound 1 to undergo cell compression or expansion after water loss or absorption, thereby altering the distance between the electron donor and the acceptor, causing the generation or quenching of radicals and hydrochromic phenomenon. Compound 1 undergoes a color change from yellow to green upon heating at 150 °C within five minutes or placing in a desiccator with concentrated sulfuric acid as desiccant for several hours. The green samples can be restored to yellow after being placed in the air for about two minutes. If the green samples contact with water directly, they can immediately return to yellow. The hydrochromic mechanism is investigated by thermogravimetric analysis, UV–Vis, infrared spectra, electron paramagnetic resonance spectra, powder X-ray diffraction spectra and density functional theory simulation.

Contrasting Networks and Entanglements in Uranyl Ion Complexes with Adipic and trans,trans-Muconic Acids.

Adipic (hexane-1,6-dicarboxylic, adpH2) and trans,trans-muconic (trans,trans-hexa-2,4-diene-1,6-dicarboxylic, mucH2) acids have been reacted with uranyl cations under solvo-hydrothermal conditions, yielding nine homo- or heterometallic complexes displaying in their crystal structure the effects of the different flexibility of the ligands. The complexes [PPh4]2[(UO2)2(adp)3] (1) and [Ni(bipy)3][(UO2)2(muc)3]·5H2O (2), where bipy is 2,2'-bipyridine, crystallize as diperiodic networks with the hcb topology, the layers being strongly puckered or quasiplanar, respectively. Whereas [(UO2)2(adp)3Ni(cyclam)]·2H2O (3), where cyclam is 1,4,8,11-tetraazacyclotetradecane, crystallizes as a diperiodic network, [(UO2)2(muc)3Ni(cyclam)]·2H2O (4) is a triperiodic framework in which the NiII cations are introduced as pillars within a uranyl-muc2- framework with the mog topology. [UO2(adp)(HCOO)2Cu(R,S-Me6cyclam)]·2H2O (5), where R,S-Me6cyclam is 7(R),14(S)-5,5,7,12,12,14-hexamethylcyclam, is a diperiodic assembly with the sql topology, and it crystallizes together with [H2NMe2]2[(UO2)2(adp)3] (6), a highly corrugated hcb network with a square-wave profile, which displays 3-fold parallel interpenetration. In contrast, [(UO2)3(muc)2(O)2Cu(R,S-Me6cyclam)] (7) is a diperiodic assembly containing hexanuclear, μ3-oxido-bridged secondary building units which are the nodes of a network with the hxl topology. The two related complexes [PPh3Me]2[(UO2)2(adp)3]·4H2O (8) and [PPh3Me]2[(UO2)2(muc)3]·H2O (9) crystallize as hcb networks, but their different shapes, undulated or quasiplanar, respectively, result in different entanglements, 2-fold parallel interpenetration in 8 and 2-fold inclined 2D → 3D polycatenation in 9.

Three Co(II)-containing coordination polymers displaying solvent determined entanglement structures and different ammonia and amines selective sensing properties

Nowadays it is necessary to develop selective sensing materials of ammonia and amines because toxic ammonia and amines are widely distributed in the environment. In this work, π-electron-deficient N,N′-di(4-pyridyl)-1,4,5,8-naphthalene diimide ligand was used to construct coordination polymers with selective sensing behaviors towards electron-rich ammonia and amines vapors. Three coordination polymers 1–3 with solvents dependent entanglement structures have been successfully synthesized. Compounds 1 and 3 display similar 2D + 2D → 3D polycatenation architectures, but they have pores with different sizes that can accommodate different lattice solvent molecules. Compound 2 exhibits a 3D 2-fold interpenetrating framework with a 6-connected pcu net. Compounds 1 and 3 can selectively sense ammonia and amines vapors in solid state through visual color changes with different response time.

Reversible Water Ad-/Desorption Behavior of a 3D Polycatenation Network, [Zn(bpp)(BDC)]·1.5(H2O), Constructed by 2D Undulated Layered MOF

A three-dimensional (3D) polycatenation supramolecular network with chemical formulas, [Zn(bpp)(BDC)]·1.5H2O (1), (bpp = 1,3-bis(4-pyridyl)propane, BDC2− = dianion of terephthalic acid), was synthesized and structurally determined. In compound 1, the coordination geometry of Zn(II) ion is distorted tetrahedral, where its 2D undulated layered framework is constructed via the bridges of Zn(II) ions with bpp and BDC2− ligands. Adjacent 2D layers are arranged in a combined parallel and interpenetrated manner to complete its 3D polycatenation supramolecular architecture. Compound 1 shows a one-step dehydration process with the weight losses of 6.1%, approximately equal to the weight percentage of losing 1.5 guest water molecules. The cyclic thermogravimetric analysis reveals that compound 1 shows reversible, sponge-like water de-/adsorption behavior during de-/rehydration processes. Compound 1 also exhibits significant water vapor hysteresis isotherm.

Cu(II) MOFs Based on Bipyridyls: Topology, Magnetism, and Exploring Sensing Ability toward Multiple Nitroaromatic Explosives.

In this work, a series of three copper(II) metal-organic frameworks (MOFs), [Cu(4,4′-DP)Cl]n (1), [Cu(4,4′-DP)0.5Cl]n (2), and [Cu(4,4′-TMDP)Cl]n (3) (4,4′-DP = 4,4′-dipyridyl, 4,4′-TMDP = 4,4′-trimethylenedipyridyl), is designed and synthesized under solvothermal conditions. Crystallographic investigations reveal that 1 and 2 have tetrahedral and 3 has octahedral environment around the Cu(II) ion. By varying the solvent conditions and ligand derivatives, the topology can be interestingly tuned. TOPOS Pro provides topological conclusions that 1 is stabilized by unusual 2D + 2D → 3D polycatenation of layers lying in (110) and (11̅0) planes with dihedral angle of 90° showing altogether fes, hcb, and sql topologies. On the other hand, 2 exhibits a bey (3,4-c net) topology and 3 shows 4-fold interpenetration with the dia topology. The dc measurements for 1–3 performed on polycrystalline samples in a 0.1 T field confirm strong ferromagnetic behaviors for 1 and 2 and moderate antiferromagnetic behavior for 3. To examine the sensing properties of the three MOFs, various hazardous nitroaromatic compounds (NACs) were used as analytes. While 1 is a potent fluorescence sensor for highly sensitive detection of multiple NACs, 2 selectively detects meta-dinitrobenzene (m-DNB) with KSV = 5.73 × 105 M–1 and a remarkably lower limit of detection (LOD) value of 1.23 × 10–7 M. 3 does not show sensing ability toward any NAC probably due to the coordination environment being different from those in 1 and 2. The work demonstrates fine-tuning of the topology and in turn magnetic and sensing properties by changing the reaction conditions.

Syntheses, Crystal Structures, and Fluorescence Properties of Two 2D→2D Coordination Polymers Based on the Flexible 4-Substituted Bis(1,2,4-triazole) Ligand

Two new 2D → 2D zinc(II) coordination polymers, [Zn(btre)0.5(nbdc)(H2O)]n (1) and {[Zn(btre)0.5(MeOip)(H2O)2]·H2O}n (2) (btre = 1,2-bis(1,2,4-triazol-4-yl)ethane, nbdc=3-nitro-1, 2-benzenedicarboxylate, MeOip=4-methoxybenzene-1, 3-dicarboxylate) were synthesized at room temperature condition and characterized by IR spectra, elemental analyses, single-crystal and powder X-ray diffractions. Three sets of equivalent 2D (6, 3) networks parallel polycatenated with each other to give a 2D → 2D network in 1 and 2. There are strong π-π interactions and hydrogen bonding interactions between adjacent parallel polycatenated 2D (6, 3) network in 1. Only hydrogen bonding interactions exist in 2. Thermal stabilities and luminescence of 1 and 2 were investigated.

Three novel polyoxometalate-based inorganic-organic hybrid materials based on 2,6-bis(1,2,4-triazol-1-yl)pyridine.

Three novel inorganic–organic hybrid materials [Co(btp)2(W5O16)(H2O)]n (1), [Cd3(btp)6(PW12O40)2(H2O)6·6H2O]n (2), and [Ag3(btp)2(PMo12O40)·1.5H2O]n (3) (btp = 2,6-bis(1,2,4-triazol-1-yl)pyridine) have been hydrothermally synthesized and characterized by IR spectroscopy, single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), elemental analysis and thermal gravimetric analysis (TGA). The most striking structure feature of compound 1 is a 3D polycatenation framework, interpenetrated by a 2D 4-connected sql topology layer and a 3D 6-connected rob topology framework. Compound 2 exhibits a rare meso-helices 3D network with different chiralities crossing coexistence. Compound 3 also holds a 3D framework formed by linking terminal oxygen atoms of [α-PMo12O40]3− anions and silver ions in a 2D metal–organic layer. Compound 1 displays antiferromagnetic behavior. The luminescence, electrochemical and photocatalytic properties of compounds 1–3 have also been investigated. Compound 3 exhibits significant electrochemical activity for the reduction of H2O2 while compounds 1 and 2 show efficient photocatalytic activities for the degradation of Rhodamine B (RhB). Furthermore, the three compounds display luminescence behaviors in the solid state.

Designed Cluster Assembly of Multidimensional Titanium Coordination Polymers: Syntheses, Crystal Structure and Properties.

The exploitation of new titanium-based coordination polymers (Ti CPs) with high crystallinity is difficult but highly desirable for their potential applications in photocatalysis. Herein, a cluster-cooperative assemble strategy is developed to synthesize Ti CPs. By utilizing various bifunctional ligands containing carboxylate acids and N-donor groups, we successfully assembled the zero-dimensional (0D) [(Ti3 O)(iPrO)8 ]2+ or [(Ti4 O2 )(iPrO)6 ]6+ clusters into one-dimensional (1D) tube-, ribbon-, or helical chain-shape architectures, two-dimensional (2D) layered structures, and a rare parallel 2D→three-dimensional (3D) polycatenation framework with various copper iodide dopants, including rhombus- or wing-shaped Cu2 I2 and tetrahedron- or ladder-shaped Cu4 I4 . The as-synthesized compounds display strong absorption in the visible region with narrow band gaps ranging from 1.70 to 2.72 eV and exhibit good photocatalytic activities in the degradation of organic pollutants.

A microporous metal-organic framework with unusual 2D → 3D polycatenation for selective sorption of CO2 over CH4 at room temperature

By appealing to the pillared-layer strategy, a new Zn(II)-based microporous polycatenated metal-organic framework {[Zn2(bpydb)2(EtOH)(4-bpdb)](DMF)4(EtOH)2}n (1, bpydb = 4,4′-(4,4′-bipyridine-2,6-diyl)dibenzoate, 4-bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, DMF = N,N-dimethylformamide) with Lewis basic sites on the pore surface has been designed and generated by the solvothermal reaction of mixed ligands (bpydbH2 and 4-bpdb) and Zn(NO3)2 · 6H2O. The structure of 1 displays a 3D pillared-bilayer network generated from polycatenation of the 2D bilayers with an accessible solvent void of 43%. Its porosity has been verified by the N2 sorption at 77 K, which reveals a BET surface of 545 m2/g and pore volume of 0.324 cm3/g. Moreover, compound 1 shows excellent adsorption selectivity for CO2 over CH4 around room temperature, which has been correlated to the specific interaction of CO2 with functional azine groups that decorated the pore channels.

Structural diversity of three entangled metal-organic frameworks from a bisimidazole ligand and dicarboxylic acids with varied length

Based on a bisimidazole ligand and dicarboxylic acids with varied length, three entangled metal-organic frameworks have been synthesized and structurally characterized. Compound 1 shows a 4-fold interpenetration of dia net. Compound 2 presents an unusual 1D→3D polycatenane by the 4-fold interpenetration of 1D tubular net. Compound 3 exhibits a 3-fold interpenetration of pcu net. Their luminescent properties were also investigated.

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.

An unprecedented self-penetrating Cu(I)-MOF based on a new 1Dmeso-ladder + 2Dmeso-layer → 3D polycatenation subnet showing luminescent sensing for nitrobenzene

An unprecedented self-penetrating Cu(I)-MOF was synthesized. Interestingly, Complex 1 exhibits a novel two-level hierarchical entangled system with a new (73)(66.74)(66.73.8) topology first constructed from the rare meso-helical ladder and layer via inclined polycatenation, and also shows strong green emission in the solid-state and highly luminescent sensing for nitrobenzene.

Employing mixed-ligand strategy to construct a series of luminescent Cd(ii) compounds with structural diversities

Eight new cadmium compounds, namely, {Cd2(ox)2(bib)1.5}n (1), {Cd(mal)(bib)0.5}n (2), {Cd(fum)(bib)(H2O)}n (3), {Cd2(suc)(bib)(NO3)2(H2O)}n (4), {Cd2(glu)2(bib)}n (5), {Cd(adp)(bib)}n (6), {[Cd(sub)(bib)]·(H2O)3}n (7) and {[Cd(aze)(bib)1.5]·(H2O)5}n (8) (bib=1,4-bis(N-imidazolyl)butane, H2ox = oxalic acid, H2mal = malonic acid, H2fum = fumaric acid, H2suc = succinic acid, H2glu = glutaric acid, H2adp = adipic acid, H2sub = suberic acid, and H2aze = azelaic acid) were constructed from flexible bis(imidazole) ligands incorporating a variety of aliphatic dicarboxylic acids. They were characterized using elemental analysis, IR, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. Compound 1 exhibits a 3D self-penetrating framework with a novel {44·54·62·74·8}{53·62·7}2 topology that can interestingly be regarded as a cross-link of two interpenetrating pcu networks. Compound 2 displays a six-connected self-penetrating pillared-layer framework with a roa topology. The structure of 3 is an unprecedented 2D → 3D polycatenation based on a (42·64) bilayer. If hydrogen bonding interactions are taken into account, the resulting structure displays a 3-fold interpenetrated 3D rob network. Compound 4 is comprised of 2D (4,4) networks, and the adjacent sheets are extended into a 3D interdigitated framework via hydrogen-bonding interactions. Compounds 5 and 6 are based upon 3D pillared-layer frameworks constructed from [Cd(glu)]n/[Cd(adp)]n layers and the bib pillars. Both 7 and 8 are 3D frameworks with the same dia topology except that the former shows an abnormal 4-fold [2 + 2] interpenetrating mode and the latter is a single dia network without interpenetration. A comparison of compounds 1–8 demonstrates that the structure diversities may be greatly induced by increasing the spacer lengths and coordination modes of aliphatic dicarboxylic acids. Moreover, the photoluminescent properties of 1–8 are also discussed.

Syntheses, structures, luminescent and gas adsorption properties of five new interpenetrated, 2D and 3D metal–organic frameworks based on a semi-rigid bis(imidazole)-carbazole ligand

We have succeeded in constructing five metal–organic frameworks, [Zn(L)SO4] (1), [Zn(L)(bdc)]·H2O (2), [Zn(L)(abdc)]·0.5H2O (3), [Zn(L)(oba)]·2H2O (4) and [Zn(L)2(suc)2] (5), based on a semi-rigid bis(imidazole)-carbazole ligand [9-ethyl-3,6-di(1H-imidazol-1-yl)-9H-carbazole (L)] and five rigid/flexible dicarboxylic acids (DPac=2,6-pyridine dicarboxylic acid, H2bdc=p-phthalic acid, H2abdc=azobenzen-4,4′-dicarboxylate, H2oba=4,4-oxybisbenzoic acid and H2suc=succinic acid). Complexes 1–5 were characterized by single crystal X-ray diffraction, elemental analysis, power X-ray diffraction (PXRD), IR spectroscopy and thermogravimetry. Complex 1 possesses a two-dimensional (2D) network which is constructed not by the co-ligand acid but by a sulfate anion. Both complexes 2 and 3 are two-dimensional (2D) sheet structures with 2D→3D polycatenation frameworks. Coordination polymer 2 contains interconnected 70-membered macrocycles and 3 forms a double helix-like 4-fold interpenetrated network. Complex 5 exhibits a three-dimensional (3D) sra network. The luminescent properties of 1–5 in the solid state and gas adsorption properties of 3 and 5 were also investigated.

Auxiliary Ligand-Assisted Structural Variation of Cd(II) Metal–Organic Frameworks Showing 2D → 3D Polycatenation and Interpenetration: Synthesis, Structure, Luminescence Properties, and Selective Sensing of Trinitrophenol

Four new metal–organic frameworks (MOFs) of Cd(II) ion, [Cd(fdc)(bipy)1.5](1), [{Cd(fdc)(bpee)1.5}.3(H2O)](2), [Cd(fdc)(3bpdb)(H2O)](3), and [{Cd2(fdc)2(4bpdb)3}.1.5(4bpdb).2(H2O)](4) (where, fdc = 2,5-furandicarboxylate dianion, bipy = 4,4′-bipyridine, bpee = 1,2-bis(4-pyridyl)ethylene, 3bpdb = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene, and 4bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene) have been successfully synthesized using mixed ligand systems and characterized by single crystal X-ray analysis and other physicochemical studies. Structural determination revealed that compounds 1 and 4 possess a rare 2D → 3D polycatenated pillared-bilayer structure with {48.62} SP 2-periodic net topology. Compound 2 has a novel threefold interpenetrating 3D hexagonal framework structure with {46.64} sqc-net topology, whereas compound 3 features a 2D Zig-Zag network with {44.62} sql-net topology. Interestingly, compounds 1 and 4 are the first examples of Cd(II) MOFs based on fdc ligand and bipy/4bpdb spacers exhib...

Influence of the Different Dicarboxylate Ligands on The Topological Net of Manganese(II) Coordination Polymers: Syntheses, Crystal Structures. and Luminescent Properties

AbstractThe self‐assembly of MnII ions and 1,4‐bis(2‐methyl‐imidazole‐1‐yl)benzene (bip) with two different dicarboxylate ligands, benzophenone‐4,4′‐dicarboxylic acid (H2bda) and 1,4‐naphthalenedicarboxylic acid (H2nda) via hydrothermal synthesis resulted in two interesting coordination polymers, [Mn(bda)(bip)]n (1) and [(Mn(nda)(bip)0.5(H2O)]n (2). Their structures were determined by single‐crystal X‐ray diffraction and elemental analyses, as well as IR spectroscopy. Complex 1 exhibits an unusual polycatenated 2D+2D→3D framework. Complex 2 shows a twofold interpenetrated pcu net. In addition, the solid‐state photoluminescent properties of 1 and 2 were investigated at room temperature.

A series of entangled coordination polymers assembled by a V-shaped bisimidazole ligand and various dicarboxylic acids: synthesis, characterization and luminescence properties

Based on a V-shaped bisimidazole ligand and various dicarboxylic acids, nine entangled coordination polymers, namely, [Zn(o-bdc)(bips)]·2H2O (1), [Zn2(cdc)2(bips)2]·2H2O (2), [Zn2(bpedc)2(bips)2] (3), [Zn(odc)(bips)]·H2O (4), [Zn2(sdc)2(bips)2]·5H2O (5), [Co2(sdc)2(bips)2(H2O)]·2H2O (6), [Cd2(bpdc)2(bips)2]·3H2O (7), [Cd2(2,6-ndc)2(bips)2(H2O)2]·2H2O (8) and [Cd(1,4-ndc)(bips)]·DMF·H2O (9) (bips = bis(4-imidazol-ylphenyl)sulfone, o-H2bdc = o-phenyldicarboxylic acid, H2cdc = 1,4-cyclohexanedicarboxylic acid, H2bpedc = 4,4′-stibenedicarboxylic acid, H2odc = 4,4′-oxybisbenzoic acid, H2sdc = 4,4′-sulfonyldibenzoic acid, H2bpdc = biphenyl-4,4′-dicarboxylic acid, 1,4-H2ndc = naphthalene-1,4-dicarboxylic acid, 2,6-H2ndc = naphthalene-1,4-dicarboxylic acid), have been synthesized and structurally characterized. Compound 1 exhibits a 2D → 2D polycatenane of 3-fold interpenetrated sql layers. Compound 2 shows a 2D → 3D polycatenane of 3-fold interpenetrated sql layers. Compound 3 displays a 2D → 3D polycatenane of 5-fold interpenetrated sql layers. Compound 4 exhibits a 2-fold interpenetration of CdSO4 networks. Compound 5 presents a 2D → 3D polycatenane by three-fold interpenetrated {42·63·8}2 layers. Compound 6 features an unusual 2D → 2D polycatenane framework assembled by the entanglement of sql layers containing 2-membered loops. Compound 7 exhibits a 1D → 3D polycatenane by the 3-fold interpenetration of 3-connected ribbons. Compound 8 displays a 3-fold interpenetration of SrAl2 networks. Compound 9 exhibits a 4-fold interpenetration of dia networks in a [2 + 2] mode. Their luminescence properties were also measured.

Construction of Zn(ii) and Cd(ii) metal–organic frameworks of diimidazole and dicarboxylate mixed ligands for the catalytic photodegradation of rhodamine B in water

A set of four metal–organic frameworks, namely, [Zn(1,3-BDC)(bmimb)]n (1), [Zn(1,4-BDC)(bmimb)]n (2), [Cd(1,3-BDC)(bmimb)]n (3), and [Cd(1,4-BDC)(bmimb)]n (4), have been prepared under solvothermal conditions (1,3-BDC = 1,3-benzenedicarboxylate; 1,4-BDC = 1,4-benzenedicarboxylate; bmimb = 4,4′-bis(4-methyl-1-imidazolyl)biphenyl). The long bmimb ligand (N⋯N separation of ca. 14.1 A) induces interpenetration of 1, 2 and 4 to increase both the framework stability and the density of effective catalytic metal centers. Compounds 1, 2 and 4 are interpenetrated 3D structures while 3 features a 2D structure. Compound 1 exhibits a parallel 2D → 3D polycatenation while 2 and 4 are isomorphous and feature 3D → 3D interpenetration. Compounds 1–4 fluoresce in the range of 350–372 nm in the solid state, whereas compounds 2 and 3 catalyze the almost complete photodegradation of rhodamine B (RhB) in water within ca. 4 h and can be recycled at least five times without loss in their crystallinity.