Search

This review mainly summarizes the recent progress of MOFs composed of N-heterocyclic carboxylate ligands in gas sorption/separation. This work may help to understand the relationship between the structures of MOFs and gas sorption/separation.

Two new three-dimensional (3D) metal–organic frameworks (MOFs), namely {[Cu2(L)(4,4′-bipy)(OH)]·H2O}n (1) and {[Mn3(L)2(4,4′-bipy)(DMA)2]·H2O}n (2), were constructed by a newly synthesized thioether carboxylic acid ligand 5-((formic acid-3-sulfur)methyl)isophthalic acid (H3L) and 4,4′-bipyridine (4,4′-bipy). Thioether bonds in H3L can rotate freely in space, which are conducive in constructing MOFs with rich and stable structures. Simultaneously, the uncoordinated sulfur atoms affect the polarity of the framework and play an important role in adsorption. Gas adsorption results indicated that 1 can selectively adsorb CO2 from the mixture of CH4/CO2. Moreover, due to the high catalytic activity of [Cu4(COO)6N4O2] clusters, 1 is also an excellent recyclable catalyst that can chemically fix CO2 into cyclic carbonate under mild solvent-free conditions. Therefore, 1 may be explored as a dual-functional material for industrial adsorption and catalysis.

A new multi-functional metal–organic framework, {[Cu2(HL)(H2O)2]·NMP·2H2O}n (1), was assembled by employing an asymmetrical V-shaped rigid multicarboxylic acid ligand H5L (H5L = 2,4-di(2′,5′-dicarboxylphenyl)benzoic acid) with Cu(II) ions. 1 possesses a 3D pore formed by two types of intersecting 1D cuboid channels. Moreover, owing to the abundant uncoordinated carboxylate O atoms decorated in the channels and open metal centers generated by the removal of coordinated water molecules, 1 exhibits a high CO2 adsorption capacity and significantly selective capture for CO2 over CH4. Hence, further research on the chemical fixation of CO2 is implemented, which reveals excellent heterogeneous catalytic activity. In addition, 1 displays particularly selective sorption towards the rhodamine B (RB) dye. Consequently, this study may provide a facile synthetic route for the construction of multi-functional materials.

Herein, we report a new 3D porous Co(II)-based metal–organic framework catalyst (Me2NH2)2[Co3(L)2(H2O)2]·2DMF (MOF I), which has been successfully prepared by using Co(II) ions and rigid V-shaped 3,5-di(2,4-dicarboxylphenyl)pyridine (H4L) via the solvothermal reaction. Structural analysis reveals that I displays a porous structure with the pore size of 16.2 × 7.2 A2 based on the trinuclear [Co3(COO)4(H2O)2N2] secondary building units (SBUs). Gas sorption experiments on the guest free sample I′ reveals a high capacity and selectivity to CO2 over CH4. And further, the catalytic explorations of the I′-catalyzed system (I′: 3 mol%; proline: 40 mol%; CH3CN: 2 mL) reveal that benzyl alcohols with different structures can be efficiently transformed into benzyl alcohols without by-products under mild conditions.

Suitable chemical components in water systems for human health are a crucial prerequisite for mankind's survival. Simple and effective innovations are being developed to efficiently monitor healthy and toxic substances. Here, with a hydrothermal technique, a novel thermostable metal–organic framework (MOF) [Cd2(L)(bib)0.5(H2O)3]n·1.75n(H2O) (MOF-1, H4L = biphenyl-2,3,3′,5′-tetracarboxylic acid, bib = 1,4-bis(imidazolyl)butane) was designed and synthesized. MOF-1 shows a 4,5-connection binodal 3D fsx-type topological net with irregular cages, which the bulk materials show high phase purity, excellent thermo/aqua-stability and intense fluorescence. The luminescent MOF was studied for the highly sensitive detection of trace amounts of Fe3+ ions and nitrobenzene and shows high KSV values of 4.653 × 104 and 5.724 × 104, respectively. It was also demonstrated that MOF-1 possesses superior probing ability towards nine other nitroaromatic explosives with remarkable quenching percentages. These results offer a new possibility for the potential multiple recognition of various chemical substances in human body and water systems by utilizing novel dual-functionalized luminescent MOF sensors.

A novel two-dimensional coordination polymer with a negatively charged framework named {[(CH3)2NH2][Zn2(L)2]·DMF}n (1) was solvothermally synthesized via the assembly of Zn(II) ions with the organic ligand H3L (2-(3,5-dicarboxylphenyl)-6-carboxyl-benzimidazole). 1 was characterized by IR spectroscopy, thermogravimetry, single-crystal, and powder X-ray diffraction methods. 1 possesses a 1D rectangle channel decorated by abundant uncoordinated imidazole N atoms and carboxylate O atoms, and is a better CO2 adsorbent and promising CO2/CH4 selective material, suggesting potential application in gas separation. Moreover, 1 can also serve as a multi-responsive sensing material for detecting nitrobenzene (NB) and Cr2O72−via a luminescence quenching effect with a low detection limit, and the mechanisms of the quenching effect and sensing properties of 1 are discussed in detail.

A new 3D luminescent Ba-organic framework {[Ba3L2(NMP)2(H2O)2]·2NMP·H2O}n (1) was first synthesized based on Ba(II) and a triangular-shaped bridging rigid ligand, namely 1,3,5-tris(4-carboxyphenly)benzene (H3L), via solvothermal reaction (NMP = N-methyl pyrrolidone), thereby forming a stabilized network including a one-dimensional (1D) infinite rod-like helical metal chain. 1 may be explored as a recyclable heterogeneous catalyst for the efficient fixation of CO2 to form serviceable cyclic carbonate since 1D channels remain decorated with abundant open metal sites (OMSs), and the catalytic efficiency of 1 was up to 98% for 1-bromo-2,3-propylene oxide. Simultaneously, the luminescence sensing shows that 1 has excellent response and sensitivity towards pollutants such as Fe3+, Cr2O72−, CrO42−, and [Fe(CN)6]3− ions. Moreover, 1 exhibits the particularly selective sorption towards the Congo red (CR) dye. Consequently, this study may provide a facile synthetic route for the construction of multi-functional Ba-MOF materials.

Three isostructural lanthanide metal–organic frameworks (Ln-MOFs), {[Ln(L)(H2O)2]·H2O}n (M-Ln, Ln = Eu/Tb/Dy), were prepared with a flexible 3,5-(4-carboxybenzyloxy) benzoic acid (H3L) ligand and lanthanide ions by a solvothermal method. M-Ln are two-dimensional (2D) grid layer-stacking frameworks. M-Eu exhibits excellent chemical stabilities against organic solvents and shows strong luminescence. The experimental results indicated that M-Eu could be used as an ideal fluorescent probe to detect nitrobenzene (NB) in different solvents with a lower detection limit. M-Eu can also be used as a pH sensor because of its superior water stability. Furthermore, M-Eu and M-Tb show unique strong luminescence properties with high absolute quantum yields. The quantum yields can even reach up to 11.8% and 60.5%, respectively. Simultaneously, various kinds of heterometallic doped M-EuxTb1−x MOFs were acquired by tuning the ratios of Eu3+/Tb3+ ions, showing the unique color changes from red, orange-red, orange, orange-yellow, light yellow, yellow to green.

Single-crystal-to-single-crystal (SCSC) transformation has been demonstrated to provide an ideal platform to explore the formation process of chemical bonds, which is conducive to making function-oriented crystal synthesis a reality. A solvent as a ligand or a structure-directing agent plays a significant role in the structural formation of coordination polymers (CPs), and its removal/adsorption or exchange can affect the change in metal coordination environments. In this article, we provide a brief overview of recent progress in the effect of coordinated solvent molecules on metal coordination environments of CPs in SCSC transformations. We highlight three different categories based on their stimuli conditions, heat treatment, immersion in solvent or mother liquid, and exposure to vapor. We try to discuss the criteria for CPs in which the metal coordination spheres can be affected by the coordinated solvents, which may provide new insights into the rational design and construction of CPs with the desired structures and properties.

Herein, two new water-stable magnetic frameworks, [Cu1.5(L)(H2O)]·2H2O (1) and [Co4(L)2(CH3CN)(OH)2(H2O)4]·3H2O (2) (H3L = 5-((4-carboxypyridin-2-yl)oxy) isophthalic acid), were synthesized by a solvothermal method in similar reaction systems and characterized by infrared spectroscopy, powder X-ray diffraction and thermogravimetric measurements. Due to their different metal ions, 1 shows a trinodal (4,4,4)-connected three-dimensional (3D) framework that possesses 1D channels based on [Cu2(COO)4] paddle-wheel secondary building units (SBUs), whereas 2 is a 2D layered network based on tetranuclear [Co4(COO)6(μ3-OH)2] SBUs and reveals a (3,6)-connected kgd topological structure. The gas adsorption explorations demonstrated that 1 exhibited commendable selectivity for CO2 over CH4. Moreover, both 1 and 2 showed different degrees of antiferromagnetic exchange action.

A novel two-dimensional Cd-based metal–organic framework, {[Cd(Hcpnc)(DMF)]·DMF·2H2O}n (Cd-MOF) has been synthesized successfully under solvothermal conditions by utilizing a multifunctional N,O-building block ligand, 2-(2,5-dicarboxylphenyl)nicotinic acid (H3cpnc), which is a new and virtually unexplored multifunctional pyridine-tricarboxylic building block. The product was isolated as a stable crystalline solid and was fully characterized by IR spectroscopy, elemental analyses, thermogravimetry and differential scanning calorimetry, powder X-ray diffraction, single-crystal X-ray diffraction analyses, and X-ray photoelectron spectroscopy. The solid-state luminescence properties of the Cd-MOF were studied at ambient temperature. The compound shows high selectivity and sensitivity for Cu2+ ions and nitrobenzene by the luminescence quenching behavior with excellent repeatability. Additionally, the Cd-MOF exhibits an excellent specific capacitance of 321 F g−1 at 0.5 A g−1 and it still retains 95.2% of the original capacitance after 1000 cycles. Therefore, the Cd-MOF as a kind of bifunctional material will have broad application prospects in luminescence detection and supercapacitors.

Herein, three new luminescent metal–organic frameworks (MOFs), namely {[Cd4(H3L)4(H2O)12]·2.5H2O}n (1), {[Cd(L)]·2.5H2O·3[H2N(Me)2]}n (2), and {[Cd2(L)(DMA)]·[H2N(Me)2]}n (3), were designed and successfully prepared via a solvothermal reaction using V-shaped rigid multicarboxylate 2,4-di(3′,5′-dicarboxylphenyl)benzoic acid (H5L) and Cd(II) salts in various solvent systems. The structural analyses indicated that the H3L2−/L5− ligands took three different coordination fashions in 1–3; this resulted in a diversity of targeted MOFs. The solid-state luminescence properties of three MOFs were studied under ultraviolet light irradiation at ambient temperature, and 3 showed a high selectivity and sensitivity for nitrobenzene and Fe3+ because of the quenching effect. Thus, it could be a potential crystalline material for detecting these substances. The mechanisms of the quenching effect and sensing properties of 3 have been discussed in detail.

Five coordination polymers, {[Co3(L)2(H2O)2]·4H2O} (1), {[Cd3(L)2(NMP)2]} (2), {[Cu(HL)]·NMP} (3), {[Cd(HL)(2,2′-bipy)]} (4) and {[Co(HL)(4,4′-bipy)(H2O)2]} (5) with different dimensional structures, have been solvothermally synthesized from a trifunctional N,O-building block, 5-(3,4-dicarboxylphenoxy)nicotinic acid (H3L) that combines three distinct types of functional groups (COOH, N-pyridyl, and O-ether), and an auxiliary co-ligand, 2,2′-bipy or 4,4′-bipy (2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine). H3L contains three different types of functionalities and has eight potential coordination sites, which results in diverse coordination patterns and different dimensionalities depending on the reaction conditions. Complexes 1–3 display 2D layer structures with 1D channels, 4 shows a 2D + 2D → 2D interpenetrated wavy structure, while 5 exhibits a 1D chain structure. 1 demonstrates an effective storage capacity for CO2 as well as high selectivity for CO2 over CH4 under ambient conditions. The magnetic properties revealed antiferromagnetic behaviors for complexes 1, 3 and 5. Also, the alternating-current susceptibility of 5 displays slow magnetic relaxation, showing interesting magnetic behavior with an effective energy barrier of 8.98 K.

Five coordination polymers, {[Zn(dtp)]·H2O} (1), {[Zn(dtp)]·2CH3OH·NMP} (2), {[Mn2(dtp)2(H2O)4]·12(H2O)} (3), {[Mn(Hdtp)(Cl)]} (4) and {[Mn(dtp)(H2O)]·1.5H2O} (5) with different dimensional structures, have been solvothermally synthesized by utilizing the H2dtp ligand (H2dtp = 4′-(3,-5-dicarboxyphenyl)-2,2′:6′,2′′-terpyridine). All complexes are characterized by single-crystal X-ray diffraction, elemental analysis, IR spectra, thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD). The Zn(II)-based complexes 1 and 2 display a 2D wavy layer structure and a 3D porous framework with a 1D channel, respectively. The three Mn(II)-based complexes 3–5 exhibit two 1D chain and one 2D layer structures, respectively. Complexes 1 and 2 reveal their luminescence properties, whereas complexes 3–5 display an antiferromagnetic exchange. Meanwhile, an unusual stepwise adsorption for CO2 was also observed in 2.

In this report, seven new luminescent metal–organic frameworks (LMOFs), [Zn(L)0.5(H2O)2]·H2O (1), [Zn(L)0.5(DMF)] (2), [Zn3(L)(μ3-OH)2(H2O)4] (3), [Zn2(L)(DMA)(H2O)]·5(H2O) (4), [Cd(L)]·2(H3O)·(H2O) (5), [Cd2(L)(H2O)3] (6), and [Pb(L)0.5(H2O)] (7) (H4L = [1,1′:4′,1′′-terphenyl]-2′,3,3′′,5′-tetracarboxylic acid; DMF = N,N-dimethylformamide; DMA = N,N-dimethylacetamide) have been solvothermally synthesized by using Zn(II), Cd(II), Pb(II) ions and H4L in different solvent systems, all of which have been routinely characterized by elemental analysis, FT-IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Single-crystal X-ray diffraction analyses show the different dimensionalities (1D, 2D or 3D) of complexes 1–7. Comparative structural studies of 1–7 reveal that the L4− ligands adopt different coordination morphologies: 1 (η1μ1χ1), 2 (η2μ2χ2), 3 (η2μ2χ2), 4 (η2μ2χ2; η1μ1χ1), 5 (η2μ1χ2), 6 (η2μ2χ2; η2μ2χ3), and 7 (η2μ2χ2; η2μ3χ4) with Zn(II) (74 pm), Cd(II) (97 pm) and Pb(II) (119 pm) in different solvent systems, which produce the complexes with different frameworks. Complex 1 displays a 1D dimeric chain. Complexes 2 and 5 present a 2D layer structure with a uninodal 4-connected sql net with a symbol of (44·62). Complexes 3, 6 and 7 have a 3D dense packing structure based on infinite 1D rod-like secondary building units (SBUs). Complex 3 is designated as a binodal (4, 6)-connected fry topological net with the point symbol (510·63·78)(54·62). The whole network of 6 can be simplified as a binodal (4, 8)-connected flu topological net with a point symbol of (412·612·84)(46)2. Complex 7 can be seen as a new binodal (5, 10)-connected topological net with the point symbol (410)2(428·616·8). Complex 4 shows a 3D framework based on a binuclear [Zn2(CO)3O3] SBU, which can be viewed as a uninodal 4-connected sra topological net with the point symbol (42·63·8). Further, the solid-state luminescence properties of the complexes were measured and studied intensively at room temperature.

Reaction-determined assemblies of 6,6′-dinitrobiphenyl-2,2′,4,4′-tetracarboxylic acid (H4nbtc), various N-donor ligands and transition metal ions produce ten complexes, namely, [Zn2(nbtc)(bpa)·H2O]n (1), [Zn2(nbtc)(bpe)·H2O]n (2), [Zn2(nbtc)(2,2′-dpy)]n (3), Zn(H3nbtc)(phen)2 (4), {(H3O)2[Cd3(nbtc)2(H2O)3]·5H2O}n (5), [Cd2(nbtc)(ndpy)·0.5H2O]n (6), [Ag2(H2nbtc)(bpp)]n (7), [Co2(nbtc)(phen)2(H2O)2]n (8), [Ni2(nbtc)(phen)2(H2O)2]n (9) and Co(H2nbtc)(phen)2·2H2O (10) (bpa = 1,2-bis(4-pyridyl)ethane, bpe = 1,2-di(4-pyridyl)ethylene, bpp = 1,3-bis(4-pyridyl)propane, 2,2′-dpy = 2,2′-dipyridyl, phen = 1,10-phenanthroline, ndpy = 2-pyridinamine). Isostructural 1 and 2 feature 3D “bilayered-pillared” frameworks constructed from Zn2(μ2-COO)2(μ1-COO)2-nbtc4− wave-bilayers and bpa/bpe pillars. Unlike 1 and 2, both 3 and 6 exhibit 3D “brick-wall” frameworks constructed from nbtc4− and various SBUs (0D Zn2(μ2-COO)3(μ1-COO)1 for 3, 1D [Cd2(μ2-COO)4]n for 6). However, 3D 5 can be viewed as a combination of 2D “brick-wall” layers and 1D [Cd3-nbtc] chains. Moreover, in comparison to neutral 3 and 6 with pensile and cosmetic terminal ligands, complex 5 without an N-donor ligand is particularly interesting, containing two hydronium ions to balance the anion unit [Cd3(nbtc)2(H2O)3]2− as well as three types of coordinated Cd(II) ions (6-, 7- and 8-). Unlike 3, complex 4 is mononuclear, despite the two complexes employing similar terminal ligands (2,2′-dpy for 3, phen for 4). In 2D layered Ag(I) 7, the 0D Ag4(μ2-COO)4 SBUs initially form Ag4(μ2-COO)4-H2nbtc2− chains before being bridged by bpp ligands. Isostructural Co(II) 8 and Ni(II) 9 exhibit 1D looped infinite chains. Structural comparisons indicate that the SBUs, the coordination modes of the H4nbtc ligand, the synthetic conditions and the nature of the N-donor ligands are crucial factors with respect to the structures of these compounds. Furthermore, the luminescence properties of 1–7 were investigated in the solid state at room temperature.

Structural transformation has aroused wide interest and has emerged as a promising approach for the design and synthesis of novel coordination polymers. In this work, we found interesting structural transformation phenomena triggered from a nickel coordination polymer (CP). Two temperature-dependent two-dimensional (2D) CPs, 1 and 2 were synthesized from hydrothermal reactions, while the other two CPs, 2D 3 and 3D 4 were the products of the in situ thermal decomposition of 1. Interestingly, 1 could undergo methanol-mediated transformation to afford 2 and 2 might convert to 1 under the condition of adding bipy in water. The multi-step conversions from 1 to 3 and 3 to 4 triggered by heat treatment in the solid state accompany the very rare dynamic response of a sequential release of coordinated water and partial organic ligands. More importantly, the mechanism of the transformation has also been studied in detail. Moreover, 3 could revert back to 1 quickly upon exposure to air, and this reversible process of dehydration–rehydration could be repeated at least ten times, which could highlight the application for their use in moisture sensors.

Seven complexes, namely, {[Co2[(R,S)-bpdado]2(CH3CN)2(H2O)2]·2H2O}n1, {Cu[(R,S)-bpdado](H2O)}n2, {[Cu2[(R,S)-bpdado]2(H2O)2]·H2O}n2′, {[Cu(R,S)-bpdado]·EtOH}n2′′, {Cu[(R,S)-bpdado](phen)}2 (phen = 1,10-phenanthroline) 3, {Cu[(R,S)-bpdado](phen)(H2O)}2·8H2O 4 and {Cu[(R,S)-bpdado](dpy)(H2O)}2·4H2O (dpy = 2,2′-pyridine) 5, have been obtained via solvothermal or layered diffusional reaction based on an axially chiral ligand, (R,S)-2,2′-bipyridyl-3,3′-dicarboxylic acid-1,1′-dioxide ((R,S)-H2bpdado). These complexes tend to form under thermodynamic control in the crystallization process of complexes. Among them, 2′ and 2′′ were reported and obtained along with the preparation of 2. Five new complexes, 1–5, are characterized by single-crystal X-ray diffraction, elemental analyses, X-ray powder diffraction, and IR and thermogravimetric analyses. Four different structural complexes, 2D achiral layers 1, 2 and 2′′ and 1D nanotubular structure 2′, are constructed by the M3[(R,S)-bpdado] tecton (M = Co(II) or Cu(II)) in different arrangement modes. When various N-donor ligands are used, different binuclear complexes, 3–5, are assembled by the Cu2[(R,S)-bpdado] tecton in the same arrangement mode. Apart from the arrangement modes of the tecton, some other elements are also discussed, which influence the final structures, such as the coordination modes and conformations of (R,S)-bpdado, the different metal ions, the reaction temperature, the N-donor ligand and the solvent system.

Seven new mixed–ligand coordination polymers, {[Co0.5(bib)0.5(tftpa)0.5]·0.5H2O}n (1), [Cd2(bib)(tftpa)2]n (2), [Ni0.5(bib)0.5(tftpa)0.5]n (3), {[Co0.5(tftpa)(H2O)]·0.5bib·EtOH}n (4), {[Cd0.5(tftpa)(H2O)]·0.5bib·EtOH}n (5), [Cd3(bib)3(tftpa)3(MeOH)3]n (6), and [Cd(bib)(tftpa)(MeOH)]n (7) (bib = 1,4-bis(2-methylimidazol-1-yl)butane, H2tftpa = tetrafluoroterephthalic acid) have been synthesized under different reaction conditions and characterized by elemental analysis, IR, PXRD, single crystal X-ray diffraction analysis and thermogravimetric analysis. Complex 1 exhibits an unusual [2 + 2] interpenetrating diamond framework belonging to class IIIa with the point symbol 66. Complex 2 reveals a (3,4)-connected 3D framework with a unique double-stranded helical chain based on Cd–O–Cd and Cd–(COO)–Cd. Complex 3 presents a 4-fold interpenetrating 3D diamond framework belonging to class Ia with the point symbol 66. Complexes 4 and 5 display a 3D supramolecular architecture built on 2D stacked layers through hydrogen bonding and π–π interactions. Complex 6 also shows a 3D 4-fold interpenetrating diamond framework belonging to class Ia with the point symbol 66. Complex 7 features a 2D + 2D → 2D parallel polycatenated framework with the point symbol 44·62. The structural diversity of complexes 1–7 illustrate that a subtle change can have a marked effect on the crystal architectures. Moreover, the magnetic properties of complexes 1, 3, and 4, and the solid-state photoluminescence results for complexes 2, and 5–7 were also studied.

Five new solvent-induced cadmium coordination architectures, {[Cd(bib)(5-Br-H2ip)]·EtOH}n (1), {[Cd0.5(bib)0.5(5-Br-H2ip)0.5]·3H2O}n (2), {[Cd2(bib)(5-Br-H2ip)2(MeOH)]}n (3), {[Cd(bib)0.5(5-Br-H2ip)(H2O)2]·H2O}n (4), and {[Cd(bib)0.5(5-Br-H2ip)(H2O)]}n (5), have been constructed from the same materials (1,4-bis(2-methyl-imidazol-1-yl)butane (bib), 5-bromoisophthalic acid (5-Br-H2ip) and Cd(Ac)2·2H2O) under different reaction solvents. As controlled by solvent systems, compound 1 shows a 3-fold interpenetrating 3D framework based on the left- and right-handed helical chains, while compound 2 reveals a 3-fold interpenetrating 3D network and each single net is based on the left-handed, right-handed and meso-helical chains. Compound 3 is a 3D framework that can be simplified as a 6-connected net with (48·62) topology. Both 4 and 5 display 3D supramolecular frameworks through weak aromatic π–π stacking interactions and hydrogen bonding interactions. However, the topologies of 4 and 5 are definitely different. Compound 4 presents a 3-connected net with (82·10) topology, while compound 5 reveals a 4-connected net with (42·63·8) topology. The effects of solvents on the crystal structures were discussed and thermogravimetric analysis and solid-state photoluminescence results for 1–5 were investigated.

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.

An investigation into 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (bpt) and cupric or cadmium complexes with a large variety of aliphatic α,ω-dicarboxylic acids HOOC-X-COOH (X = (CH2)n, n = 0–4 corresponding to oxalic acid (H2ox), malonic acid (H2mal), succinic acid (H2suc), glutaric acid (H2glu) and adipic acid (H2adi); CHCH, maleic acid (H2male) and fumaric acid (H2fum)) is performed. Ten novel metal–organic architectures, [Cu2(bpt)(ox)2]n·2.92nH2O (1), [Cu(bpt)(mal)(H2O)]n·2nH2O (2), [Cu(bpt)(glu)]n (3), [Cu(bpt)(adi)]n (4), [Cu2(bpt)2(fum)2]n·3nH2O (5), [Cd(bpt)(mal)(H2O)]n (6), [Cd(bpt)(suc)]n (7), [Cd(bpt)(glu)]n·nH2O (8), [Cd2(bpt)2(male)2]n·2nH2O (9), and [Cd(bpt)(fum)(H2O)]n·nH2O (10) were successfully synthesized through varying the organic acid linkers. The molecule 1 is a 3D pillared-layer framework with the open channels encapsulating infinite 1D water chains. Complex 2 shows the contorted 2D layer, which is extended to a 2-fold interpenetrated 3D supramolecular net by antidromic R24(8) hydrogen-bonding pattern. Compound 3 is a grid-like layer motif with the terminal bpt ligands as pendants. The MOFs 4 and 5 present two-fold interpenetrating primitive cubic (α-Po) coordination networks. Interestingly, discrete tetrameric water clusters exist in the micropores of the MOF 5. For the cadmium complex 6, six-coordinated metal centers link malonate and bpt to form interdigitated layers through edge-to-face π–π stacking interactions. Coordination polymer 7 can be considered as six-connected self-penetrated topological 3D network, in which the right- and left-handed helices are alternately arranged into a wavy Cd/succinate layer. Flexible glutarate with cadmium atoms produces a 1D ribbon, and is further linked by bpt ligands to produce the 2D double-layered motif 8. Incorporating with rigid butenedioic acid, the reaction of seven-coordinated cadmium and bpt leads to two distinct 2D (4,4) layered frameworks 9 and 10, with a one-dimensional Cd–O chain observed in the former framework. A systematic structural comparison of these ten complexes indicates that the final polymeric structures could be tuned through the introduction of the different backbone length and flexibility of the aliphatic dicarboxylates. In addition, host–guest chemistry of MOFs 1 and 5, and the luminescent properties of cadmium compounds were discussed.

Five new Mn(II) metal–organic coordination polymers, [Mn(tbip)(bipy)]n (1), {[Mn(tbip)(dpe)]·1.5H2O}n (2), [Mn(tbip)(bpa)]n (3), [Mn(mip)(bpa)]n (4) and {[Mn3(mip)2(Hmip)2(bpp)2(H2O)2]·2H2O}n (5), were prepared through hydrothermal reactions of Mn(II) acetate with H2tbip (H2tbip = 5-tert-butyl isophthalic acid) or H2mip (H2mip = 5-methylisophthalic acid) in the presence of different dipyridyl co-ligands (bipy = 4,4′-bipyridine, dpe = 1,2-bi(4-pyridyl)ethene, bpa = 1,2-bi(4-pyridyl)ethane and bpp = 1,3-di(4-pyridyl)propane). All these compounds were characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. The structures of 1 and 2 are constructed of [Mn2(tbip)2]n layers, which consist of alternate left- and right-handed helical chains, and further pillared by bipy or dpe ligands into a 3D porous framework. Interestingly, there are two different sizes of pores in 1 and 2. From the topology point of view, both complexes 1 and 2 exhibit the rare rob network based on the dimeric [Mn(COO)]2 subunits as the 6-connected nodes. The ribbon-like chains having 8- and 16-membered rings in 3 and 4 result from dimeric Mn(II) units bridged by H2tbip or H2mip ligands, which are connected by the flexible dpa into 2D open layers. Complex 5 contains rare isophthalato-bridged trimanganese clusters as building units, which are further linked by mip anions to form a one-dimensional ladder-like chain with less common unidentate coordinated bpp decorated as pendants. The thermal stabilities and X-ray powder diffraction studies indicate that the microporous framework of 2 can keep stable even after the loss of guest water molecules. In addition, dominant antiferromagnetic coupling was observed in compounds 1–3 and 5.

An unusual 1D ladder-like silver(I) complex has been synthesized and characterized. The polymer exhibits interesting plywood-like stacking arrays and a novel five-folded interpenetrated supramolecular network with [3 + 2] catenations.