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The coordination polymers of Cu(ii) and Zn(ii) have been synthesized. Simultaneously, the selective in situ Br–Cl exchange mechanism, structures, magnetic properties, and the fluorescence lifetimes of complexes 1–2 are discussed in detail.

To investigate the synergistic coordination ability of a polytorsional-amide ligand to construct new coordination polymers (CPs), N,N′-bis(4-methylpyridin-4-yl)-1,4-naphthalenediamide (L) was selected as the main ligand. Ni2+ and Cu2+ with electrochemical activity and different carboxylates [2-nitrobenzoic acid (2-HNBA), 4-nitrobenzoic acid (4-HNBA), p-toluic acid (HPTA), 1,2-benzenedicarboxylic acid (1,2-H2BDC), pimelic acid (H2PIM), 1,3-phenylenediacetic acid (H2PDA), o-methylsalicylic acid (HOMSA), propanedioic acid (H2PRO) and azelaic acid (H2AZE)] have been selected, and ten new CPs were obtained: [Ni(L)2(2-NBA)2] (1), [Ni(L)(4-NBA)2(H2O)2] (2), [Ni(L)(PTA)2(H2O)2] (3), [Ni(L)(1,2-BDC)(H2O)3]·H2O (4), [Ni(L)(PDA)]·0.5H2O (5), [Ni(L)(PIM)]·0.5H2O (6), [Cu(L)(4-NBA)2] (7), [Cu(L)(OMSA)2(H2O)] (8), [Cu(L)(PRO)(H2O)]·3H2O (9) and [Cu(L)(AZE)(H2O)] (10). The ten CPs were structurally determined through single-crystal X-ray diffraction analyses, PXRD and IR spectra. 1, 5, 6 and 10 are the 4-connected 2D networks. 2 and 3 are similar racemic chains. 4 and 7 are 1D helical structures. 8 is a zigzag chain and 9 is a “U” type chain. The effects of the twist degrees of the amide ligands and the coordination features of the carboxylates/metal ions on the structures and properties of the target CPs were investigated. 1–10 modified carbon paste electrodes (n-CPEs) display a quasi-reversible oxidation–reduction process at the surface of the n-CPE. Representative CPs (2, 5, 7 and 10) show good electrochemical sensing properties for ascorbic acid (AA) and chloramphenicol (CAP).

The designing and practicality of luminescent coordination polymers (LCPs) as sensors for the detection of molecules and ions constitutes an active area of research. Three new one-dimensional LCPs, [Zn2(4-bpft)2(1,3-BDC)2]·2H2O (LCP 1), [Zn(4-bpft)(5-MIP)] (LCP 2), and [Zn(4-bpft)(5-HIP)] (LCP 3) (4-bpft = N,N′-bis(4-pyridine formamide)-3,4-thiophene; 1,3-H2BDC = isophthalic acid; 5-H2MIP = 5-methylisophthalic acid; H2HIP = 5-hydroxyisophthalic acid), have been successfully synthesized with a new amide-thiophene-derived bis-pyridyl ligand under hydrothermal conditions. The LCPs 1–3 were characterized by single-crystal X-ray diffraction, FT-IR, and powder X-ray diffraction patterns, which show a 1D chain structure. A series of luminescence recognition tests proved that LCPs 1–3 can act as fluorescent sensors for detecting Hg(II) ions and purines in an aqueous environment. Besides, LCPs 1–3 possess good stability and can selectively detect Hg(II), adenine, and guanine in the presence of competing analytes. Consequently, LCPs 1–3 are highly promising candidates for sensing mercury ions, adenine, and guanine in water.

To study the effects of metal ions and various carboxylates on the assembly and structures of coordination polymers (CPs) based on a bis-pyridyl-bis-amide ligand [N,N′-bis(4-methylpyridine-4-yl)-2,6-naphthalene dicarboxylamide] (4-bmnpd), eight Zn(II) and Cd(II) CPs, namely [Cd(4-bmnpd)(2-NBA)2] (1), [Cd(4-bmnpd)(3-NIP)(H2O)] (2), [Cd2(4-bmnpd)(TCPA)2] (3), [Cd(4-bmnpd)(5-HIP)(H2O)] (4), [Cd(4-bmnpd)0.5(5-MIP)(H2O)] (5), [Cd3O(4-bmnpd)(1,4-PHDA)2(H2O)]·H2O (6), [Zn(4-bmnpd)(5-MIP)] (7) and [Zn(4-bmnpd)(1,2,4,5-BTA)0.5]·2H2O (8) [2-HNBA = 2-nitrobenzoic acid, 3-H2NIP = 3-nitrophthalic acid, H2TCPA = tetrachlorophthalic acid, 5-H2HIP = 5-hydroxyisophthalic acid, 5-H2MIP = 5-methylisophthalic acid, 1,4-H2PHDA= 1,4-phenylenediacetic acid and 1,2,4,5-H4BTA = 1,2,4,5-benzenetetracarboxylic acid] were synthesized under hydrothermal conditions. CPs 1–8 were characterized by elemental analysis, IR and powder X-ray diffraction. Both CPs 1 and 2 are 2D networks. CP 3 shows a 2D 3,4,5-coordinated net based on binuclear nodes. CPs 4 and 5 are 2D lamellar structures with (4,4) and (3,4) topologically connected patterns, respectively. CP 6 is a 3D framework constructed from multi-member [Cd10(1,4-PHDA)4]n rhombus rings and 1D [Cd3O2]n chains. CP 7 is a 1D ladder structure. CP 8 is a 2D structure extended by deprotonation of 1,2,4,5-H4BTA and 4-bmnpd linkers. The influence of the choice of metal as well as the carboxylic acid on the structures of the above CPs is discussed in detail. The fluorescence sensing properties of CPs 1–8 toward metal cations (Fe3+), anions (CrO42−, Cr2O72−) and antibiotics (oxytetracycline) were investigated. The limits of detection for Fe3+, CrO42−, Cr2O72− and oxytetracycline were 6.9 × 10−5–1.5 × 10−4, 6.9 × 10−5–1.3 × 10−4, 7.7 × 10−5–1.3 × 10−4, and 8.5 × 10−5–9.6 × 10−4, respectively.

In this work, six CoII coordination polymers (CPs) based on a new semi-rigid methylene-bridged bis-pyridyl-bis-amide ligand N,N′-bis(4-methylenepyridin-4-yl)-2,6-naphthalenedicarboxamide (4-bmpnd) and various polycarboxylates, namely [Co(4-bmpnd)(5-HMIP)2(H2O)2] (1), [Co2(4-bmpnd)2(5-NIP)2(H2O)]·2H2O (2), [Co2(4-bmpnd)(5-AIP)2(H2O)]·2H2O (3), [Co(4-bmpnd)0.5(1,4-CHDC)]·H2O (4), [Co(4-bmpnd)(1,4-NDC)(H2O)2]·2DMF (5), and [Co(4-bmpnd)(1,2,4,5-BTA)0.5(H2O)] (6) (5-H2MIP = 5-methylisophthalic acid, 5-H2NIP = 5-nitroisophthalic acid, 5-H2AIP = 5-aminoisophthalic acid, 1,4-H2CHDC = 1,4-cyclohexanedicarboxylic acid, 1,4-H2NDC = 1,4-naphthalenedicarboxylic acid, and H4BTA = 1,2,4,5-benzenetetracarboxylic acid) have been constructed by a hydrothermal/solvothermal method. Their structures are characterized by infrared spectroscopy, powder X-ray diffraction and single-crystal X-ray diffraction. CP 1 has a 1D linear structure. CP 2 displays a 2D 4-connected wave network. CP 3 exhibits a 2D sandwich-type structure. CP 4 can be described as a 4-connected 2D grid-like structure. CP 5 shows a 4-connected 3D cds framework with the topological symbol of {65·8}. CP 6 is a (4,4)-connected 3D framework with the {4·64·8}2{42·104} topology. The effects of functional groups and the number of the carboxyl groups of polycarboxylates on the structures of the title coordination polymers were discussed. The photocatalytic properties of CPs 1–6 were studied under UV irradiation, which have good photocatalytic degradation performance for anionic dye Congo red (CR). The possible photocatalytic mechanism was explored.

The application of NiCo-LDHs as electrode materials for supercapacitors has attracted widespread attention. However, pristine NiCo-LDHs always suffer from low conductivity and instability that limit their electrochemical performance in supercapacitors. Herein, we rationally engineered a novel KCu7S4@NiCo-LDH core–shell structure with good capacitive performance using a simple one-step solvothermal method and applied this structure as an electrode material for supercapacitors. KCu7S4 nanowires act as a dependable “skeleton” for supporting the NiCo-LDH nanosheets, thus preventing the aggregation of NiCo-LDHs and improving their conductivity. By controlling the reaction time and the ratio of Ni/Co in the precursor solution, according to the results of electrochemical testing, an optimal composite was obtained with Ni/Co = 2/1 and the reaction time of 8 h; the final KCu7S4@Ni2Co1-LDH composite possessed the high specific capacitance of 1104.5 F g−1 (122.7 mA h g−1) at 2 A g−1, good rate capability of 65.9% when the current density reached up to 10 A g−1, and a long-term stability (an 83.5% capacitance retention after 1000 cycles).

To research the effect of carboxylates on the assembly of Ni(II) coordination polymers, a naphthalene-amide ligand L (N,N′-bis(pyridin-3-ylmethyl)naphthalene-2,6-dicarboxamide) and five dicarboxylates [1,4-H2BDC = 1,4-benzenedicarboxylic acid, 1,4-H2PDC = 1,4-phenyldiacetic acid, 5-H2HIP = 5-hydroxyisophthalic acid, 3,4-H2TDC = 3,4-thiophenedicarboxylic acid, 2,5-H2TDC = 2,5-thiophenedicarboxylic acid] were selected to combine with Ni(II) under hydrothermal conditions. Five coordination polymers [Ni(L)(1,4-BDC)(H2O)2] (1), [Ni(L)(1,4-PDC)(H2O)2] (2), [Ni(L)(5-HIP)(H2O)2] (3), [Ni(L)(3,4-TDC)(H2O)2]·3H2O (4) and [Ni(L)(2,5-TDC)(H2O)]2·3H2O (5) were synthesized and structurally characterized by IR, PXRD and X-ray single-crystal diffraction. The title complexes show various structures: 2D 4-connected sql nets (1 and 2), a 3D cds framework of 3, 1D zigzag chain of 4 and 3D irl framework of 5. The electrochemical behaviors of 1–5 and the solid-state luminescence and fluorescence responses of 5 to Fe3+ and bovine serum albumin (BSA) were studied. Encouraged by functional thiophene components, 4 and 5 were used as catalyst precursors to synthesize carbon nanotubes (CNT-4 and CNT-5) by the chemical vapor deposition (CVD) method and characterized by XPS, SEM, TEM and Raman spectroscopy. The removals of contaminants (rhodamine B and Congo red) by 4 and 5 and their derivatives CNT-4 and CNT-5 in the aqueous phase were also comparatively investigated.

To investigate the effect of metal ions on the assembly of complexes derived from a semirigid tripodal carboxylic acid, 5-(4′-carboxylphenoxy) isophthalic acid (H3L), and two rigid chelating terminal N-donor ligands, dipyrazino[2,3-d:2′3′-f]quinoxaline (dpq) and dipyrido[3,2-a:2′,3′-c]phenazine (dppz), seven 0D → 3D complexes, [Cu(HL)(dpq)(H2O)2] (1), {[Co(HL)(dpq)(H2O)]·H2O}n (2), {[Ni3(L)2(dpq)3(H2O)4]·4H2O}n (3), {[Zn(HL)(dpq)(H2O)]·H2O}n (4), {[Cu2(L)(dppz)]·H2O}n (5), {[Co(HL)(dppz)]·H2O}n (6) and {[Ni3(L)2(dppz)3(H2O)3]}n (7), have been hydrothermally synthesized and structurally characterized by IR, TG and X-ray single-crystal diffraction analyses. Complex 1 is a 0D complex processing an unusual μ1-HL2− anion. Complex 2 features a 1D single chain based on Co(II) ions with a 6-coordinated mode. Complex 3 is the first (2,3,4)-connected 3D dpq-based framework derived from single/bimetallic mixed nodes with {83}2{84·122}{8} topology. Complex 4 is a 1D structure based on Zn(II) ions with a 5-coordinated mode. Complex 5 can be described as a 2D (6,3)-connected structure based on carboxyl-bridged Cu4 cores. Complex 6 is a 1D double chain derived from bimetallic nodes. Complex 7 exhibits a 2D double layer with (2,2,3,3,4)-connected nodes. The structural details of 1–7 were discussed. The solid-state luminescence properties of 1–7 and electrochemical properties of 1–3 have been investigated. The luminescence investigations show that 4 is an effective fluorescence probe for environmentally relevant Fe3+ ions. The electrochemical properties of a carbon paste electrode modified by the complexes 1–3 (1-CPE, 2-CPE and 3-CPE) were studied. 1-CPE has good electrocatalytic activity toward the reduction of nitrite, bromate and hydrogen peroxide in solution.

By introducing a quinoline–imidazole–monoamide ligand, N-(quinoline-5-yl)-1H-imidazole-4-carboxamide (L), into reaction systems containing a [Mo7O24]6− polyoxoanion and different metal ions, four octamolybdate-based complexes with the general formula of [M(HL)2(β-Mo8O26)] (M = Co (1), Ni (2), and Zn (3)) and [Cu2(HL)2(μ2-OH)2(β-Mo8O26)] (4) have been hydrothermally synthesized. All the complexes are 2D supramolecular structures with 1D chains based on the [β-Mo8O26]4− polyoxoanion. Complexes 1–3 are isostructural with the same architectural feature of a mononuclear [M(HL)2]4+ unit, but a binuclear [Cu2(HL)2(μ2-OH)2]4+ cation in complex 4, manifesting that the metal cation has a marked impact on the structures of 1–4. Meanwhile, the hydrogen bonding interaction between the protonated nitrogen atom of quinoline and the surface oxygen atom of the polyoxoanion demonstrates a crucial role in the formation of the supramolecular structure. All the complexes have better electrocatalytic activities, including not only the reduction properties of inorganic bromate, nitrite and hydrogen peroxide, but also the oxidation properties of ascorbic acid. In particular, 2-CPE can sense bromate and ascorbic acid with low detection limits of 1.67 and 6 μM. Both complexes 1 and 4 possess better photocatalytic properties for degrading organic dyes gentian purple and methylene blue, but only methylene blue for 3, accompanied by a weak antiferromagnetic behavior for complex 4.

To investigate the effects of metal ions and angles of the carboxyl groups of dicarboxylates on the structures of coordination polymers, four Zn(II)/Cd(II) coordination polymers [Zn(L)(1,4-BDC)]·H2O (1), [Zn(L)(1,3-BDC)]·H2O (2), [Zn(L)(1,2-BDC)] (3) and [Cd(L)0.5(1,2-BDC)(H2O)] (4) [L = N,N′-bis(pyridin-3-ylmethyl)-terephthalamide, 1,4-H2BDC = terephthalic acid, 1,3-H2BDC = isophthalic acid, 1,2-H2BDC = phthalate] were prepared under hydrothermal conditions. Polymers 1 and 2 are 2D structures with 63 and 44 topology. Polymer 3 shows a 4-connected 3D framework, and 4 features a 1D structure with single/double alternate linkers. The effects of the positions of carboxyl groups and the coordination characteristics of metal ions on the structures of the title coordination polymers were studied. The title coordination polymers show multi-functional fluorescence responses towards metal ions (Fe3+), anions (CrO42−, Cr2O72−) and pesticides (2,6-DC-4-NA) and good stability in a wide range of pH values. Taking 1 as an example, the mechanism was also explored by UV-visible absorption spectroscopy and the fluorescence lifetime experiment.

Here, we present that the shape and optical properties of CsPbBr3 nanocrystals (NCs) could be tuned by addition of various hydrohalic acids (HX, X = Cl, Br, I). The addition of hydrochloric acid (HCl) and hydrobromic acid (HBr) turns the nanocrystals from nanocubes (NCUs) to quantum dots (QDs). The optical properties are regulated by the composition and quantum confinement effect, while the hydrobromic acid (HBr) addition results in nanosheets (NSs), without a photoluminescence (PL) peak shift. Based on various characteristics, we speculate that the addition of HX leads to protonation of oleylamine from oleylamine into oleylammonium cations that compete with Cs+ during crystallization. The oleylammonium cations at the growing surface of NCs block further growth in the favored direction. Our study provides a facile strategy for tuning and manipulating the shape, size, and optical properties of all-inorganic CsPbX3 NCs and aids in the further exploration of the growth mechanism of perovskite NCs.

A Cd(II) metal–organic framework (MOF) [Cd3(L)(NTB)2(DMA)2]·2DMA (Cd-MOF, DMA = N,N-dimethylacetamide) was solvothermal prepared in the presence of N-donor ligand L (L = (E)-4,4′-(ethene-1,2-diyl)bis[(N-pyridin-3-yl)benzamide]) and O-donor ligand H3NTB (H3NTB = 4,4′,4′′-nitrilotribenzoic acid). The Cd-MOF is a 3D framework based on 2D [Cd3(NTB)2]n bilayers and semi-rigid bidentate L ligands, which exhibit a novel 2,3,6-connected network with {82·108·12·184}{8}6 topology. Moreover, the Cd-MOF represents the first metal–organic complex assembled by the H3NTB and bis(amide)-bis(pyridyl) co-ligands and displays remarkable fluorescence and stability as well as fluorescence quenching phenomenon towards Al3+, Cu2+, Cr3+, Fe3+ cations, Cr2O72− anion and nitrobenzene (NB). In particular, Cd-MOF can sensitively and selectively detect Fe3+, Cr2O72− and NB, and the limit of detection (LOD) values of Fe3+, Cr2O72− ions and NB are 5.1 × 10−5 M, 5.3 × 10−5 M and 4.2 × 10−5 M, respectively.

Two Zn2+-based luminescent metal–organic frameworks containing the same components, {[Zn(TIPA)pim0.5]2H2O·NO3}n (1) and {[Zn(TIPA)(pim)]3H2O}n (2) have been synthesized based on a π-electron rich semi-rigid triangular ligand TIPA (TIPA = tris(4-(1H-imidazol-1-yl)-phenyl)amine and H2pim = pimelic acid). 1 is a two-fold interpenetrating 3D framework containing four chiral (10,3)-a subnets, and 2 is merely a 2D + 2D → 2D entangled network, although they were synthesized from the same starting materials. A photoluminescence investigation revealed that the emissions of 1 and 2 entirely originate from the intraligands charge transfer transitions (π → π*). Metal–organic framework 1 can be applied as a dual functional chemical sensor for nitroaromatic (NAC) compounds and antibiotics detection with a high sensitivity and quick response. In addition, the effective detection of nitroaromatic compounds and antibiotics was rationalized by the density functional theory (DFT) calculation of the energy bands of the NAC compounds and antibiotics, which revealed that a photoinduced electron transfer mechanism is largely responsible for the sensing of nitroaromatic compounds, and the resonance energy transfer is largely responsible for the exclusive sensing of ofloxacin (OFX).

Under the regulation of different metal ions and organic ligands, five isopolymolybdate-based complexes, namely, [CoL10.5(Mo3O10)(H2O)2]·2H2O (1), [NiL10.5(Mo3O10)(H2O)2]·2H2O (2), [ZnL1(H2O)3][γ-Mo8O26]0.5 (3), [CdL11.5(θ-Mo8O26)0.5]·2H2O (4), and [ZnL2(Mo3O10)]·H2O (5) (L1 = 1,4-bis(1H-pyrazole-4-carboxamide)p-phenylene, L2 = 1,2-bis(1H-imidazole-4-carboxamido)ethyl) were prepared under hydrothermal/solvothermal conditions. Complexes 1, 2, and 4 were obtained under solvothermal conditions. 1 and 2 were isostructural, composed of [M2L1(H2O)4]4+ (M = CoII/NiII) cationic units and [Mo3O10]n2n− polymolybdate chains. In the presence of Cd ions, the 2D network structure of 4 was constructed from the [θ-Mo8O26]4− anions bridged by metal–organic belts. Both 3 and 5 were isopolymolybdate-based ZnII-complexes synthesized under hydrothermal conditions except for the difference of organic ligands and pH, namely, L1 acted as the ligand and the pH was 3.5 for 3, but they were L2 and 3.4 for 5, respectively. Complex 3 had a 2D supramolecular structure containing cationic units ZnL1(H2O)32+ and 1D infinite inorganic chains [γ-Mo8O28]n. In 5, the 1D convergent chains [Mo3O10]n were connected by binuclear metal–organic cationic rings [Zn2L22]4+ to form a 2D structure. The solvent ratio and reaction pH had a great influence on the synthesis of the title complexes, and metal ions and ligands played important roles in regulating the diversity of the polymolybdates and the structures of the complexes. The electrochemical, luminescence, and photocatalytic degradation properties for MB of the title complexes were investigated.

To study the effects of carboxylates on the assembly and structures of Ni(II) coordination polymers (CPs) based on a phenyl/methylene-mixed-bridged bis-pyridyl-bis-amide [N,N′-bis(4-methylenepyridin-4-yl)-1,4-benzenedicarboxamide] (L) ligand, ten 1D → 3D Ni(II) CPs, namely [Ni(L)(2-NB)2(H2O)2] (1), [Ni(L)(4-NB)2(H2O)2] (2), [Ni(L)2(2-MOB)2] (3), [Ni(L)2(3-CB)2] (4), [Ni(L)(2-CP)(H2O)] (5), [Ni(L)(5-NIP)(H2O)2]·2H2O (6), [Ni(L)(3-NP)(H2O)2] (7), [Ni(L)(4,4′-OBA)]·H2O (8), [Ni(L)(1,4-BDC)(H2O)2]·2H2O (9) and [Ni(L)(1,4-CHDA)(H2O)2]·4H2O (10) [2-nitrobenzoic acid (2-HNB), 4-nitrobenzoic acid (4-HNB), 2-methoxybenzoic acid (2-HMOB), 3-chlorobenzoic acid (3-HCB), 2-carboxyphenylacetic acid (2-H2CP), 5-nitroisophthalic acid (5-H2NIP), 3-nitrophthalic acid (3-H2NP), 4,4′-oxybis(benzoic acid) (4,4′-H2OBA), 1,4-benzenedicarboxylic acid (1,4-H2BDC) and trans-1,4-cyclohexanedicarboxylic acid (1,4-H2CHDA)], have been hydrothermally synthesized with various carboxylates and structurally characterized by IR, PXRD and X-ray single-crystal diffraction. 1 and 2 are similar 1D coordination polymers. 3 and 4 feature similar 2D coplanar 4,4-connected networks extended by single L linkers. 5 displays a 2D wave-like 4,4-connected network based on L and 2-CP mixed linkers. 6 shows a 2D 4,4-connected structure derived from L and 5-NIP mixed spacers. 7 is a CdSO4 type 4-connected 3D framework. 8 displays a 2D → 3D parallel polycatenation array based on 2D (4,4)-connected wave-like coordinated layers. 9 and 10 feature similar 2D → 3D inclined polycatenation arrays based on 2D (4,4)-connected coplanar networks. The effects of the carboxylates on the structures of the title complexes are discussed in detail. The solid-state luminescent and fluorescent sensing properties of 1–10 for Fe3+ ions were investigated. Moreover, the effects of 1, 5 and 7 on the fluorescence properties of bovine serum albumin (BSA) and the electrocatalytic activities of carbon paste electrodes (CPEs) bulk-modified with 1, 3, 5, 7 and 9 for the reduction of hydrogen peroxide, bromate and nitrite were studied.

By changing solvent systems, five new Anderson-type polyoxometalates (POMs)-based metal–organic complexes, namely, {(H2PCAP′)2[CrMo6(OH)5O19]}·H2O (1), {Cu3(PCAP)2[CrMo6(OH)5O19](H2O)3(DMF)2}·4H2O·2HCHO (2), {Cu3(PCAP)2[CrMo6(OH)6O18]Cl(H2O)5}·10H2O (3), {Co3(PCAP)2[CrMo6(OH)5O19](H2O)6}·9H2O·HCHO (4) and {Co3(HPCAP)2[CrMo6(OH)6O18]2(H2O)10}·7H2O·2CH3CH2OH (5) (HPCAP = 3-(2-pyridinecarboxylic acid amido)pyridine, PCAP′ = 3-(pyridinecarboxylic acid)amido pyridine), were successfully synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Complex 1 was obtained with H2O as the solvent and exhibited a 3D supramolecular network based on CrMo6 anions and protonated H2PCAP′ molecules via hydrogen bonds. It should be noted that the PCAP′ was in situ transformed from HPCAP. Complexes 2–5 were synthesized with different mixed solvents. In complex 2, the CrMo6 anions acted as an inorganic bridging ligand to link the 1D [Cu3(PCAP)2]n4n+ chains to construct a 2D layer. Complexes 3 and 4 showed similar 3D frameworks. Two orientations of metal–organic loops [M2(PCAP)2] (M = Cu for 3, Co for 4) could be observed, which directly extended the 1D M–CrMo6 chains into 3D networks with a 3,3,4,4-connected {42·123·14}{42·6}2 topology. In 5, the 1D Co–CrMo6 inorganic chain, [Co2(PCAP)2] binuclear loop unit and discrete CrMo6 polyanion were connected with each other by hydrogen-bonding interactions to form a 1D ladder-like supramolecular dual chain. The structural diversities showed that the solvents play key roles in the construction of various architectures and in the in situ transformation of HPCAP. The adsorption behaviours of the title complexes for organic dyes were investigated in detail. All of the title complexes showed an efficient adsorption capacity for the cationic dyes gentian violet (GV) and methylene blue (MB). In particular, complex 4 could selectively separate GV from the mixture of GV&RhB and GV&MO within 5–10 min, which can be used as a chromatography column for dye removal. In addition, the electrochemical properties of the title complexes were also studied.

Three novel polyoxometalate (POM)-based metal–organic complexes (MOCs) constructed from rigid pyridyl-triazole-tetrazole and pyridyl-bis(triazole) ligands have been hydrothermally synthesized and structurally characterized: [Co3(Htyptz)2(γ-Mo8O26)(H2O)6]·4H2O (1), H2[Co3(Htyptz)2(TeMo6O24)(H2O)8]·6H2O (2), [Co3(Hpyttz)2(γ-Mo8O26)(H2O)8]·2H2O (3) (H2typtz = 3-(tetrazol-5-yl)-5-(pyrid-3-yl)-1,2,4-triazolyl, H2pyttz = 3-(pyrid-4-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl). Single-crystal X-ray diffraction analyses reveal that complex 1 is a 3D metal–organic framework. Both 2 and 3 are 2D metal–organic architectures. In complex 1, the adjacent [γ-Mo8O26]4− anions are linked by the CoII ions to form a 1D Co-γ-Mo8O26 inorganic chain. Then the 1D Co-γ-Mo8O26 inorganic chains are linked together by the 1D metal–organic Co-Htyptz chains to form a 3D framework. In complex 2, the adjacent Co-Htyptz metal–organic chains are connected by TeMo6 polyoxoanions to form a 2D architecture. In complex 3, [γ-Mo8O26]4− anions are bridged by the CoII ions to give similar 1D Co-γ-Mo8O26 inorganic chains to those in 1, which are connected through [Co(Hpyttz)2] units to form a 2D network. 1 and 2 represent the first examples of POM-based MOCs derived from H2typtz. The effects of the POM type and different ligands on the structures of the title complexes were discussed. The adsorption activities for organic dyes methylene blue (MB), gentian violet (GV), methyl orange (MO), rhodamine B (RhB), neutral red (NR) and safranin T (ST) have been investigated in detail. Furthermore, the electrochemical properties of 1 and 2 have been studied, which display electrocatalytic activities toward the reduction of nitrite and bromate. 1-CPE shows pH-dependent electrochemical behaviors and may be used as a potential sensor.

Three novel Anderson-type polyoxometalates (POMs)-based metal–organic complexes (MOCs), namely, [Mn2(4-pdtz)2[CrMo6(OH)5O19](H2O)4] (1), {Mn(3-dpye)0.5[CrMo6(OH)6O18](H2O)}·(3-H2dpye)0.5 (2), [Mn2(3-H2dpye)(TeMo6O24)(H2O)6]·4H2O (3) (4-pdtz = 4-pyridino-bistriazol, 3-dpye = N,N′-bis(3-pyridinecarboxamide)-1,2-ethane), were hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). In complex 1, the [CrMo6(OH)5O19]4− (CrMo6) polyoxoanions bridge the MnII ions to generate a 1D Mn–CrMo6 inorganic chain, on which the 4-pdtz ligands hang. In 2, the adjacent CrMo6 polyoxoanions are linked by MnII ions to form a 2D inorganic layer, which is further linked by 3-dpye forming a 3D metal–organic framework (POMOF). Interestingly, the large voids of the 3D POMOF accommodate free protonated 3-H2dpye molecules. In complex 3, the adjacent TeMo6O246− (TeMo6) polyoxoanions are linked by MnII ions to form a 1D inorganic chain, the protonated 3-H2dpye act as bidentate ligands connecting two MnII centers with the oxygen atoms from amide groups, forming a steady 2D metal organic layer. The effects of various coordination behaviors of the pyridyl-based ligands and central metal ions on the structures of the title complexes have been discussed. The title complexes exhibit excellent electrocatalytic activity towards the reduction of bromate and hydrogen peroxide. In addition, the redox potentials of complex 3 is highly sensitive to pH and may be used as a kind of potential pH sensor. The photocatalytic properties of the title complexes under UV and visible irradiation have been investigated in detail.

Six new CoII coordination polymers (CPs) based on a bi-methylene-bridged semi-rigid bis-pyridyl-bis-amide ligand and various polycarboxylates, namely, [Co(4-bmbpd)(1,4-BDC)(H2O)2]·2H2O (1), [Co(4-bmbpd)(OBA)]·H2O (2), [Co(4-bmbpd)(2,2′-BDC)]·H2O (3), [Co(4-bmbpd)(5-NIP)]·2H2O (4), [Co(4-bmbpd)0.5(5-AIP)]·H2O (5), and [Co3(4-bmbpd)3(1,3,5-BTC)2(H2O)4]·4H2O (6) [4-bmbpd = N,N′-bis(4-methylenepyridin-4-yl)-1,4-benzenedicarboxamide, 1,4-H2BDC = 1,4-benzenedicarboxylic acid, H2OBA = 4,4′-oxybisbenzoic acid, 2,2′-H2BDC = 2,2′-biphenyldicarboxylic acid, H2NIP = 5-nitroisophthalic acid, 5-H2AIP = 5-aminoisophthalic acid, and 1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid] have been synthesized and structurally characterized by single-crystal X-ray diffraction analyses, IR spectroscopy, thermal gravimetric analyses (TG) and powder X-ray diffraction (PXRD). Complex 1 is a 2D 4-connected layer structure consisting of 1D [Co-(4-bmbpd)]n wave-like chains and [Co-(1,4-BDC)]n linear chains. 2 is also a 2D 4-connected network composed of 1D [Co-OBA]n linear chains and [Co-(4-bmbpd)]n wave chains. Complex 3 shows a (3,5)-connected 2D architecture based on 1D [Co-BDC]n double linear chains and 1D [Co-(4-bmbpd)]n zigzag chains with a {42·67·8}{42·6} topology. In 4, two 4-bmbpd ligands coordinate with two CoII ions in an anti-configuration to form a 38-membered [Co2(4-bmbpd2)] loop, which is further extended into a 1D tubular structure by pairs of 5-NIP anions. Coordination polymer 5 is a 3D (4,5)-connected architecture with a {44·62}{44·66} topology. 6 shows a 3D (2,3,4,4)-connected framework, which contains 1D [Co-1,3,5-BTC]n double chains. The CoII ion and 4-bmbpd ligand in the title coordination polymers show different coordination characters and conformations. The effect of organic polycarboxylates with different rigidities/lengths/substituents on the structures of CoII coordination polymers was investigated. The electrochemical behaviors of 1–3, 5 and 6, the fluorescent behaviors of 5 and 6, and the photocatalytic activities of 5, 6, and Fe3+-functionalized Fe3+@5 and Fe3+@6 composites were investigated.

Three octamolybdate-based metal–organic complexes constructed from a pyridyl-carboxylate ligand containing an amide group, 3-(2-pyridinecarboxylic acid)amido pyridine (HPCAP), namely, H2{[Cu3(PCAP)4(H2O)2](β-Mo8O26)}·10H2O (1), H{[Cu(PCAP)(H2O)](β-Mo8O26)0.5} (2) and H2[Co(H2O)6][Co2(PCAP)4(γ-Mo8O26)(H2O)2]·10H2O (3), have been successfully synthesized under hydrothermal or solvothermal (methanol–water mixed solvent) conditions. Single-crystal X-ray analyses reveal that compound 1 is a 2D layer based on infinite 1D [Cu3(PCAP)4]n2n+ chains and bidentate β-Mo8O264− anions. In compound 2, 1D “thin centipede” [Cu2(PCAP)2]n2n+ chains were connected by tetradentate β-Mo8O264− anions through the Cu–O bond to form a 2D network. In compound 3, γ-Mo8O264− anions were connected by adjacent [Co2(PCAP)4(H2O)2] moieties through Co–O and Mo–N bonds forming an uncommon 1D “fat centipede” chain. The adjacent chains were further extended to a 2D supramolecular network through hydrogen bonding interactions. The title compounds represent the first examples of introducing a pyridyl-carboxylate ligand containing an amide group into the POM system. The pH value, solvent and metal ions play key roles in the construction of the final architectures and show a great influence on the structural diversities of the title compounds. The electrochemical properties of compound 1 and the photocatalysis properties of the title compounds have been reported.

By introducing a tetrazole- and pyridyl-containing asymmetric amide ligand into polyoxometalate (POM) systems, four POM-based complexes, namely, H4[Cu2(TAAP)4(H2O)](Mo8O26)2·20H2O (1), H2[Co(TAAP)2(H2O)2](Mo8O26)·11H2O (2), H2[Ag4(TAAP)4(H2O)2(PMo12O40)2]·4H2O (3), and H4[Ag2(AAP)4(PW12O40)2]·2AAP·12H2O (4) (TAAP = 3-(1H-tetrazole-1-acetic acid amido) pyridine; AAP = 3-(acetic acid amido) pyridine), have been prepared under solvothermal (methanol–water mixed solvent) or hydrothermal conditions and structurally characterized. Compounds 1 and 2 are isostructural 3D structures, which are based on 3D [M(TAAP)2]n2n+ metal–organic frameworks and noncoordinated [Mo8O26]4− polyanion templates. Compound 3 exhibits a dimeric structure constructed from two Keggin [PMo12O40]3− anions and a tetranuclear [Ag4(TAAP)4(H2O)2]4+ subunit. Compound 4 exhibits a 2D supramolecular network based on 1D infinite chains, which are constructed by [PW12O40]3− and Ag-AAP subunits. In compound 4, the AAP ligand was in situ transformed from TAAP. The structural diversities show that POMs play key roles in the construction of final architectures and the in situ transformation of TAAP. The title compounds represent the first examples of introducing tetrazole- and pyridyl-containing asymmetric amide ligand into the POM system. The electrochemistry, photocatalysis and photoluminescence properties of the title compounds have been reported.

Five new coordination polymers (CPs), namely, [Cu(3-bpcb)(1,2-pda)]·2H2O (1), [Cu(4-bpah)(1,2-pda)(H2O)]·H2O (2), [Ni2(4-bpah)2(1,2-pda)2(μ2-H2O)] (3), [Cu3(4-bpfp)(1,2-pda)2(μ3-OH)2] (4), [Co(4-bpfp)0.5(1,2-pda)(H2O)] (5), were prepared by hydrothermal reactions of metal(II) chloride with 1,2-H2pda (H2pda = 1,2-phenylenediacetic acid) in the presence of different bis(pyridyl)-bis(amide) ligands (3-bpcb = N,N′-bis(3-pyridinecarboxamide)-1,4-benzene; 4-bpah = N,N′-bis(4-pyridinecarboxamide)-1,2-cyclohexane; and 4-bpfp = N,N′-bis(4-pyridylformyl)piperazine) and structurally characterized by single crystal X-ray diffraction, infrared spectroscopy (IR), elemental analysis, powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA). Complexes 1–3 show three different 2D layers with diverse (42·67·8)(42·6), (44·62) and (42·6)(42·67·8) topological structures, respectively. Complex 4 exhibits a 3D polymeric framework, which presents a novel (3,4,8)-connected topology with the Schlafli symbol (3·4·5)2(32·42·52·614·74·83·9)(32·63·7). Complex 5 displays a 3D network with 3,4-connected (42·63·8)(42·6) topology. The diverse arrangements of these complexes show the remarkable sensitivity of the metal(II)–H2pda system to the different bis(pyridyl)-bis(amide) ligands. In addition, the electrochemical properties of complexes 3–5 and the dye adsorption properties of the title complexes are also discussed.

A series of new Co(II) complexes based on a new semi-rigid “V”-like bis-pyridyl-bis-amide derivative, namely, [Co(3-bpha)2(2,3-HPDC)2] (1), [Co(3-bpha)(3-NPH)(H2O)2]·2H2O (2), [Co(3-bpha)(1,3-BDC)]·4H2O (3), [Co(3-bpha)(HIP)]·3H2O (4), [Co(3-bpha)(MIP)(H2O)]·H2O (5), and [Co3(3-bpha)2(1,3,5-BTC)2(H2O)4]·2H2O (6) (3-bpha = N,N′-bis(pyridin-3-yl)-5-hydroxybenzene-1,3-dicarboxamide, 2,3-H2PDC = 2,3-pyridinedicarboxylic acid, 3-H2NPH = 3-nitrophthalic acid, 1,3-H2BDC = 1,3-benzenedicarboxylic acid, H2HIP = 5-hydroxyisophthalic acid, H2MIP = 5-methylisophthalic acid, 1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid), have been hydrothermally synthesized by tuning aromatic polycarboxylate co-ligands and characterized by single-crystal X-ray diffraction, IR spectra, powder XRD and TG analysis. Complex 1 is a discrete zero-dimensional (0D) structure in which the 3-bpha ligands and the 2,3-HPDC anions act as the terminal groups simultaneously to coordinate with the CoII ions. Complex 2 is a 1D meso-helical chain in which the 3-bpha ligands show a μ2-bridging mode and the 3-NPH anions act as the terminal groups. In complexes 3 and 4, pairs of 3-bpha ligands integrate with two CoII ions to generate 28-membered Co2(3-bpha)2 rings, which connect with the 1D [Co-1,3-BDC]n or [Co-HIP]n chains to create the 2D networks. In complex 5, the CoII ions are linked to 3-bpha ligands, resulting in a single-strand [Co-3-bpha]n helix chain, which is further connected to the MIP anions to form a 2D network. Complex 6 shows a 3D framework with (3,3,4)-connected (83)4(84·102) topology, which contains [Co-(1,3,5-BTC)]n 2D grid-like sheets and 1D [Co-3-bpha]n helical chains. Finally, the 0D discrete architecture in 1, 1D chain in 2, and 2D networks in 4 and 5 are extended to 3D supramolecular frameworks through hydrogen-bonding interactions. The effect of polycarboxylate auxiliary ligands with different substitute groups and different carboxyl positions and number on the assembly and structures of the target complexes were discussed. Moreover, the thermal stabilities, electrochemical properties and photocatalytic activities of complexes 1–6 were investigated.

A series of polyoxometalate (POM)-based metal–organic complexes constructed from a semi-rigid bis-pyridyl-bis-amide ligand have been hydrothermally synthesized and structurally characterized: [Cu2L2(PMoVI11MoVO40)(H2O)2]·2H2O (1), [Cu2L2(PWVI11WVO40)(H2O)6]·H2O (2), [Cu2L2(SiW12O40)(H2O)6]·H2O (3) and [Cu2L2(H2K2Mo8O28)(H2O)2] (4) (L = N,N′-bis(3-pyridinecarboxamide)-piperazine). Single-crystal X-ray analyses reveal that complex 1 is a 2D metal–organic architecture based on the Keggin-type [PMoVI11MoVO40]4− anions and quadrate Cu2L2 loops. Isostructural complexes 2 and 3 display 2D supramolecular networks based on 1D infinite chains, which are constructed from quadrate Cu2L2 loops and Keggin polyoxoanions. Complex 4 exhibits a 3D metal–organic framework derived from the newly-reported [K2Mo8O28]6− polyoxoanions and quadrate Cu2L2 loops. The L ligands show a μ3-bridging coordination mode (via ligation of two pyridyl nitrogen atoms and one carbonyl oxygen atom) in 1 and 4, and a μ2-bridging coordination mode (via ligation of two pyridyl nitrogen atoms) in 2 and 3, forming Cu2L2 loops in 1–4. The influence of amide group coordination modes and structural features of POMs on the structures of the title complexes has been discussed. The electrochemical properties and selective photocatalytic properties of the title complexes have been reported in this article.

A series of polyoxometalate (POM)-based metal–organic complexes containing multinuclear Cu(II) clusters with a 4-amino-1,2,4-triazole (4-atrz) ligand, namely, [Cu3(4-atrz)8(PMo12O40)2(H2O)2]·2H2O (1), [Cu2(4-atrz)6(SiW12O40)(H2O)]·6H2O (2), [Cu2(4-atrz)4(μ2-OH)(CrMo6(OH)6O18)]·3H2O (3), [Cu3(4-atrz)3(Mo8O27)(H2O)4]·6H2O (4) and [Cu3(4-atrz)3(V10O30)0.5(μ3-OH)(H2O)]·H2O (5) have been synthesized by selectively adding additional citric acid or boric acid under hydrothermal conditions and have been structurally characterized by single-crystal X-ray diffraction and powder X-ray diffraction. Compound 1 has a zero-dimensional (0D) architecture, which is constructed from a linear trinuclear cluster [Cu3(4-atrz)8(H2O)2]6+ and two Keggin PMo12O403− anions. Compound 2 shows a 1D zigzag chain, in which the binuclear [Cu2(4-atrz)6(H2O)]4+ clusters and Keggin SiW12O404− anions connect to each other. Compound 3 is a 1D linear chain based on linear [Cu3(4-atrz)6]6+ clusters; the [CrMo6(OH)6O18]3− anions hang on two sides of the 1D chain. Compound 4 has a 2D layer constructed from trigonal [Cu3(4-atrz)3(H2O)4]6+ clusters and rare infinite [Mo8O27]n6n− chains. The [Mo8O27]6− anion is transformed from the Anderson-type [CoMo6(OH)6O18]3− anion, which is also rare in the POM-based reaction system. Compound 5 has a 3D framework constructed from trigonal trinuclear [Cu3(4-atrz)3(OH)]5+ clusters and rare [V10O30]10− polyanions, which represents the first example of a V10O30-based 3D metal–organic complex. Structural analyses indicate that different POMs show great effect on the various structures of 1–5 and the additional acids play an important role in the formation of 1–5. Photocatalytic experiments of 1–5 on degradation of three organic dyes (methylene blue, Rhodamine B and methyl orange) manifest that compounds 1–3 are good candidates for the photocatalytic degradation of methylene blue, and compound 1 is a good photocatalyst for the degradation of Rhodamine B.

Three lead metal–organic complexes, namely, [Pb(tpphz)(L1)(H2O)]·3H2O (1), [Pb(tpphz)1.5(L2)0.5(NO3)]·H2O (2) and [Pb3(tpphz)2(L3)3]·2H2O (3) {H2L1 = biphenylethene-4,4′-dicarboxylic acid, H2L2 = decanedioic acid, H2L3 = octanedioic acid, tpphz = tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j]phenazine} have been synthesized by employing a double phenanthroline derivative tpphz as the main ligand in the presence of different organic dicarboxylates under hydrothermal conditions. Single crystal X-ray diffraction analyses reveal that a bimetallic nano-ring complex (1) was obtained by using a long and rigid aromatic dicarboxylate (L1), and a 1D zigzag coordination polymer (2) was synthesized in the presence of a flexible fatty dicarboxylate (L2). When a shorter flexible fatty dicarboxylate (L3) was used then an unprecedented 0D + 3D cocrystal (3) was prepared. The tpphz ligands exhibited versatile coordination modes. The organic dicarboxylates with different flexibility and spacer length play an important role in adjusting the dimensions of the title lead complexes. Moreover, the thermal stability and fluorescent properties of complex 3 were also investigated.

Using the mixed ligands bis(3-pyridylformyl)piperazine (3-bpfp) and 5-nitroisophthalic acid (H2NIPH) or 3-nitrophthalic acid (H2NPH), four two dimensional (2D) copper or cadmium coordination polymers with different structural features formulated as [Cu(3-bpfp)(NIPH)(H2O)] (1), [Cu(3-bpfp)0.5(NPH)(H2O)2] (2), [Cd(3-bpfp)0.5(NIPH)] (3), and [Cd(3-bpfp)(NPH)(H2O)]·H2O (4) have been hydrothermally synthesized and structurally characterized. Single-crystal X-ray diffraction analyses indicate that complex 1 displays a new contorted 2D layer consisting of two kinds of tetranuclear cycles with different dimensions: A-cycle of 20.53 × 9.57 A and B-cycle of 19.17 × 12.07 A, in which CuII ions are knitted by the 3-bpfp ligands with μ2-bridging coordination mode (via ligation of nitrogen atoms in pyridyl rings) and NIPH. In complex 2, CuII centers are connected by the ligands NPH to form one dimensional (1D) CuII-NPH left- and right-handed helical chains, and these chains are extended into 2D layer network by the 3-bpfp ligands with μ2-bridging coordination mode. Only one hexanuclear cycle with dimension of 16.86 × 11.10 A was included in the 2D structure of 2. Complex 3 contains two types of 1D ladder-like chains composed of CdII ion, the 3-bpfp ligand with μ4-bridging coordination mode (via ligation of nitrogen atoms in pyridyl rings and oxygen atoms in carbonyl groups) and bridging NIPH ligand with two coordination modes (chelate-monodentate mode and chelate mode), forming a double layer 2D network with the (42·6)(42·84)(47·63) topology. Complex 4 possesses 2D sheet based on the 1D right-handed helical chains constructed from the CdII ions and the NPH ligands with bis-chelating coordination mode, and the 3-bpfp ligands with μ2-bridging coordination mode. Moreover, the 2D structures of complexes 1–4 are ultimately packed into three dimensional (3D) supramolecular frameworks through the hydrogen bonding or the π–π stacking interactions. In addition, the fluorescent properties of the title complexes and the electrochemical behaviors of 1–2 at room temperature have been investigated.

Five new compounds of sulfonylcalix[4]arenetetrasulfonate (SC4AS), [H7Na(H2O)3(SC4AS)(phen)5](H2O)11.9 (1), [H6Mn(H2O)4(SC4AS)(phen)5] (H2O)12.7 (2), [Cu4 (SC4AS) (phen)6] (H2O)4.5 (3), {[Cu2(SC4AS) (bpy)2][Cu(bpy)2(H2O)]2} (H2O)6.6 (4), and {[Zn2(SC4AS) (phen)2][Zn(phen)2(H2O)2]2} (H2O)7 (5) (where phen = 1,10-phenanthroline and bpy = 2,2′-bipyridine), were synthesized by a hydrothermal method and structurally determined by single crystal X-ray diffraction. The SC4AS ligand adopts partial cone conformation in compounds 1 and 2 and 1,2-alternate form in compounds 3–5. According to the structural analysis and density functional theory (DFT) calculations, we suggest that the metal can affect the conformation of SC4AS. In addition, the introduction of other ligands such as phen also affects the conformation of SC4AS.

Five new Zn(II) metal–organic coordination polymers, [Zn2(L1)2(Dpq)2]·H2O (1), [Zn(L2)(Dpq)(H2O)] (2), [Zn(L3)(Dpq)(H2O)]2 (3), [Zn(Dpdq)(L3)] (4) and [Zn(Dpdq)(L4)]·H2O (5) (Dpq = dipyrido[3,2-d∶2′,3′-f]quinoxaline, Dpdq = 2,3-di-2-pyridylquinoxaline, H2L1 = benzene-1,2-dicarboxylic acid, H2L2 = benzene-1,3-dicarboxylic acid, H2L3 = benzene-1,4-dicarboxylic acid, H2L4 = biphenyl-4,4′-dicarboxylic acid), have been hydrothermally synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that complexes 1–4 possess chain structures which are further assembled to form four three-dimensional (3-D) frameworks by π–π stacking and/or hydrogen-bonding interactions, while a similar chain of 5 has a two-dimensional (2-D) network packed by π–π stacking and hydrogen-bonding interactions. In 1–3, the Dpq ligand takes a chelating coordination mode while the other two nitrogen atoms did not coordinate to the Zn(II) ions. In 4 and 5, the Dpdq ligands have two coordination modes. The structural differences of the benzenedicarboxylate ligands and N-containing rigid/flexible chelating ligands have a great influence on the geometries of the corresponding complexes. This result also shows that intramolecular/intermolecular weak interactions play an important role in the formation of supramolecular networks, especially in linking low-dimensional entities into high-dimensional supramolecular frameworks. In addition, complexes 1 and 3–5 exhibit blue emission in the solid state at room temperature.

Four new hexavanadate cluster-based hybrid materials [Ni(3-atrz)2V2O6]·2H2O (1) and [M3(4-atrz)6V6O18]·4H2O [atrz = amino-1,2,4-triazole; M = Ni (2), Co (3) and Zn (4)] have been synthesized under hydrothermal conditions by the reaction of transition metal salts, amino-triazole ligands and sodium metavanadate. Single crystal X-ray diffraction analyses reveal that compound 1 shows a one-dimensional (1D) chain formed by the alternative arrangement of linear trinuclear complexes [Ni3(3-atrz)6]6+ and hexanuclear [V6O18]6− clusters. Compounds 2–4 are isostructural three-dimensional (3D) frameworks, which are constructed from the linear trinuclear transition metal complexes and 2D inorganic layers derived from transition metal ions and hexanuclear [V6O18]6− clusters. The distinct amino positions in the two types of triazole ligands play the key role in determining the final dimensionality and structures of the title compounds. The thermal stability, photocatalytic activity and magnetic properties of 1–4 have been investigated.

By using an uncommon bi(triazole) ligand and tuning the substituent group on the ligand in the Ag–polyoxometalate (POM) reaction system, three new three-dimensional (3D) Keggin-based metal–organic complexes (MOCs), [Ag4(L1)2(PWVI11VVO40)]·∼14H2O (1), Ag4(L1)2(HSiWVI11VVO40)]·∼25H2O (2) and [Ag4(L2)2(H2O)2(PWVI11VVO40)]·2H2O (3) (L1 = 4-(1H-1,2,4-triazol-3-yl)-2H-1,2,4-triazolyl and L2 = 3-(pyrid-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), have been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction, IR spectra and elemental analyses. In compounds 1–3, the Keggin-type POMs act as highly connected inorganic ligands and are modified by the Ag–triazole polymeric motifs. Compounds 1 and 2 exhibit similar (4,4,4,5,10)-connected 3D frameworks with {414·616·815}{44·62}3{46}{49·6}2 topologies, which are constructed from infinite one-dimensional (1D) [Ag4(L1)2]n chains and 10-connected polyoxoanions. Compounds 1 and 2 represent the first examples of coordination complexes using bi(triazole) as a ligand. In compound 3, there is a twisted 1D chain consisting of [Ag4(L2)2]4+ subunits, which are linked by 6-connected Keggin anions to generate a complicated 3D framework with a {4·6·8}{42·62·82}{42·6}{43·62·8}{43·63}{43·64·85·103}{44·62} topology. The substituent group on the bi(triazole) plays a key role in the assembly and structures of the title compounds. The photocatalytic activities and selectivities, and the electrochemical properties of compounds 2 and 3 have been investigated.

Six new transition metal coordination polymers, namely, [Co(1,2-BDC)(L)1.5(H2O)] (1), [Co(1,3-BDC)(L)(H2O)2]·H2O (2) [Co(5-AIP)(L)0.5(H2O)]·2H2O (3), [Cu(1,2-BDC)(L)] (4), [Cu(1,3-BDC)(L)(H2O)]·3H2O (5), and [Cu2(5-AIP)2(L)2(H2O)]·6H2O (6) (L = N,N′-di(3-pyridyl)octanediamide, 1,2-H2BDC = 1,2-benzenedicarboxylic acid, 1,3-H2BDC = 1,3-benzenedicarboxylic acid, 5-H2AIP = 5-aminoisophthalic acid), have been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. In compound 1, the adjacent CoII ions are connected by L ligands to form a 1D chain with an alternating arrangement of L ligands and Co2L2 dinuclear loops. The 1,2-BDC anions coordinate with one CoII ion in a bis(monodentate) chelate mode. Complex 2 shows a 2D (44) grid network with the sql topology, which consists of the 1D zigzag [Co–L]n chain and 1D linear [Co-1,3-BDC]n chain. When 5-H2AIP is used in compound 3, an interesting 2D terraced-type layer based on 1D [Co-5-AIP]2n ladder-like chains and μ2-bridging L ligands with 3,4-connected {62.10}{6} topology is formed. Under the similar conditions to compound 1, except that the cobalt(II) salt is replaced by a copper(II) salt, a 2D wave-like network 4 with 2,4-connected {64.8.10}{6} topology is obtained. Compound 5 displays a 3D coordination polymeric architecture based on 1D [Cu-1,3-BDC]n chains and [Cu–L]n chains, which represents an intriguing 3-fold interpenetrating framework with CdSO4-type topology. When 1,3-BDC is replaced by 5-AIP, another 3-fold interpenetrating 3D CdSO4-type coordination framework for compound 6 is obtained, which is constructed from three types of 1D chains: [La–Cu–Lc]n chain, [Lb–Cu–Lb]n chain and [Cu-5-AIP]n chain. The adjacent 1D chains for 1 and 2D layers for compounds 2, 3 and 4 are further extended by hydrogen bonding interactions to 3D supramolecular frameworks. The effect of dicarboxylates and central metals on the structures of the title complexes has been discussed. Furthermore, the electrochemical behaviors and solid state fluorescent properties for compounds 1–6 are investigated.

Four new d10 metal–organic coordination polymers tuned by the “V”-shaped tri-pyridyl–bis-amide ligands with different spacers, namely, [Zn(L1)(BDC)]·H2O (1), [Cd(L1)(BDC)]·H2O (2), [Zn(L2)(BDC)] (3) and [Cd(L2)(BDC)] (4) (L1 = N,N′-bis(pyridine-3-yl)pyridine-2,6-dicarboxamide, L2 = N,N′-bis(pyridine-3-yl)pyridine-3,5-dicarboxamide, H2BDC = 1,4-benzenedicarboxylic acid) have been synthesized under hydrothermal conditions. In complexes 1 and 2, the metal ions are linked by L1 to form left- and right-helical Zn/Cd–L1 chains, which are further extended into two-dimensional (2D) wave-like layers by BDC anions. In 3, two L2 ligands link two ZnII ions forming the Zn2(L2)2 loops, which are connected by BDC anions to form a (2·65) topological 2D network. In addition, the large Zn2(L2)2 loops are threaded by the BDC rods from above and below 2D layers so as to form 2D → 3D polyrotaxane and polycatenane structures. In 4, the CdII ions are linked by L2 ligands to generate 1D double chain ribbons with Cd2(L2)2 loops, which are further connected by the BDC linkers to form a 3D framework. Two identical 3D frameworks interpenetrate each other in a twofold mode, giving rise to a polyrotaxane and polycatenane array, which is relative limited. The diverse structures of complexes 1–4 demonstrate that the tri-pyridyl–bis-amide ligands and the central metals have significant effect on the final structures. The thermal stability and fluorescent properties of complexes 1–4 have been investigated. In addition, the title complexes exhibit photocatalytic activity for dye methylene blue degradation under UV light.

A series of metal–organic coordination polymers, namely, {[Cu3(4-bpah)4(1,3,5-BTC)2]·8H2O}n (1), {[Cu3(4-bpah)3(1,2-BDC)3(H2O)2]·4H2O}n (2), {[Cu(4-bpah)(1,3-BDC)(H2O)]}n (3), {[Co(4-bpah)(1,3-BDC)(H2O)]}n (4), {[Ni(4-bpah)(1,3-BDC)(H2O)]}n (5), {[Zn(4-bpah)(1,3-BDC)(H2O)]}n (6), {[Cd(4-bpah)(1,3-BDC)]}n (7), {[Cd(3-bpah)(1,3-BDC)]·H2O}n (8), {[Cu2(3-bpah)(1,3-BDC)2]·H2O}n (9), where 4-bpah = N,N′-bis(4-pyridinecarboxamide)-1,2-cyclohexane, 3-bpah = N,N′-bis(3-pyridinecarboxamide)-1,2-cyclohexane, 1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid, 1,2-H2BDC = 1,2-benzenedicarboxylic acid, 1,3-H2BDC = 1,3-benzenedicarboxylic acid, have been synthesized under hydrothermal conditions. The structures of 1–9 have been determined by single crystal X-ray diffraction analyses and further characterized by infrared spectroscopy (IR), elemental analyses, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). Complex 1 displays a 2D (42·83·10)(43·62·8)4(4)2 topological network. Complex 2 shows a 2D (3·4·5·62·7)2(3·42·52·7) topological framework that contains tri-flexural and left-hand helix chains. Complexes 3–6 reveal a similar 2D sql network with (44·62) topology. Complexes 7 and 8 show two different 2D double-layer structures with (42·6)(43·6·84·102)(4) and (42·6·86·12)(42·6)(8) topology, respectively. Complex 9 exhibits a new 3D 3-nodal topology with the Schlafli symbol (4·62)2(42·64)2(42·68·82·103). The successful construction of complexes 1–9 implies that using semi-rigid bis-pyridyl-bis-amide ligands can obtain various architectures with small voids. The effect of the isomeric semi-rigid bis-pyridyl-bis-amide ligands and the three aromatic polycarboxylates, as well as the central metal ions on the formation and structures of the title coordination polymers have been discussed. The fluorescent and photocatalytic properties of complexes 1–9 have also been investigated.

To probe the coordination approach of pyridazine and pyrazine ligands, five new complexes of [CuII2L2Cl2] (1), [CuII(L-H)(NO3)(H2O)2](NO3)(H2O) (2), {[CuII(L-H)(H2O)](ClO4)2(H2O)}n (3), [CuII2L2(OH)](NO3)(H2O)2 (4), [CuII2L2(OH)](ClO4) (5) based on Schiff base ligand (E)-3-chloro-6-[2-(pyrazin-2-ylmethylene)hydrazinyl]pyridazine (HL) bearing pyridazinyl and pyrazinyl groups have been synthesized and characterized by IR spectra, elemental analyses, the bond valence sum (BVS) analyses, powder X-ray diffraction (PXRD) analyses, X-ray single crystal diffraction and density function theory calculations. The structures of 1, 2 and 3 suggest that the second nitrogen donors of the pyrazinyl unit can link with other metal ions to construct a higher dimensional architecture by the reaction of HL with Cu(ClO4)2 [CuCl2 for 1, Cu(NO3)2 for 2 and Cu(ClO4)2 for 3]. The structures of 4 and 5 indicate that additional donor units of the pyridazinyl chromophore can bind multiple metal ions to form a multi-metallic cluster, when the protons of the hydrazone backbones are abstracted in the presence of triethylamine to strengthen the coordination behavior of the second nitrogen atom. However, for 1, the protons of the hydrazone backbone are lost with or without triethylamine and the additional nitrogen atoms of the pyrazinyl and pyridazinyl groups are not found to connect to other metal ions, which can probably be assigned to the strong coupling effect of chlorine ions. Magnetic measurements display weak antiferromagnetic coupling between the copper(II) ions in 1 and 5, and ferromagnetic coupling in 3. In addition, the antioxidant activities of HL and 1–5 were also studied.

Four new coordination polymers [Co(bbbm)(1,3-BDC)]·H2O (1), [Co3(bbbm)4(SIP)2(H2O)2]·2H2O (2), [Cd3(bbbm)3(SIP)2(H2O)4]·2H2O (3) and [Cd(bbbm)(NIP)] (4) (bbbm = 1,1-(1,4-butanediyl)bis-1H-benzimidazole, 1,3-H2BDC = 1,3-benzenedicarboxylic acid, H3SIP = 5-sulfoisophthalic acid and H2NIP = 5-nitroisophthalic acid) have been hydrothermally synthesized and structurally characterized. Complex 1 possesses a two-dimensional (2D) (4,4) network structure. CoII ions are connected by the 1,3-BDC anions to form one-dimensional (1D) linear chains, which are extended into 2D layers by the bbbm ligands. 2 shows a three-dimensional (3D) (3,4,5)-connected framework with a (6.82)2(69.8)2(86) topology. In complex 2, Co-SIP ladder-like chains are linked by the bbbm ligands to generate a 3D framework. 3 exhibits a 3D (3,3,4,4,4)-connected framework with a novel (3.6.73.8)(3.6.7)(3.62.73)(6.72)(6.74.10) topology. CdII ions are connected by SIP anions to form 2D layers containing 12-membered macrocycle, which are further connected by the bbbm linkers to form a 3D framework. 4 displays a 3D 8-connected framework with a (424.64) topology. In complex 4, binuclear cadmium clusters are extended into 3D structure by the bbbm ligands and NIP anions. The substituent group of polycarboxylates plays an important role in the assembly and structures of title complexes. The electrochemical properties of 1 and 2, photoluminescent properties of 3 and 4 have been reported.

An unusual (4,6,6)-connected high dimensional organopolymolybdate polymer by 1,4-bis(1,2,4-triazol-1-yl)butane coordinating directly to a molybdenum atom has been obtained under hydrothermal condition, which exhibits a self-penetrating framework with (44·5·6)(45·54·66)(48·52·65) topology assembled from 2D self-threading skeleton.