Two metal–organic frameworks (MOFs), namely, [Ni(DTP)(H2O)]n (I) and [Cd2(DTP)2(bibp)1.5]n (II) (H2DPT = 4′-(4-(3,5-dicarboxylphenoxy) phenyl)-4,2′:6′,4″-terpyridine; bibp = 1,3-di(1H-imidazol-1-yl)propane), that present structural diversity were solvothermally prepared. Single-crystal X-ray diffraction analysis indicates that they consist of {NiN2O4} building units (for I) and {CdO4N2} and {CdO3N3} building units (for II), which are further linked by multicarboxylate H2DPT to construct microporous three-dimensional frameworks. The remarkable character of these frameworks is that coordination polymer II demonstrates highly selective and sensitive bifunctional luminescent sensor toward nitrobenzene and Cu2+ ion. The fluorescence quenching mechanism of II caused by nitrobenzene is ascribed to electron transfer from electron-rich (II) to electron-deficient nitrobenzene. The result was also evidenced by the density functional theory. Furthermore, anti-ferromagnetic as well as electrochemical characters of Ni-MOF (I) were also investigated in this paper.Keywords: fluorescent recognition; luminescence quenching; metal−organic framework; sensor; solvothermal synthesis;

Two novel coordination polymers, namely {[Co(Ttac)0.5(1,4-Bib)(H2O)] · H2O}n (I) and {[La(HTtac)2(2H2O)] · H2O}n (II) (H4Ttac = 4,5-di(3'-carboxylphenyl)-phthalic acid, 1,4-Bib = 1,4-bis(1-imidazoly) benzene), have been designed and successfully prepared via hydrothermal process, and characterized by elemental analyses, IR spectroscopy, and single crystal X-ray diffraction (CIF files CCDC nos. 1039298 (I), 1039300 (II)). Structural analysis reveals that the H4Ttac ligands adopt different coordination modes in the as-synthesized I and II, and thus give rise to the targeted coordination polymers with different configurations. It is worth mentioning that, coordination polymer I is assembled from low-dimensional structures into three-dimensional (3D) via π···π stacking interactions, while three-dimensional coordination polymer II is formed by covalent bonds. Luminescent properties of coordination polymer II have been studied at ambient temperature. Significantly, luminescent measurement indicates that coordination polymer II may be acted as potential luminescent recognition sensors towards Cu2+ and Mn2+ ions.

•Coordination polymers I–II have been synthesized together with three auxiliary ligands.•I–II are assembled form low-dimensional structures into three-dimensional frameworks.•I and II display highly selective recognition towards Cu2+.Two novel coordination polymers, namely, {[Cd(pdpy)(H2O)2]·SUL·(H2O)0.5}n (I) and {[Cd(pdpy)(PTA)]·H2O}n (II) (pdpy = piperazine-1,4-diylbis(pyridine-4-ylmethanone), PTA = p-phthalic acid and SUL = 5-sulphosalicylic acid) have been designed and successfully prepared under hydro-thermal conditions and characterized by elemental analyses, IR spectroscopy, and single crystal X-ray diffraction. Structural analysis indicates that the pdpy ligands adopt three different coordination modes in the as-synthesized I–II, and thus result in diversity of the targeted coordination polymers. It is worth mentioning that, based on the hydrogen bonding, I–II are assembled from two-dimensional (2D) structures into three-dimensional (3D) frameworks. Luminescent properties of I and II have been studied at ambient temperature. Significantly, both I and II show highly selective response to Cu2+ cations through luminescence quenching effects, which may make them promising luminescent selective recognition sensors for Cu2+.Two novel three-dimensional coordination polymers with highly selective luminescent recognition of Cu2+ have been prepared based on low-dimensional architectures through intermolecular forces under hydrothermal conditions and characterized.

The compound [Gd2(PZDA)3(H2O)]n (I), where H2PZDA = 2,3-pyrazinedicarboxylic acid, was synthesized under hydrothermal conditions and characterized by elemental analysis, infrared spectrometry, thermogravimetric analysis and single crystal X-ray diffraction (CIF file CCDC no. 848802). In I, Gd(III) centers adopt eight-coordinated and nine-coordinated modes to construct distorted triangular dodecahedral and tricapped trigonal prism configurations, respectively. Three-dimensional (3D) structure of the compound is formed through C-H⋯π interactions and π-π stacking. Measurement of the luminescent property at room temperature shows that the as-synthesized compound presents good selectivity towards Pb2+ ion, suggesting that it may be promising potential as selective luminescent probes of Pb2+ ion.

•Seven lanthanide coordination polymers are isomorphous.•The framework of Ln2O2(OCO)2 or Tb2(OCO)4 act as the subunits in the construction of I–VII.•I–VII are assembled into 3D porous architectures via coordinate covalent bonds, hydrogen bonds and C–H⋯π interactions.•Structure comparison of the coordination polymers suggests that lanthanide contraction effect exists.•I and III present antiferromagnetic behaviors and luminescent studies suggest I displays good selectivity towards Ca2+ and Cd2+.Seven lanthanide coordination polymers, namely, {[Ln(BDOA)1.5(H2O)]·H2O}n (Ln = Ce(I), Pr(II), Nd(III), Sm(IV), Eu(V), Gd(VI), and Tb(VII), H2BDOA = benzene-1,4-dioxydiacetic acid), have been synthesized through hydrothermal reactions of lanthanide nitrate with H2BDOA ligands and characterized by elemental analysis, infrared spectroscopy and single crystal X-ray diffraction. Findings indicate that I–VI are isomorphous and isostructural, containing the subunit of cavate 10-membered cages (Ln2O2(OCO)2), while VII possesses the subunit of cavate 14-membered cages (Tb2(OCO)4), based on which to assemble into three-dimensional porous architectures via BDOA2− ligands, hydrogen bonds and C–H⋯π interactions. I and III present antiferromagnetic behaviors and lanthanide contraction effect exists in I–VI. Luminescent studies suggest the typical intense emissions of Ln(III) ions occur in the visible region and therefore the coordination polymers display good selectivity towards some certain metal ions such as Ca2+ and Cd2+, showing promising potential as selective luminescent probes of these metal ions.In coordination polymer I, the adjacent two crystallographically equivalent Ce(III) ions are bridged by two oxygen atoms in μ2-η2 fashion and two carboxy groups in μ1-η1:η1 fashion to form a cavate 10-membered cage (Ce2O2(OCO)2) which serves as the subunit, based on which to generate a 3D porous architecture via BDOA2− ligands, hydrogen bonds and C–H⋯π interactions.

•3D network of I is constructed via μ2-Cl bridges, hydrogen bonds and C–H⋯π interactions.•2D layers of II and III are formed by the helical chains through hydrogen bonds.•Luminescencent peaks of I–III appear in the visible and near-infrared regions.•III presents antiferromagnetic property.Three novel transition metal coordination polymers including [Cd2(Na2PPDA)2Cl4]n (I), [Zn(Na2PPDA)(ClO4)2·4H2O]n (II) and [Ni(Na2PPDA)(ClO4)2·4H2O]n (III) were prepared under hydrothermal conditions based on (2,3-f)-pyrazino(1,10)phenanthroline-2,3-dicarboxylic acid sodium salt (Na2PPDA) and characterized by elemental analysis, infrared spectrometry and single crystal X-ray diffraction. The outstanding structural feature of I is that four cadmium atoms are linked into a zigzag-shaped polymeric chain in the sequence of Cd–(Cl)2–Cd–(Cl)2–Cd–(Cl)2–Cd by three μ2-Cl bridges. Findings indicate that I displays a three-dimensional (3D) network constructed via hydrogen bonds and C–H⋯π interactions. Both coordination polymers of II and III present isomorphous and isostructural characters, in which the adjacent metal centers in the same chain connected up and down through hydrogen bonds (generated through μ2-ClO4− anions) to construct the left- and right-handed helical chains which are further interconnected by hydrogen bonds, thereby affording a two-dimensional (2D) layer. Moreover, thermogravimetric (TG) analyses, the magnetic and luminescent properties of as-synthesized coordination polymers were also investigated.Findings indicate that 1D zigzag-shaped chains based on Cd4Cl6 units are linked into 2D layers through hydrogen bonds and C–H⋯π interactions in different directions. The adjacent 2D layers extending in different directions are interconnected into 3D network through weak interactions above-mentioned in clinker-built fashion.

•The complexes possess three-dimensional frameworks which are assembled through hydrogen bonds and π–π interactions.•{[Ce2(PDA)2(H2O)5SO4]·2H2O}n presents one-dimensional nanosized cavities, where the guest water dwelled.•Luminescence of the complexes in methanol display selectivities to Zn2+, Hg+, Pb2+ Mn2+ and Cd2+ or Cu2+ ions.3D coordination polymers of {[Ce2(PDA)3(H2O)3]*0.25(H2O)}n and {[Ce2(PDA)(HPDA)(H2O)5SO4]*2H2O}n, (H2PDA = pyridine-2,6-dicarboxylic acid,) have been prepared under hydrothermal conditions and characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. In the dihydrate polymer the SO42−- anions serve as bridges between 1D wavelike chains and the adjacent parallel pyridine rings are connected through π–π interactions. The striking feature of the dihydrate polymer is that 1D nanosized cavities are observed, which house guest water molecules. Weak interaction exists between Ce(IV) center and S atom(Ce…S) due to the connection of chelate SO42− anion. A magnetic study of the dihydrate polymer confirms that it presents antiferromagnetism. Thermogravimetric and differential thermogravimetric analyses reveal that both polyers are stable at high temperature. Luminescent emissions of complexes demonstrate that they display selectivities towards Zn2+, Hg+, Pb2+ Mn2+ and Cd2+ or Cu2+ ions.The coordination polymer is connected between the adjacent building block of [Ce2(PDA)2(H2O)5SO4]·2H2O through carboxylate bridges (O–C–O). An infinite 1D (Ce–O2–Ce–OCO–Ce–O2–Ce)∞ wavelike chain motif along the a   axis is formed through the bridges of carboxylate (O–C–O) and double oxygen alternately. Furthermore, the adjacent 1D chains are jointed through SO42− anions from both above and below to construct a highly ordered 2D layer along the c axis. Considering the sum of the van der Waals radii of Ce and S atoms, it is reasonable to assume that there is certain interaction between Ce and S atoms.

Three novel coordination polymers including {[Mn2(bptc)2(phen)4]·2H2O}∞ (I), [Zn2(bptc)4·(bpy)2·H2O]∞ (II), and {[Zn2(bptc)4·(bpy)2·H2O] ⊃ bpy}∞ (III) (bptc = 3,3′,4,4′-benzophenone-tetracarboxylate, bpy = 4,4′-bipyridine, phen = 1,10-phenanthroline) were prepared under hydrothermal conditions and characterized by elemental analysis, infrared spectrometry, and single crystal X-ray diffraction. Moreover, the thermal stability of as-synthesized coordination polymers was evaluated by thermogravimetric analysis; and their magnetic and luminescent properties were also investigated. Findings indicate that coordination polymer I displays a three-dimensional (3D) network constructed via π–π interactions of the building block {[Mn2(bptc)2(phen)4]·2H2O}. Besides, Zn(1) and Zn(2) centers in coordination polymer II are four-coordinated and six-coordinated, respectively, thereby affording two-dimensional (2D) planar sheet and 3D porous frameworks that are interlinked through identical linkers of four-coordinated motif (COO–Zn–COO). As-synthesized coordination polymer III contains a 3D framework similar to that of II, but the cavities in III are occupied by uncoordinated bpy guest molecules. Moreover, as-synthesized coordination polymer I presents antiferromagnetic coupling through the (O2C–C–C–CO2)2 bridges, and II displays selectivity towards Hg+ ion in terms of the luminescent emission.

A series of 3D isomorphous and isostructural coordination polymers, namely, {[Ln4(PDA)6(H2O)6]·H2O}∞ (Ln = La, Nd, Sm and Gd; corresponding as-synthesized products are denoted as 1, 2, 3, and 4, respectively; PDA2− = pyridine-2,6-dicarboxylate anion), were synthesized under hydrothermal conditions and characterized by means of elemental analyses, infrared spectrometry, thermal analysis and single crystal X-ray diffraction. In the meantime, the thermal decomposition kinetics of the as-synthesized complexes was investigated under non-isothermal conditions using the Achar differential method and the Coats–Redfern integral method. The room-temperature luminescent properties of the metal-organic frameworks (MOFs) of the lanthanide coordination polymers were measured. It has been found that Ln(III) centers in the complexes adopt eight-coordinated and nine-coordinated modes with N1O7 and N2O7 donors to construct distorted triangular dodecahedral and tricapped trigonal prism configurations, respectively. Based on the building block of tetranuclear homometallic La4C4O8 unit (16-membered ring), lanthanide coordination polymers 1–4 are connected into highly ordered two-dimensional corrugated layers via O—C—O linkers and further assembled into 3D architectures through hydrogen bonds. Besides, lanthanide contraction effect exists in as-synthesized coordination polymers; and the lanthanide coordination polymers possess good selectivity toward metal ions such as Mg2+, Cu2+ and Pb2+, showing promising potential as selective luminescent probes of those metal ions.Highlights► A series of isomorphous and isostructural coordination polymers have been synthesized. ► The complexes are assembled into 3D frameworks through OCO bridges and hydrogen bonds. ► The complexes may be potential luminescent probes toward some metal ions. ► Thermal analyses and thermal decomposition kinetic equations have been investigated.

Pyridine-2,6-dicarboxylic acid (H2PDA) was used for the synthesis of two MOFs polymers {[Ln2(PDA)3(H2O)3]·H2O}n (Ln = Pr(1) and Eu(2)) with Pr(NO3)3·6H2O and Eu(NO3)3·6H2O under hydrothermal conditions and characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. Both compounds crystallize in monoclinic system, space group P 21/c. Both of the two compounds are isomorphous and isostructural. Different rings exist in the title compounds and form the 2D metal–organic framework. The 3D structures are constructed through covalent bonds and hydrogen bonds. The thermal decompositions have been predicted with the help of thermal analyses (TG and DTG). Furthermore, the luminescent properties of 2 were studied in the solution of DMF at room temperature.Highlights► Two MOFs polymers {[Ln2(PDA)3(H2O)3]·H2O}n (Ln = Pr(1) and Eu(2)) were synthesized and characterized. ► Both the 3D frameworks are assembled from the structure units containing three types of rings via hydrogen bond and OCO bridges. ► The thermal decompositions of 1 have been predicted with the help of thermal analyses and emission spectra of 2 have been identified.

Two kinds of 3D coordination polymers, namely, {[La2(PDA)3(H2O)4]·H2O}∞ (I) and {[Pr2(PDA)3(H2O)3]·H2O}∞ (II) have been synthesized under hydrothermal conditions and characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. In complex I, La(III) ions are nine-coordinated and ten-coordinated and have N1O8 or N1O9 polyhedral units connecting to the PDA2− anions forming tricapped trigonal prism and double-capped cubic antiprism geometries, respectively. Two types of ring motifs as building blocks constructed by La8C2O10 (20-membered ring) and La4C2O6 (12-membered ring) are connected alternately into a highly ordered 2D sheet and further assembled into a nanoporous 3D coordination polymer with parallel channels. In complex II, Pr(III) ions are eight-coordinated and nine-coordinated and have N1O7 or N2O7 polyhedral units connecting to the PDA2− anions forming trigonal dodecahedron and tricapped trigonal prism configurations, respectively. The tetranuclear homometallic motifs formed by Pr4C4O8 unit (16-membered ring), acting as the building blocks, are constructed into a 3D coordination polymer. Luminescent emissions of the lanthanide-based MOF of complexes I and II have been measured in the solution of DMF at room temperature, which reveal that they presenting ion-selective characters toward certain metals, such as Pb2+, Ca2+ and Cu2+ or Cd2+ ions.Highlights► Two kinds of coordination polymers I and II based on the building blocks of La8C2O10 and La4C2O6 or Pr4C4O8 motifs have been synthesized and characterized. ►Two types of 1D nanochannels tier up alternatively in parallel manner in the polymer I. ►The luminescent experiments show that complexes I and II present particular selectivity toward Pb2+ and Ca2+ or Cd2+ ions.

Two novel coordination polymers, namely, {[Ln2(PDA)(HPDA) (H2O)4ClSO4]·2H2O}n (Ln = La(III) and Ce(III) for complexes I and II, respectively) were synthesized through the reaction between pyridine-2,6-dicarboxylic acid (H2PDA) and La(NO3)3·6H2O and Ce2(SO4)3·8H2O under hydrothermal conditions. Both of these polymers possess 1D infinite nanosized cavities embedding guest water molecules. The complexes were characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. Two compounds crystallize in orthorhombic system, space group Pna2(1). Both of the complexes exhibit 3D metal–organic framework structure, where SO42− anions play as the bridge between 1D wavelike chains and the adjacent parallel pyridine rings were arranged through π–π interactions. The bi-bidentate coordination mode of SO42− anion was observed. Luminescent emissions of complex I were measured in the solution of DMF at room temperature. In addition, the luminescent emissions of complex I showed certain selectivity among some metal ions.Highlights► New coordination polymers {[Ln2(PDA)(HPDA) (H2O)4ClSO4]·2H2O}n (Ln = La(III) and Ce(III) have been synthesized. ► 3D framework possessing 1D nanosized cavities with guest water molecules embedded. ► Luminescent emission of complex I displays selectivity toward Ag+, Hg2+ and K+.

The coordination polymer [Nd2(pzdc)3(H2O)]n·nH2O (complex I) with three-dimensional framework has been prepared by hydrothermal synthesis of 2,3-pyrazinedicarboxylic acid (pzdc) and neodymium nitrate and characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. The complex crystallizes in monoclinic system, space group P2(1)/c. Every Nd(III) atom in the coordination polymer is nine-coordinated with different coordination environments. The pzdc ligands coordinate to the central Nd(III) atoms in bridging tetradentate, hexadentate, or heptadentate modes. The thermal decomposition of the complex has been predicted with the help of thermal analyses (TG, DTG and DTA). Complex I exhibits luminescent emissions bands in the solid state at room temperature. The isomorphous complex [Nd4(pzdc)6(H2O)2]n·3nH2O (complex II) has also been prepared by hydrothermal reaction under different conditions. Luminescent emission of complex I display selectivity for some heavy metal ions.Highlights► New coordination polymers [Nd2(pzdc)3(H2O)]n·nH2O and [Nd4(pzdc)6(H2O)2]n·3nH2O have been synthesized. ► The two isomorphous complexes may be prepared at different temperatures. ► Luminescent emission of complex I displays selectivity for heavy metal ions such as Pb2+, Hg2+ and so on.

•Three-dimensional coordination polymers I, II and III have been prepared and characterized.•III presents high selectivity and sensing for Pb2+ ion over mixed metal ions.•Coordination polymer I presents antiferromagnetism.•Lanthanide contraction effect exists in these coordination polymers.Three novel coordination polymers, namely, {[Pr(TTTPC)·(H2O)2]·2Cl·NO3·4H2O}n (I), {[Gd(TTTPC)·(H2O)2]·2Cl·NO3·4H2O}n (II) and {[Yb(TTTPC)·(H2O)2]·3Cl·NO3·0.5DMA·6H2O}n (III) were synthesized in conventional aqueous solutions with H3TTTPC ligands (H3TTTPC = 1,1′,1″-(2,4,6-trimethylbenzene-1,3,5-triyl(methylene))-tris(pyridine-4-carboxylic acid), DMA = N,N-dimethylacetamide) and characterized by infrared spectrometry and single crystal X-ray diffraction. Experimental results show that these MOFs are isomorphous and isostructural, containing the unit of cavate 14-membered cages (Pr2(OCO)4), based on which to generate a one-dimensional (1D) infinite linear metallic chain through the linkage of two COO− groups that are further interlinked reciprocally to polymerize into three-dimensional (3D) porous frameworks. Coordination polymer III shows remarkable selectivity toward Pb2+ and it can be considered as potential selective luminescent probes for Pb2+ ion. Additionally, magnetic analysis indicates coordination polymer I presents antiferromagnetism. Besides, lanthanide contraction effect exists in as-synthesized coordination polymers.Three novel coordination polymers, namely, {[Pr(TTTPC)·(H2O)2]·2Cl·NO3·4H2O}n (I), {[Gd(TTTPC)·(H2O)2]·2Cl·NO3·4H2O}n (II) and {[Yb(TTTPC)·(H2O)2]·3Cl·NO3·0.5DMA·6H2O}n (III) were synthesized under hydrothermal conditions and characterized. Furthermore, their luminescent recognition and magnetic properties were investigated.