Two-dimensional Coordination Polymer Research Articles

Guest-Induced Reversible Single-Crystal-to-Single-Crystal Transformation Involving Displacement of 2D Layers and Spin Crossover Behavior Change in a Hofmann-Type Coordination Polymer.

A novel two-dimensional (2D) Hofmann-type coordination polymer, {FeII(PyHbim)2[Pd(CN)4]}·2CH3OH [1·2CH3OH, PyHbim = 2-(4-pyridyl)benzimidazole], has been synthesized, which can undergo a spontaneous guest exchange, transforming to 1·2H2O in a single-crystal-to-single-crystal (SCSC) manner, shifting from orthorhombic Cmmm to monoclinic C2/m involving the displacement of 2D layers. The solvent-induced SCSC transformation process was reversible and verified through powder X-ray diffraction (PXRD) and single-crystal X-ray crystallography analyses. Both 1·2CH3OH and 1·2H2O exhibit complete and abrupt spin crossover (SCO) behaviors in two steps, while their SCO temperature ranges drastically shift by ca.100 K, spanning room temperature, owing to different intermolecular interactions resulting from diverse interlayer packing manners and host-guest interactions. Besides, a structural phase transition is observed in 1·2CH3OH, contributing to the two-step spin transition.

Highly Specific Sulfadiazine Detection Using a Two-Dimensional Europium-Organic Coordination Polymer.

Sulfadiazine (SFZ) is an inexpensive large-consumption antibiotic used for treat bacterial infections but an excess of residues in food can be harmful. Fast and specific luminescence detection of SFZ is highly challenging because of the interference of structurally similar antibiotics. In this work, we develop a two-dimensional europium-organic coordination polymer with excellent luminescence and water stability for highly specific detection of SFZ in the range of 0-0.2 mM. Structural analysis shows that the high stability of coordination polymer is due to the high coordination number of europium ion and the special chelating coordination structure of ligand. The experiment results revealed that the high selectivity and effectively luminescence quenched behaviour of coordination polymer toward SFZ is caused by highly efficient inner filter effect.

A water stable europium coordination polymer based on mixed organic ligands as a luminescence sensor for the detection of an anthrax biomarker

The development of luminescence sensors capable of detecting anthrax biomarkers is crucial for preventing anthrax. In this study, a two-dimensional europium coordination polymer [Eu(dlba)(phen)·2(H2O)]n (CP-1) was prepared based on a rigid 1,10-phenanthroline (phen) and a flexible 2-(3,5-dicarboxybenzyloxy) benzoic acid (H3dlba) under the hydrothermal conditions. The CP-1 was characterized by powder X-ray diffraction, elemental analysis, thermogravimetric analysis, infrared spectroscopy, and single crystal X-ray diffraction. The CP-1 exhibits excellent water stability and thermal stability. Luminescence experiments demonstrated a high luminescence quenching efficiency (98.1 %) upon addition of the anthrax biomarker dipicolinic acid (DPA). Additionally, the sensor shows good sensitivity and a rapid response time of 30 s. The detection limit is as low as 0.12 µM, which is much lower than the infection dose of spores (60 µM). The sensor has a recovery rate of 95–105 % when tested on actual samples, indicating its potential for practical applications. The luminescence quenching effect may be due to the competitive absorption of DPA, which affects the efficiency of energy transfer from the ligands to the europium ions.

Facile synthesis of amorphous/crystalline Ni-Fe thiophenedicarboxylate coordination polymer nanobelts for efficient water oxidation

The oxygen evolution reaction (OER) is a complex four-electron transfer process that poses a significant challenge to the efficient production of hydrogen through water splitting. However, developing non-noble metal electrocatalyst with excellent OER performance is still a big challenge. Herein, we propose a new strategy for the in-situ growth of two-dimensional amorphous/crystalline thiophene-based Ni-Fe metal–organic frameworks (MOFs) using Ni-Fe foam (NFF) as metal source and current collector, and thiophene-2,5-dicarboxylic acid (TDC) as corrosion agent and ligand. TDC was ionized at high temperature to produce H+ ions that etch NFF to release Ni2+ and Fe2+ ions, which were coordinated with TDC to in situ synthesize two-dimensional Ni-Fe thiophenedicarboxylate coordination polymer (NiFe-TDC) nanobelts on NFF. The unique structure and synergistic effect of Ni and Fe ions of NiFe-TDC0.05 result in the excellent OER performance with an overpotential of 224 and 256 mV at current densities of 10 and 100 mA cm−2, respectively, and it can run stably for 100 h at a current density of 100 mA cm−2, indicating the outstanding stability. Furthermore, NiFe-TDC0.05 remains the excellent OER performance with an extremely low potential of 196 and 271 mV at current densities of 10 and 100 mA cm−2 in seawater with 1 mol L-1 (M) KOH, respectively. The assembled NiFe-TDC0.05 || Pt/C water electrolysis cell achieves a current density of 100 mA cm−2 at a low voltage of 1.78 V. The work provides a new method to prepare two dimensional MOFs for efficient water oxidation.

Three multifunctional two-dimensional coordination polymers based on 1-(3-carboxybenzyl)-4,4′-bipyridinium ligand

By utilizing the carboxybenzyl viologen ligand 1-(3-carboxybenzyl)-4,4′-bipyridinium chloride (HBcbpy·Cl), 1,3,5-benzenetricarboxylic acid (H3BTC) and varying different metal ions, three new coordination polymers [Cd(Bcbpy)(HBTC)(H2O)·2H2O]n (1), [Zn(Bcbpy)(HBTC)(H2O)·2H2O]n (2) and [Co2(Bcbpy)2(HBTC)2(H2O)2·4H2O]n (3) have been synthesized and structurally characterized. Compounds 1 and 2 have identical two-dimensional (2D) coordination layered structure, while compound 3 features 2D+2D→2D structure. It is interesting that compounds 1 and 2 exhibit electron transfer photochromism, while compound 3 displays hydrochromism through dehydration. At the same time, considering the high stability and fast photo-response, the photo-modulated fluorescence and the inkless erasable printing capability are investigated.

A two-dimensional coordination polymer bearing an Evans-Showell-type polyoxometalate: Synthesis, structure and biological insight†

An Evans-Showell-type polyoxometalate (POM) based coordination polymer (CP), [H2(Co2Mo10H4O38)2(Co3(L)3(HL)2(H2O)6)(HL)2]·14H2O (1), {L = 4,4′-bipyridine}, was synthesized under hydrothermal conditions and structurally characterized by infrared spectroscopy (IR), elemental analysis, powder X-ray diffraction (PXRD), diffuse reflectance spectroscopy (DRS) and single crystal X-ray diffraction methods. In 1, two [Co2Mo10H4O38]6− POMs are joined together via two Co-O interactions to form a dimer which is centrosymmetric. Here, the dimers act as repeating units and are expanded by another crystallographically independent Co ion in the structure. Binding of the cations to the O atoms of the POM and the N atoms of organic ligand resulted in the formation of a 2D CP structure. Compound 1 is the first example of an inorganic-organic polymer architecture constructed from Evans-Showell-type POM in which Co cations act as metal nodes. The topology of 1 can be rationalized as a 2D square lattice (sql) coordination network with point symbol {44.62} in which [Co2Mo10H4O38]6− and 4,4′-bipyridine units act as linkers and the Co cations as nodes. The cytotoxicity effects of the POM were evaluated on the cancer CT26 and normal L929 cell lines by an MTT assay from which an IC50 value of cancer CT26 cells of approximately 366 ppm was obtained, but normal L929 cells did not show significant toxicity.

Investigation on fluorescent sensing properties of Cd(II)-coordination polymers synthesized by nitrogen-containing carboxylic acid ligand

In this study, two-dimensional (2D) cadmium-based coordination polymer (CP) (Cd-1, [Cd4L8]n) and one-dimensional (1D) cadmium-based CP (Cd-2, [CdL(H2O)(NO3)·H2O]n) have been obtained by mixing 1-(4-benzoic acid)-3-(pyrazinyl)-1H-1,2,4-triazole (HL) as organic ligand and CdCO3 as a source of metal ions in hydrothermal/solvent-thermal reaction. The structures and properties of two examples of Cd(II) CPs were characterized and analyzed. The results from infrared spectroscopy, thermogravimetric analysis, and X-ray single-crystal diffraction analysis indicated that the CPs have a stable framework structure and better thermal stability. In addition, in the study of fluorescence properties, two Cd(II)-CPs were found to have high sensitivity to the specific recognition of Fe3+, CrO42− and Cr2O72− ions in metal nitrate and anionic aqueous solutions, and the stability and recyclability of which were further demonstrated through cycling tests, which are expected to be used for the development of the new Cd(II)-CPs and to be an excellent fluorescent probe material.

Fabrication of Substituent-Regulated Two-Dimensional Copper-Based Coordination Polymers as Urease Inhibitors

Fabrication of Substituent-Regulated Two-Dimensional Copper-Based Coordination Polymers as Urease Inhibitors

Isolation of a Cd-Based Coordination Polymer Containing Mixed Ligands: Time- and Temperature-Dependent Synthesis, Sulfonamide Antibiotics Detection, and Schottky Diode Fabrication.

In this study, we present a new cadmium(II)-based two-dimensional coordination polymer [Cd (L)(NA)(H2O)] (L = Iminol form of N-nicotinoyl glycinate, NA = nicotinate), 1, containing two linkers generated from N-nicotinoyl glycine. A comprehensive investigation was carried out during the synthesis of the coordination polymers by varying the reaction time interval and temperature, and it revealed the formation of three distinct phases, of which two phases were previously reported and one was a new compound (1). The structure of compound 1 was determined by single-crystal X-ray diffraction, and it shows a corrugated layer structure with hydrogen bond interactions leading to three-dimensional supramolecular arrangements. Compound 1 exhibited strong emission at 420 nm when excited at 260 nm in an aqueous medium. The emission behavior of this compound was used for the detection of various sulfonamide antibiotics, sulfadiazine, sulfamethazine, sulfachloropyridazine, sulfameter, sulfaquinoxaline, and sulfathiazole, in the presence of common water pollutants. The luminescence quenching response of compound 1 to sulfonamide antibiotics was significant, ranging from 81 to 94%, and the detection sensitivity reached parts per billion (ppb) levels (226-726 ppb). Compound 1 also used for the fabrication of Schottky diode devices with a barrier height of 0.86 eV along with an excellent ideality factor of 1.24.

Solvent control of dimensionality in titanium aryloxide coordination polymers prepared from 4,4′-bis(hydroxyphenyl)sulfide

The crystal and molecular structures of three covalent metal–organic network (CMON) materials synthesized from titanium (IV) isopropoxide and the Bisphenol-A analog 4,4′-bis(hydroxyphenyl)sulfide in three different solvents have been determined. The structures of the one-dimensional chain coordination polymer [trans-Ti(μ-O:O’-OC6H4SC6H4O)2(C5H5N)2]n (1) obtained from pyridine and the two-dimensional sheet coordination polymer {[Ti2(μ-O:O’-OC6H4SC6H4O)2(μ2O:κO’-OC6H4SC6H4O)2(C4H8O)2]∙(C4H8O)y}n (2) from tetrahydrofuran both contain octahedral titanium (IV) coordination geometries, whereas the doubly interpenetrated three-dimensional coordination network [Ti2(μ-O:O’-OC6H4SC6H4O)2(μ2O:κO′-OC6H4SC6H4O)2]n (3) synthesized from benzene contains trigonal bipyramidal titanium (IV). Each material has been characterized by single crystal and powder X-ray diffraction, elemental analysis, and by 1H NMR quench when it contains more than one organic component.

A Eu coordination polymer sensor for the detection of tartrazine, folic acid, and amino acids

In this work, 3-(2,4-dicarboxyphenyl)-6-carboxypyridine (H2ppda) and 4-(4-carboxyphenyl)benzoic acid (H2bpdc) were selected to synthesize a two-dimensional layered coordination polymer, [Eu(ppda)(bpdc)0.5(C2H5OH)(H2O)]n (Eu-1). Eu-1 is further hydrogen-bonded to construct a three-dimensional supramolecular structure. It has found that Eu-1 can be used as an excellent fluorescence sensor for the determination of food additives, such as tartrazine (TA), folic acid (FA), arginine (Arg), and lysine (Lys). Eu-1 showed high sensitivity, selectivity, recyclability, and anti-interference for the detection of TA, FA, Arg, and Lys in aqueous solution. The limits of detection TA, FA, Arg, and Lys are 9.87 × 10-8 M, 3.28 × 10−8 M, 2.20 × 10-6 M, and 9.46 × 10-7 M, respectively. Notably, it is the first example of luminescent coordination polymer to identify TA in aqueous system. In the meantime, a film utilizing Eu-1 as the key component had been successfully fabricated, and exhibited a remarkable potential for the visual recognition of TA and FA. In addition, the luminescence sensing mechanisms of Eu-1 on the above analytes were investigated further in detail.

Manipulating the Morphology and Electronic State of a Two-Dimensional Coordination Polymer as a Hydrogen Evolution Cocatalyst Enhances Photocatalytic Overall Water Splitting

Manipulating the Morphology and Electronic State of a Two-Dimensional Coordination Polymer as a Hydrogen Evolution Cocatalyst Enhances Photocatalytic Overall Water Splitting

Two-dimensional spin-crossover coordination polymers based on the 1,1,2,2-tetra(pyridin-4-yl)ethene ligand.

A series of two-dimensional (2D) spin-crossover coordination polymers (SCO-CPs) [FeII(TPE)(NCX)2]·solv (1: X = BH3, solv = H2O·2CH3OH·DMF; 2: X = Se, solv = H2O·2CH3OH·0.5DMF; 3: X = S, solv = H2O·2CH3OH·0.5DMF) were synthesized by employing 1,1,2,2-tetra(pyridin-4-yl)ethene (TPE) and pseudohalide (NCX-) coligands. Magnetic measurements indicated that complexes 1-3 exhibited SCO behaviors with diminishing thermal hysteresis (7/4/0 K) upon decreasing the ligand-field strength. The critical temperatures (Tc) during spin transition were found to be inversely proportional to the coordination ability parameters (a™) with a linear correlation. The guest effect was also investigated in the solvent-exchanged phases 1-SE/2-SE/3-SE wherein the DMF molecules were replaced by methanol molecules. Compared with 1-3, 1-SE/2-SE/3-SE displayed more abrupt and complete single-step SCO behaviors but narrower thermal hysteretic loops. The results reported here demonstrate that the Tc values of these two families were dominated by the ligand-field strength of the NCX- anions (NCBH3 > NCSe > NCS), whereas the guest effect only modulated the kinetic factor of the SCO nature in this system.

Guest water-induced structural transformation and spin-crossover variation of a two-dimensional Hofmann-type compound.

In this paper, we report a two-dimensional (2D) Hofmann-type spin-crossover coordination polymer [FeII(o-NTrz)2PtII(CN)4]·H2O (o-NTrz = 4-(o-nitrobenzyl)imino-1,2,4-triazole). Due to the remarkable configurational flexibility of triazole-based ligand, the porous structure of this compound can be reversibly regulated by the loss of guest water molecules as a consequence of rotation of o-NTrz. The 180° reorientation of the o-nitrobenzyl moiety not only induces a response of gate-closing/opening of the porous framework but also significantly modulates the spin transition temperature. The present investigation highlights the potential of Hofmann-type SCO compounds with flexible ligands in exploring unusual physical and chemical phenomena.

Synthesis, Structural Characterization and Hirshfeld Surface Analysis of a Novel Cd(II) Coordination Polymer with Mixed N- and O-donor Linker

In the present study, we report the room temperature synthesis of a novel two-dimensional (2D) coordination polymer (CP) having the formula {[Cd(H-PCA)2(H2O)].0.5(H2O).0.5(CH3OH)}n (CP1), where H-PCA represents 4-pyrazolecarboxylate. The synthesis of CP1 was achieved through a one-pot reaction, involving the self-assembly of Cd(OAc)2·2H2O and the multitopic mixed N- and O-donor ligand, 4-pyrazolecarboxylic acid (H2-PCA), in methanol. This method demonstrated high yield and purity, enabling the facile production of multigram quantities of CP1 within a short timeframe. Notably, the synthetic procedure selectively deprotonates the carboxylic acid group while retaining the pyrazole moiety in its protonated form.CP1 has been thoroughly characterized using various analytical techniques, including single-crystal X-ray diffraction, FTIR spectroscopy, elemental analysis, scanning electron microscopy, thermogravimetric analysis, and powder X-ray diffraction. The structural analysis revealed that CP1 features a 3, 5-connected binodal net with the point symbol {4.5.6}{4.55.63.7}, leading to a unique –ths net topology. Through hydrogen bonding connections between adjacent 2D sheets, CP1 further extends into a three-dimensional (3D) supramolecular network due to the presence of coordinated water molecules and the protonated pyrazole group. Additionally, a 3D Hirshfeld Surface analysis accompanied by quantitative 2D fingerprint plots was also investigated to explore the intermolecular interactions.

A two-dimensional semiconducting Cu(i)-MOF for binder and conductive additive-free supercapattery

A two dimensional CuCN-based semiconducting MOF with nitrogen rich ligand has been synthesized which shows supercapattery behaviour. The energy storage device formed by CuCN-MOF exhibits excellent energy density, power density and cyclic stability.

Expanding the dimensionality of bis(tetrazolyl)alkane-based Fe(II) coordination polymers by the application of dinitrile coligands.

Reactions between 1,2-di(tetrazol-2-yl)ethane (ebtz), 1,6-di(tetrazol-2-yl)hexane (hbtz) or 1,1'-di(tetrazol-1-yl)methane (1ditz) and Fe(BF4)2 in the presence of adiponitrile (ADN), glutaronitrile (GLN) or suberonitrile (SUN) resulted in the formation of coordination polymers [Fe(μ-ebtz)2(μ-ADN)](BF4)2 (1), [Fe(μ-hbtz)2(μ-ADN)](BF4)2 (2), [Fe(μ-1ditz)2(GLN)2](BF4)2·GLN (3) and [Fe(μ-1ditz)2(μ-SUN)](BF4)2·SUN (4). It was established that the application of dinitriles allows an increase in the dimensionality of the ebtz and hbtz based systems while maintaining the structure of the polymeric units characteristic of previously studied mononitrile based analogues. In 3 and 4, regardless of the type of dinitrile coligand, the motif of 2D polymeric layers constituted by 1ditz molecules remains preserved. However, the dimensionality of 1ditz based networks is governed by the coordination modes of dinitriles. 3, based on a shorter molecule of glutaronitrile, crystallizes as a two-dimensional (2D) coordination polymer. In this compound, dinitriles coordinate monodentately or play the role of guest molecules. The substitution of glutaronitrile with suberonitrile enables the bridging of neighboring polymeric layers, resulting in a 3D network. The intentional selection of bis(tetrazoles) and dinitriles as building blocks has led, as expected, to obtaining systems with the structure of the first coordination sphere consisting of four tetrazole rings and two axially coordinated nitrile molecules. It created the conditions required for the occurrence of thermally induced spin crossover. Magnetic measurements and single crystal X-ray diffraction studies were used for the characterization of the spin crossover properties of 1-4.

Antibiotic identification in aqueous solution by a two-dimensional cadmium-based coordination polymer with excellent fluorescence properties

Over the past two decades, large amounts of antibiotics have been discharged into the aquatic environment, threatening human health and ecological balance. Meanwhile, numerous reports have documented coordination polymers as a fluorescent sensing material for detecting pollutants in aqueous environments. We successfully synthesized a two-dimensional coordination polymer using Cd2+ ions and the rigid ligand 1-(3,4-dicarboxyphenyl)-4-hydroxypyridin (H2L) and named it [Cd(L)]n (1). In this complex, each cadmium ion exhibits a six-coordinated pattern and forms a two-dimensional network structure with a (6,3)Ia-type topology according to the ToposPro software. In addition, the good stability and excellent fluorescence properties of the complex made it an excellent fluorescent sensor for the identification of ciprofloxacin and oxytetracycline in aqueous solution with low limits of detection (0.28 μM for ciprofloxacin and 36.5 μM for oxytetracycline). Finally, we investigated the detailed mechanism of the fluorescence sensing behavior of the complex by performing density functional theory calculations.

Halogen-Modulated 2D Coordination Polymers for Efficient Hydrogen Peroxide Photosynthesis under Air and Pure Water Conditions.

H2 O2 is a widely used eco-friendly oxidant and a potential energy carrier. Photocatalytic H2 O2 production from water and O2 is an ideal approach with the potential to address the current energy crisis and environmental issues. Three zig-zag two-dimensional coordination polymers (2D CPs), named CuX-dptz, were synthesized by a rapid and facile method at room temperature, showing preeminent H2 O2 photoproduction performance under pure water and open air without any additives. CuBr-dptz exhibits a H2 O2 production rate high up to 1874 μmol g-1  h-1 , exceeding most reported photocatalysts under this condition, even comparable to those supported by sacrificial agents and O2 . The coordination environment of Cu can be modulated by halogen atoms (X=Cl, Br, I), which in turn affects the electron transfer process and finally determines the reaction activity. This is the first time that 2D CPs have been used for photocatalytic H2 O2 production in such challenging conditions, which provides a new pathway for the development of portable in situ H2 O2 photosynthesis devices.

The Synthesis and Crystal Structures of New One- and Two-Dimensional Fe(II) Coordination Polymers Using Imidazole Derivatives

We studied the synthesis and crystal structures of a new two-dimensional (2D) coordination polymer, {FeII(1-Ethyl-imidazole)2[NiII(CN)4]}n (1), and one-dimensional (1D) coordination polymers, {FeII(1-benzyl-imidazole)4[NiII(CN)4]}n (2) and {FeII(1-Allyl-imidazole)4[NiII(CN)4]}n (3). Compound 1 has a 2D sheet structure, which is a traditional Hofmann-like structure. In compound 1, an octahedral FeII ion is coordinated with the nitrogen atoms of the [NiII(CN)4] planar unit at equatorial positions and monodentate imidazole derivatives at axial positions. The layers construct a parallel stacking array. Compounds 2 and 3 have a 1D chain structure. In compounds 2 and 3, the FeIIN6 coordination environment is formed with four imidazole ligands and two [NiII(CN)4]2− metalloligands. In the [NiII(CN)4]2− unit, two CN substituents act as bidentate ligands that form infinite –Ni–C–N–Fe–N–C–Ni– chains. Herein, we discuss the systematic design of polymeric dimensionality.