Nanoporous Coordination Polymers Research Articles

Ab Initio Study of Hydrostable Metal–Organic Frameworks for Postsynthetic Modification and Tuning toward Practical Applications

Metal–organic frameworks (MOFs), a subclass of nanoporous coordination polymers, have emerged as one of the most promising next-generation materials. The postsynthetic modification method, a strategy that provides tunability and control of these materials, plays an important role in enhancing its properties and functionalities. However, knowing adjustments which leads to a desired structure–function a priori remains a challenge. In this comprehensive study, the intermolecular interactions between 21 industrially important gases and a hydrostable STAM-17-OEt MOF were investigated using density functional theory. Substitutions on its 5-ethoxy isophthalate linker included two classes of chemical groups, electron-donating (−NH2, −OH, and −CH3) and electron-withdrawing (−CN, −COOH, and −F), as well as the effect of mono-, di-, and tri-substitutions. This resulted in 651 unique MOF–gas complexes. The adsorption energies at the ground state and room temperature, bond lengths, adsorption geometry, natural bond orbital analysis of the electric structure, HOMO–LUMO interactions, and the predicted zwitterionic properties are presented and discussed. This study provides a viable strategy for the functionalization, which leads to the strongest affinity for each gas, an insight into the role of different chemical groups in adsorbing various gas molecules, and identifies synthetic routes for moderating the gas adsorption capacity and reducing water adsorption. Recommendations for various applications are discussed. A custom Python script to assess and visualize the hypothetical separation of two equal gas mixtures of interest is provided. The methodology presented here provides new opportunities to expand the chemical space and physical properties of STAM-17-OEt and advances the development of other hydrostable MOFs.

Electron transfer bridging by porous seawater fluid

Electron transfer between solid and gas phases in saline is of vital importance to electricity supply, energy storage and conversion, and catalysis. In most cases, seawater does not contribute greatly to the electron transfer process. Here we report a strategy to generate porous fluid by dispersing nanoporous coordination polymer into the seawater. In situ ultraviolet-visible and electrochemical spectroscopy confirms that the porous seawater fluid mediates electron transfer between the solid donor and the dissolved oxygen. The key factors in accelerating electron transfer are found to be (1) the porous electrode, (2) the connection between the porous seawater and the environmental air, and (3) the dynamic condition of the fluid. Enhanced electron transfer between the alloy and the dissolved oxygen leads to an efficient ocean electricity supply strategy based on the porous seawater fluid. • Porous seawater fluid is realized • Efficient solid-gas electron transfer mediated by porous seawater fluid • Potential for a stable electricity supply under the sea based on porous seawater fluid Electron transfer between solid and gas phases in saline is of vital importance for applications in electricity supply, energy storage and conversion, and catalysis. Li et al. realize a strategy to disperse coordination polymers into seawater to obtain a porous fluid, which actively prompts efficient solid-gas electron transfer for power supply under water.

A chemically stable nanoporous coordination polymer with fixed and free Cu2+ ions for boosted C2H2/CO2 separation

Safely and highly selective acetylene (C2H2) capture is a great challenge, because of its highly explosive nature, as well as its nearly similar molecule size and boiling point toward the main impurity of carbon dioxide (CO2). Adsorption separation has shown a promising future. Herein, a new nanoporous coordination polymer (PCP) adsorbent with fixed and free Cu ions (termed NTU-66-Cu) was prepared through post-synthetic approach via cation exchanging from the pristine NTU-66, an anionic framework with new 3, 4, 6-c topology and two kinds of cages. The NTU-66-Cu shows significantly improved C2H2/CO2 selectivity from 6 to 32 (v/v: 1/1) or 4 to 42 (v/v: 1/4) at low pressure under 298 K, along with enhanced C2H2 capacity (from 89.22 to 111.53 cm3·g−1). More importantly, this observation was further validated by density functional theory (DFT) calculations and breakthrough experiments under continuous and dynamic conditions. Further, the excellent chemical stability enables this adsorbent to achieve recycle C2H2/CO2 separation without loss of C2H2 capacity.

An Emerging Family of Hybrid Nanomaterials: Metal–Organic Framework/Aerogel Composites

Metal–organic frameworks (MOFs) are crystalline nanoporous coordination polymers made of metal ions and organic linkers. Aerogels are highly nanoporous amorphous polymers that can be organic, inorganic, or hybrid. Both of these unique materials have been extensively investigated in many laboratories around the world for a wide range of applications ranging from separations to catalysis, resulting in thousands of published articles in a wide variety of journals. MOF/aerogel composites (MOFACs) are a new class of nanostructured materials that are attracting increasing attention because of their favorable properties. The combination of the micro- and mesoporosities of MOFs with the meso- and macroporosities of aerogels makes MOFACs hierarchically multimodal porous materials. With their high surface areas and combined morphological, mechanical, physicochemical, and functional properties of both MOFs and aerogels, MOFACs have demonstrated outstanding performances in various applications. Herein we provide an o...

A nanoporous palladium(II) bridged coordination polymer acting as a peroxidase mimic in a method for visual detection of glucose in tear and saliva.

A nanoporous coordination polymer (NPCP) was prepared from palladium(II) chloride and 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole and is shown to act as a peroxidase mimetic. It can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 which is formed on enzymatic oxidation of glucose by glucose oxidase. Based on these findings, a sensitive glucose test was worked out at 652nm where the intensity if the greenish-blue product is related to the actual concentration of glucose. Figures of merit include (a) rather low Km value (30μM) which evidences the strong binding affinity of the NPCP toward glucose, (b) a high v(max) (8.5M·s-1), (c) a 47nM detection limit, (d) a lifetime of a month, (e) a wide working pH range (2-10), and (f) a 25-80°C temperature range. The assay was applied to non-invasive determination of glucose assay in tear, saliva where the detection limits are found to be 61 and 91nM, respectively. Graphical abstract DSchematic of the mechanism of the peroxidase like catalytic activity of AHMT-Pd NPCPthat was applied in a selective colorimetric method for glucose detection based on TMB oxidation inthe presence of enzymatically generatedH2O2.

Hydrothermal recrystallization of transition metal nitroprussides. Formation of the most stable phases

Hydrothermal recrystallization appears to be an appropriate treatment to explore the structural diversity of porous coordination polymers. In this contribution, such a post-synthesis treatment is applied to divalent transition metal nitroprussides, T[Fe(CN)5NO]∙xH2O with T =Mn, Fe, Co, Ni, Cu, Zn, Cd. This family of compounds forms an interesting series of nanoporous coordination polymers with a wide structural diversity, related to the synthesis route used and the solid hydration degree (x). The effect of a hydrothermal recrystallization of previously prepared fine powders using the precipitation method, on their crystal structure and related properties is herein discussed. In this series of coordination polymers, for Fe, Co, Ni the precipitated powders are obtained as cubic phase, with a high porosity related to presence of systematic vacancies for building unit [Fe(CN)5NO]. For Fe and Co a structural transition, from cubic to orthorhombic, was observed, which is associated to formation of a most compact structure. The crystal structure for the new orthorhombic phases was refined from the collected powder HR-XRD patterns. For Ni, the cubic phase remains stable even for large heating time, which is ascribed to the high polarizing power of this metal. The high porosity for the cubic phase allows an easy accommodation for the local deformations around the Ni atom coordination sphere. The structural information from XRD was complemented with CO2 and H2 adsorption and TG data, IR and UV–vis spectra, and magnetic measurements. The magnetic data, through the presence of spin-orbit coupling for Fe and Co in the two phases, provide fine details on the coordination environment for the metal linked at the N ends of the CN group.

High-throughput powder diffraction measurement system consisting of multiple MYTHEN detectors at beamline BL02B2 of SPring-8.

In this study, we developed a user-friendly automatic powder diffraction measurement system for Debye-Scherrer geometry using a capillary sample at beamline BL02B2 of SPring-8. The measurement system consists of six one-dimensional solid-state (MYTHEN) detectors, a compact auto-sampler, wide-range temperature control systems, and a gas handling system. This system enables to do the automatic measurement of temperature dependence of the diffraction patterns for multiple samples. We introduced two measurement modes in the MYTHEN system and developed new attachments for the sample environment such as a gas handling system. The measurement modes and the attachments can offer in situ and/or time-resolved measurements in an extended temperature range between 25 K and 1473 K and various gas atmospheres and pressures. The results of the commissioning and performance measurements using reference materials (NIST CeO2 674b and Si 640c), V2O3 and Ti2O3, and a nanoporous coordination polymer are presented.

A nanoporous Ag(i) coordination polymer for selective adsorption of carcinogenic dye Acid Red 26

A cationic Ag(i) coordination polymer with 1D nanoporous channels (ca. 1.22 nm diameter) shows the selective and complete removal of carcinogenic dye Acid Red 26 from aqueous solution upon the size-exclusion and charge-matching effect.

Electric-field-induced metastable state of electrical conductivity in polyaniline nanoparticles polymerized in nanopores of a MIL-101 dielectric matrix

Conducting polyaniline PANI has been obtained inside dielectric nanoporous coordination polymer MIL-101. The application of an electric field transforms both bulk PANI and nanocomposite PANI@MIL to a metastable high-conductive state. After a decrease in the applied electric field, PANI and PANI@MIL relax toward a state low-conductive stable by the law ln[σ(t)/σ(τ)] = −(t/τ)n, which is typical of disordered systems with the characteristic time τ of about six hours for PANI and with three times larger time for composite PANI@MIL. The temperature dependences of the electrical conductivity σ(T) of the samples in both high- and low-ohmic states are described by the fluctuation-induced conductivity model. Significant changes in relaxation processes and in the parameters of the fluctuation-induced tunneling conduction in nanocomposite PANI@MIL are due to a decrease in the sizes of polyaniline particles in the MIL-101 matrix to nanometers.

Synthesis of polypyrrole intercalated into channels of nanoporous metal-organic coordination polymer

A procedure has been developed for the intercalation of pyrrole into nanocavities of a metal-organic coordination polymer, chromium terephthalate MIL-101, and oxidative polymerization of pyrrole has been accomplished. The new composite nanomaterial thus obtained, polypyrrole@MIL-101, has been characterized by the data of elemental analysis, X-ray powder diffraction, thermal analysis, and scanning electron microscopy. Its specific surface area has been estimated at 1700 m2/g according to Brunauer-Emmett-Teller.

A new lead(ii) nanoporous three-dimensional coordination polymer: pore size effect on iodine adsorption affinity

A three-dimensional (3D) nanoporous coordination polymer, [Pb(4-bpdb)(μ-NO3)(μ-SCN)]n·1.5CH3OH (TMU-15), was synthesized. In this compound, we successfully loaded the porous crystals with I2 by suspending them in a solution of I2 in cyclohexane.

Highly proton conductive nanoporous coordination polymers with sulfonic acid groups on the pore surface

Three new sulfonated porous coordination polymers (PCPs)/metal-organic frameworks (MOFs) have been synthesized using solvothermal methods. These PCPs possess porous structures with non-coordinating sulfonic acid groups or sulfonate with dimethyl ammonium cations and exhibit high proton conductivity at a low humidity of 60% RH (relative humidity) at ambient temperature.

Size-controlled crystalline basic nanoporous coordination polymers of Zn4O(H2N-TA)3: Catalytically study of IRMOF-3 as a suitable and green catalyst for selective synthesis of tetrahydro-chromenes

Size-controlled crystalline basic nanoporous coordination polymers of IRMOF-3 (Zn4O(H2N-TA)3) and its catalytically study for synthesis of tetrahydro-chromenes was investigated. IRMOF-3 was found to be an efficient, selective and waste-free green solid base for the coupling reaction of dimedone, aldehydes, and malononitrile. The catalyst can be isolated from the reaction mixture and reused at least 5 times.

Hybrid Inorganic–Organic Framework as Efficient Heterogeneous Catalyst for the Synthesis of Allyl Glycidyl Carbonate from CO<SUB>2</SUB> and Allyl Glycidyl Ether

A mixed-linker nanoporous coordination polymer Zn2(HIP)2(bipy)(H2O)2 x H2O (ZnHipBipy) constructed from polyfunctional linker 5-hydroxy isophthalic acid (HIP) and exo-bidentate ligand 4,4'-bipyridyl (bipy) was employed as heterogeneous catalyst for allyl glycidyl carbonate (AGC) synthesis from CO2 and allyl glycidyl ether (AGE) under solventless conditions. Besides being the organic linker, 5-hydroxy isophthalic acid enriches the functionality of the material through accessible hydroxyl group capable of contributing extensive hydrogen bonding interactions. The cycloaddition of CO2 and epoxide was catalyzed through a synergistic pathway offered by inherent hydroxyl group together with the catalytically active metal centre. Method of synthesis and texture of the catalyst were key factors in determining the conversion and selectivity. The effects of reaction parameters like catalyst amount, temperature, CO2 pressure and reaction time on the yield of AGC were also studied.

Synthesis, structure of 3D lanthanide (La(III), Pr(III)) nanoporous coordination polymers containing 1D channels as selective luminescent probes of Pb 2+, Ca 2+ and Cd 2+ ions

Two kinds of 3D coordination polymers, namely, {[La 2(PDA) 3(H 2O) 4]·H 2O} ∞ ( I) and {[Pr 2(PDA) 3(H 2O) 3]·H 2O} ∞ ( 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 N 1O 8 or N 1O 9 polyhedral units connecting to the PDA 2− anions forming tricapped trigonal prism and double-capped cubic antiprism geometries, respectively. Two types of ring motifs as building blocks constructed by La 8C 2O 10 (20-membered ring) and La 4C 2O 6 (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 N 1O 7 or N 2O 7 polyhedral units connecting to the PDA 2− anions forming trigonal dodecahedron and tricapped trigonal prism configurations, respectively. The tetranuclear homometallic motifs formed by Pr 4C 4O 8 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 Pb 2+, Ca 2+ and Cu 2+ or Cd 2+ ions.

Response of Two-Dimensional Polymeric Cadmium Ferrocenyl Disulfonates to Heavy Metal Ions

A sandwich-like 2D infinite framework of {[Cd(pbbm)2(SO3FcSO3)]·(CH3OH)2·(H2O)6} n (1) with nanosized porous structure [Fc(SO3)2Na2 = ferrocene-1,1′-disulphonate, pbbm = 1,1′-(1,3-propylene)-bis-1H-benzimidazole] was prepared by combining d 10 Cd2+ ions with highly conjugated pbbm and disodium ferrocene-1,1′-disulfonate. Experimental results show that 1 could serve as a new fluorescent probe for the detection of many divalent metal ions in water, such as Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Ag+, Cd2+, Hg2+ and Pb2+, and trace organic solvents, including acetone, toluene, methylene chloride, ether, tetrahydrofuran, and methanol. The main product was very different from previous chemosensory materials that only identify one or two metal ions. The powdery multipurpose chemosensory materials proposed here could also sequester dangerous heavy metal ions, especially Pb2+. A computational study of ferrocene-1,1′-disulfonate and 1 gave insight into the process of ion exchange and sorption. This study introduces a promising new field of fluorescent chemosensors based on nanoporous coordination polymers with free functional groups.

Hydrogen adsorption in HKUST-1: a combined inelastic neutron scattering and first-principlesstudy

Hydrogen adsorption in high surface area nanoporous coordination polymers has attracteda great deal of interest in recent years due to the potential applications in energy storage. Herewe present combined inelastic neutron scattering measurements and detailed first-principlescalculations aimed at unraveling the nature of hydrogen adsorption in HKUST-1 (Cu3(1,3,5-benzenetricarboxylate)2), a metal–organic framework (MOF) with unsaturated metal centers. We revealthat, in this system, the major contribution to the overall binding comesfrom the classical Coulomb interaction which is not screened due to theopen metal site; this explains the relatively high binding energies and shortH2–metal distances observed in MOFs with exposed metal sites as compared to traditional ones.Despite the short distances, there is no indication of an elongation of the H–H bond for the boundH2 molecule at the metal site. We find that both the phonon and rotational energy levelsof the hydrogen molecule are closely similar, making the interpretation of theinelastic neutron scattering data difficult. Finally, we show that the orientation ofH2 has a surprisingly large effect on the binding potential, reducing the classical bindingenergy by almost 30%. The implication of these results for the development of MOFmaterials for better hydrogen storage is discussed.

The MEM/Rietveld method with nano-applications – accurate charge-density studies of nano-structured materials by synchrotron-radiation powder diffraction

Structural studies of materials with nano-sized spaces, called nano-structured materials, have been carried out by high-resolution powder diffraction. Our developed analytical method, which is the combination of the maximum-entropy method (MEM) and Rietveld refinement, the so-called MEM/Rietveld method, has been successfully applied to the analysis of synchrotron-radiation (SR) powder diffraction data measured at SPring-8, a third-generation SR light source. In this article, structural studies of nano-porous coordination polymers and endohedral metallofullerenes are presented with the advanced technique of SR powder experiment. The structure of the adsorbed guest molecule in the coordination polymer and encapsulated atoms in the fullerene cage are clearly revealed by the MEM charge density. The methodology of MEM/Rietveld analysis is also presented.

Structural and Magnetic Properties of Layered Copper(II) Coordination Polymers Intercalating s and f Metal Ions

The nanoporous coordination polymer [Cu(pyrimidin-2-olate-N1,N3)2]n (1C) of the sodalite zeotype sorbs a variety of metal nitrates [M(NO3)m, M = Na+, K+, Rb+, Tl+, Ca2+, Sr2+, Ba2+, Pb2+, La3+, Nd3+, Gd3+, Er3+] from H2O/MeOH solutions, with a concomitant structural change to a layered [Cu(pyrimidin-2-olate-N1,N3)2]n.[M(NO3)m]n/2 (MNO3@1L) coordination framework. Single-crystal X-ray diffraction analyses revealed that the layers are based on Cu4(pyrimidin-2-olate-N1,N3)4 square grids of copper(II) ions bridged by N1,N3 exobidentate ligands, displaying a structural motif of the metallacalix[4]arene type in pinched cone conformation. The interlayer space is occupied by the guest metal nitrates, each metal being coordinated by (at least) the four oxygen atoms of a metallacalix[4]arene. Magnetic measurements on the MNO3@1L series denoted a weak ferromagnetic ordering taking place below the Néel temperatures (typically close to 35 K), arising from spin-canting phenomena of the antiferromagnetically coupled copper centers. When M = Nd3+, Gd3+, or Er3+, additional magnetic ordering is observed at lower temperatures, which, on the basis of static and dynamic magnetic susceptibility measurements, can be attributed to copper- lanthanide interactions.

Temperature- or Guest-Induced Drastic Single-Crystal-to-Single-Crystal Transformations of a Nanoporous Coordination Polymer

Aside from a temperature-induced structural transformation, a new nanoporous coordination polymer [Ag6Cl(atz)4].OH.6H2O (Hatz = 3-amino-1,2,4,-triazole) comprised of interpenetrated Ag3(atz)2 coordination nets exhibits a single-crystal-to-single-crystal transformation of a 5-fold to 6-fold net interpenetration change triggered by guest desorption/absorption.