Open-framework Materials Research Articles

Template-Designed Syntheses of Open-Framework Zinc Phosphites with Extra-Large 24-Ring Channels

The rational selection of the templating agents or structure-directing agents (SDAs) is important for the designed synthesis of open-framework materials with specific channel structures. By utilizing organic amines that are predicted by computer simulations as the templates or SDAs, such as cyclohexylamine (CHA), cyclopentylamine (CPA), and n-propylamine, three new open-framework zinc phosphites, including (C6H14N)2[Zn3(HPO3)4] (ZnHPO-CJ2), (C5H12N)2[Zn3(HPO3)4] (ZnHPO-CJ3), and (C3H10N)2[Zn3(HPO3)4] (ZnHPO-CJ4), have been hydrothermally prepared with desired extra-large 24-ring channels analogous to (C4NH12)2[Zn3(HPO3)4] (ZnHPO-CJ1). Their structures are characterized by single-crystal and powder X-ray diffraction, inductively coupled plasma (ICP), IR, and thermogravimetric analyses. These organic amines predicted based on nonbonding interactions of host–guest show good matching in the space and charge density with the host inorganic framework. As with ZnHPO-CJ1 and other known extra-large micropore materials with high framework charge density, the 24-rings of these compounds are assembled around multiple small amines, exemplifying the cooperative templating mechanism of multiple small organic cations in the formation of extra-large micropore open-framework materials. This work demonstrates a useful strategy toward the template-designed synthesis of microporous materials with extra-large micropores.

Wavelength‐Dependent Photochromic Inorganic–Organic Hybrid Based on a 3D Iodoplumbate Open‐Framework Material

Plumb pudding: A 3D iodoplumbate inorganic–organic hybrid built from purely octahedral units, obtained through in situ solvothermal synthesis, belongs to a new structural subclass of organically templated inorganic open-framework materials. It exhibits the properties of its 1D incomplete-cubane-chain building block and shows ordered and periodic quantum-wire behavior, as well as a wavelength-dependent photochromic response.

Inorganic clathrate-II materials of group 14: synthetic routes and physical properties

Crystalline open-framework and nanoporous materials have long attracted the attention of chemists, physicists, and materials scientists. The intriguing structures such materials exhibit are often intimately related to the unique physical properties they possess. This article reviews recent developments in the preparation and characterization of one such class of inorganic materials, those comprised of group 14 elements crystallizing with the clathrate-II crystal structure. These materials correspond to expanded forms and, in some cases, metastable allotropes of Si, Ge, and Sn. Just as interesting as the structure and properties that group 14 clathrate-II materials display is the diverse range of synthetic techniques used to prepare them and these techniques are discussed. We review the work to date characterizing the physical properties of group 14 clathrate-II materials with emphasis placed on structure–property relationships, in particular with regard to the electronic and transport properties.

Manganese and Magnesium Homochiral Materials: Decoration of Honeycomb Channels with Homochiral Chains

Five homochiral open-framework materials based on manganese and magnesium camphorates exhibit homochiral connectivity from one- to three-dimensions, highlighting the versatility of the synthetic system reported here. Two compounds contain a column of homochiral chains lining up the honeycomb channels of 3-D metal−oxygen frameworks, an unusual feature previously unobserved in inorganic−organic hybrids.

Highly Selective Ferric Ion Sorption and Exchange by Crystalline Metal Phosphonates Constructed from Tetraphosphonic Acids

With the motivation of searching for highly selective ferric ion sorbents, two open-framework and microporous materials, {[Pb7(HEDTP)2(H2O)] x 7H2O}n (1) and {[Zn2(H4EDTP)] x 2H2O}n (2) [H8EDTP = N,N,N',N'-ethylenediaminetetrakis(methylenephosphonic acid)], have been synthesized and structurally characterized. The structure of compound 1 results from the seven crystallographically different lead atoms that are bridged by two HEDTP(7-) ligands to yield a three-dimensional microporous framework with tunnels along the a and b axes. Compound 2 features a layer architecture built of square waves along the a axis. The layers are connected by hydrogen bonds between uncoordinated phosphonate oxygen atoms to form a three-dimensional supramolecular network, with one-dimensional tunnels along the a axis. Both compounds 1 and 2 exhibited high ion sorption and exchange capacities for millimolar concentrations of Fe(III). Specifically, when 0.01 g of 1 (or 2) was added to 5 mL of a 1 mM metallic chloride aqueous solution and the mixture was allowed to stand for 2 days at room temperature, compound 1 adsorbed nearly 100% of Fe(III) and compound 2 adsorbed 96.8% of Fe(III). They were also found to adsorb ferric ions selectively over other metal ions, such as Ca(II), Cr(II), Mn(II), Cu(II), Zn(II), Cd(II), etc. Their special ferric ion uptake capacities may be attributed to the cation exchange, coordination bonding, and electrostatic attraction between ferric ions and metal phosphonates.

Old Materials with New Tricks: Multifunctional Open‐Framework Materials

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Structural chemistry and zeolitic properties of mixed oxalates with two open-framework types based on eight coordinate metals

Abstract Two families of open-framework materials have been obtained from the assembly of MO 8 polyhedra and oxalate groups as building blocks. The compounds can be formulated as [MM′(C 2 O 4 ) 4 ] 2− (M″ y ) 2+ · (4 + x )H 2 O ( y is 2 for monovalent M″ metals and 1 for divalent M″ metals), in which the sum of the valences of the two metals M and M′ involved in the anionic framework is six. The water molecules and counter cations, located in the voids of the structure, lead to zeolitic or cation dynamic properties.

Amine-Controlled Assembly of Metal−Sulfite Architecture from 1D Chains to 3D Framework

Whereas open-framework materials have been made in a variety of chemical compositions, few are known in which 3-connected SO3(2)- anions serve as basic building units. Here, we report four new metal-sulfite polymeric structures, (ZnSO3)Py (1, py = pyridine), (ZnSO3)2(2,2'-bipy)H2O (2, 2,2'-bipy = 2,2'-bipyridine), (ZnSO3)2(TMDPy) (3, TMDPy = 4,4'-trimethylenedipyridine), and (MnSO3)2en (4, en = ethylenediamine) that have been synthesized hydrothermally and structurally characterized. In these compounds, low-dimensional 1D and 2D inorganic subunits are assembled into higher 2D or 3D covalent frameworks by organic ligands. In addition to the structure-directing effect of organic ligands, the flexible coordination chemistry of Zn2+ and SO3(2)- also contributes to the observed structural diversity. In compounds 1-3, Zn2+ sites alternate with trigonal pyramidal SO3(2)- anions to form three types of [ZnSO3]n chains, whereas in compound 4, a 2D-corrugated [MnSO3]n layer is present. Compound 1 features a rail-like chain with pendant pyridine rings. The pi-pi interaction between 2,2'-bipy ligands is found between adjacent chains in compound 2, resulting in 2D sheets that are further stacked through interlayer hydrogen bonds. Compound 3 exhibits a very interesting inorganic [(ZnSO3)2]n chain constructed from two chairlike subunits, and such chains are bridged by TMDPy ligands into a 2D sheet. In compound 4, side-by-side helical chains permeate through 2D-corrugated [MnSO3]n layers, which are pillared by neutral ethylenediamine molecules into a 3D framework that can be topologically represented as a (3,6)-connected net. The results presented here illustrate the rich structural chemistry of metal-sulfites and the potential of sulfite anions as a unique structural building block for the construction of novel open-framework materials, in particular, those containing polymeric inorganic subunits that may have interesting physical properties such as low-dimensional magnetism or electronic properties.

Na[H2TETA]0.5 [ZnPO4]2×0.5H2O or TJPU‐1: A New Zincophosphate Open‐Structure Co‐Templated by Sodium and Organoamine.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

A flexible interpenetrating coordination framework with a bimodal porous functionality

Introducing a functional part into open-framework materials that tunes the pore size/shape and overall porous activity will open new routes in framework engineering and in the fabrication of new materials. We have designed and synthesized a bimodal microporous twofold interpenetrating network {[Ni(bpe)2(N(CN)2)](N(CN)2)(5H2O)}n (1), with two types of channel for anionic N(CN)2- (dicyanamide) and neutral water molecules, respectively. The dehydrated framework provides a dual function of specific anion exchange of free N(CN)2- for the smaller N3- anions and selective gas sorption. The N3-exchanged framework leads to a dislocation of the mutual positions of the two interpenetrating frameworks, resulting in an increase in the effective pore size in one of the counterparts of the channels and a higher accommodation of adsorbate than in the as-synthesized framework (1), showing the first case of controlled sorption properties in flexible porous frameworks.

Computational simulation study towards the synthesis of extra-large microporous materials

The rational synthesis of open-framework materials with extra-large micropores is a challenging topic in the field of zeolites science. Employing computational methods, the charge-density matching, space matching, and non-bonding interactions of the host framework and guest template molecules have been studied for some known microporous materials with 14-, 16-, 18-, 20- and 24-ring extra-large micropores. The host–guest relationship in different synthetic systems has been summarized. This study provides a useful guidance for rational choice of templates for the synthesis of extra-large microporous materials with predetermined structures and compositions.

Na[H2TETA]0.5[ZnPO4]2·0.5H2O or TJPU-1: A New Zincophosphate Open-structure Co-templated by Sodium and Organoamine

Synthetic open-structured materials attract increasing attention for wide applications in catalysis, ion-exchange or intercalation. Metal phosphates are possibly the fastest expanding group of open-framework inorganic materials in the past decade. The structural diversity that stemmed from the variable coordination number and oxidation states has directed to the extensive expansion of open-framework metal phosphates. Since the bivalent metal phosphates (+2, +5) are associated with the same total charge as aluminosilicate zeolites (+3, +4), phosphate-based framework structures containing bivalent metals are considerably pursued. After the discovery of the first open-framework zincophosphate with zeolite topologies reported by G. D. Stucky, a great deal of effort has been devoted to isolating novel open-structures within this system. And this compound group has experienced extraordinary expansion in terms of the diversity of their structures and compositions. Zincophosphates with zero-, one-, two-, and three-dimensional architectures have been isolated, in which an eye-catching result is the gigantic pore structure with 24-membered rings in ND-1. This variety was achieved by varying a number of factors that can influence the structure, including template, pH, solvent, reaction temperature, additives, zinc source and others. On the other hand, the pursuit of chiral molecular sieves is of great interest with respect to the applications in enantioselective separation and syntheses. However, only a few inorganic chiral frameworks were known up to now. For the syntheses of open-structured crystals, both alkali cations and organoamine are used as structure directing reagent separately in the literatures. Although there are some compound containing both of them, systematically investigation of the co-template effect of alkali cations and organoamines is seldom. Our group has focused on metal phosphate open-structures for many years. Recently, we are interest in exploring new open-framework metal phosphates co-templated by alkali cation and organoamine. This approach has successfully yielded a new zincophosphate openstructure, Na[H2TETA]0.5[ZnPO4]2·0.5H2O (TETA = triethylenetetraamine) or TJPU-1 (TJPU = Tianjin Polytechnic University), with the zeolite CZP topology. This compound contains left-handed chiral channels along its c axis. Here we report its synthesis and crystal structure. Experimental Section

Old materials with new tricks: multifunctional open-framework materials

The literature on open-framework materials has shown numerous examples of porous solids with additional structural, chemical, or physical properties. These materials show promise for applications ranging from sensing, catalysis and separation to multifunctional materials. This critical review provides an up-to-date survey to this new generation of multifunctional open-framework solids. For this, a detailed revision of the different examples so far reported will be presented, classified into five different sections: magnetic, chiral, conducting, optical, and labile open-frameworks for sensing applications. (413 references.)

Dipole Moment, Hydrogen Bonding and IR Spectrum of Confined Water

Drastic changes can take place in the structure, dynamics, and thermodynamics of a fluid when it is confined to spaces of molecular dimensions, as compared to its bulk counterpart. Water confinement in the nanometer-scale channels and pores of inorganic open framework materials, such as zeolites, are of great scientific interest. Zeolites are crystalline aluminosilicates, with various controlled pore sizes and connectivities. [1] From a practical point of view, water plays a key role in many applications, includingion-exchang e and separation. From a more general point of view the interaction of water with solid surfaces is of key importance for many chemical and physical processes. However, our present understandingof interfacial or confined water at the molecular level is still very limited. Most of the experimental techniques are difficult to carry out in nanometer environments. Theoretical investigation is, thus, a great help for a better understanding of confined water properties. Classical simulations have recently been performed aimed at understandingthe structure, dynamics, and thermodynamics of water confined in carbon micropores or nanotubes [2, 3] and zeolites. [4–8] However, the quantum nature of bondingin water can only be captured by ab initio calculations. Elaborate treatments of the electronic density are usually limited to small clusters (or a few adsorbed molecules) and restricted to equilibrium structures. The Car–Parrinello molecular dynamics method (CPMD) [9] offers an alternative route to capture the electronic properties of molecules, as well as dynamical effects. Such DFT-based ab initio molecular dynamics calculations have been already applied to bulk water, [10] interfacial water on Si surfaces, [11] and zeolitic materials. [12, 13] Most of the CPMD stud

Adhered Zeolite Preparation on and Within a Muscovite Mica by Hydrothermal Growth

AbstractZeolites and other open framework materials provide a powerful tool for remediation and solidification of a range of cationic wastes (e.g.NH4+${\rm{NH}}_4^ + $, Pb2+) due to the combined properties of large surface area and cation exchange capacity. However, practical barriers exist to the continued expansion of their use, including handling issues related to the fine particle size, and continued ion exchange following waste adsorption. This study examines the synthesis and characterization of zeolites adhered to a muscovite mica wafer, in order to assess if practical benefit can be derived from the preparation of layered composite materials. The paper demonstrates that increased metal adsorption, as demonstrated by surface chemical composition, can be induced in regions by growth of zeolite on and within the lamellar structure of the matrix. X-ray diffraction studies suggest that a site-specific crystallization mechanism controls the zeolite type and extent of growth, thereby reducing control over the zeolites prepared. However, although increased adsorption has been introduced to the mica, the amount of zeolite added is small (<50 mg per gram of muscovite), and thus any adsorption is very limited.

The use of hydrothermal methods in the synthesis of novel open-framework materials

The preparation of inorganic compounds, exhibiting open-framework structures, by hydrothermal methods has been presented. To illustrate the efficacy of this approach, few select examples encompassing a wide variety and diversity in the structures have been provided. In all the cases, good quality single crystals were obtained, which were used for the elucidation of the structure. In the first example, simple inorganic network compounds based on phosphite and arsenate are described. In the second example, inorganic-organic hybrid compounds involving phosphite/arsenate along with oxalate units are presented. In the third example, new coordination polymers with interesting structures are given. The examples presented are representative of the type and variety of compounds one can prepare by careful choice of the reaction conditions.

Catalytic deNO x properties of novel vanadium oxide based open-framework materials

The deNO x catalytic properties of a new class of open-framework structure materials, Li6[Mn3(H2O)12V18O42(XO4)] · 24H2O (X = V, S) (1), [Fe3(H2O)12 V18O42(XO4)] · 24H2O (X = V, S) (2), [Co3(H2O)12V18O42(XO4)] · 24H2O (X = V, S) (3), and Li6[Ni 3 II (H2O)12V 16 VI V 2 V O42(SO4)] · 24H2O (4), have been studied. The crystal structures of these novel systems consist of three-dimensional arrays of vanadium oxide clusters {V18O42(XO4)} , as building block units, interlinked by {–O–M–O–} (M = Mn, 1; M = Fe, 2; M = Co, 3; M = Ni, 4) bridges. Their open-framework structures contain cavities, similar to those observed in conventional zeolites, which are occupied by exchangeable cations and/or readily removable water of hydration. The catalysts derived from these materials were tested for the selective catalytic reduction (SCR) of nitrogen oxides {NO x } into N2 using a hydrocarbon, propylene, as the reducing agent. The catalysts were ineffective under lean burn conditions. However, the new catalysts, especially the one derived from the cobalt derivative (3), showed intriguing deNO x activity under rich conditions. They remove up to ~ 99% of the toxic NO x emissions in 1.5% O2 with 100% selectivity to N2. The active phase of the catalysts exhibit good stability, can be readily regenerated, and are selective to the desired product-N2. The catalytic reactions occur at moderately low temperatures (400–500 °C). The catalysts were characterized by FT-IR, temperature programmed reactions (TPR and TPO), SEM, BET surface area measurements, elemental analysis, and X-ray diffraction (XRD). Additional advanced techniques were used to further characterize the catalyst phases that showed most promising deNO x activity and increased tolerance to oxygen.

The Synthesis and Characterization of a New Layered Chlorozincophosphate Zn(HPO4)Cl[C4H10N

Along a systematic study of open-framework materials aiming at producing new molecular sieves, we characterized a new zincophosphate Zn(HPO4)Cl[C4H10N]. It was synthesized under mild conditions (r.t.) in the presence of pyrrolidinium as an organic-structure directing agent. The structure of this compound, determinated by single crystal X-ray diffraction, consists of anionic parallel [Zn(HPO4)Cl]− sheets alternating with thick slabs of organic molecules (C4H10N)+. These latters are linked to the anionic sheets through hydrogen bonds. Zn(HPO4)Cl[C4H10N] crystallizes in the monoclinic system and the space group C2/c (No. 9) with cell parameters a = 24,83(9), b = 9,258(5), c = 8.778(3), β = 110,45(4), Z = 8, V = 1891.0(14) Åt3, R = 0.045, and Rw = 0.07. Solid state 31P and 13C MAS NMR spectroscopies are in agreement with the X-ray structure.

Evolution of the Structural Chemistry of Vanadium Organodiphosphonate Networks and Frameworks: Structural Consequences of Fluoride Incorporation in the Development of Stable Phases with Void Channels

Hydrothermal reactions of solutions containing a vanadate source, an organodiphosphonate, an organonitrogen component, and HF (V/P/O/F) yield a series of oxyfluorovanadium-diphosphonates with charge-compensation provided by organoammonium cations or hydronium cations. While V/P/O/F networks provide the recurrent structural motif, the linkage between the layers and the details of the polyhedral connectivities within the layers are quite distinct for the five structures of this study. [H2pip][V4F4O2(H2O)2{O3P(CH2)3PO3}2] (1) (pip = piperazine) is a conventional three-dimensional (3D) "pillared" layer structure, whose V/P/O/F networks are buttressed by the propylene chains of the diphosphonate ligands. In contrast, [H2en][V2O2F2(H2O)2{O3P(CH2)4PO3}] (2) and [H2en]2[V6F12(H2O)2{O3P(CH2)5PO3}2 {HO3P(CH2)5PO3H}] (3) are two-dimensional (2D) slablike structures constructed of pairs of V/P/O/F networks sandwiching the pillaring organic tethers of the diphosphonate ligands. Despite the common overall topology, the layer substructures are quite different: isolated {VO5F} octahedra in 2 and chains of corner-sharing {VO(3)F(3)} octahedra in 3. The 3D structure of [H2en]2[V7O6F4(H2O)2{O3P(CH2)2PO3}4].7H2O (4.7H2O) exhibits a layer substructure that contains the ethylene bridges of the diphosphonate ligands and are linked through corner-sharing octahedral {VO6} sites. The connectivity requirements provide large channels that enclose readily removed water of crystallization. The structure of [H3O][V3F2(H2O)2{O3P(CH2)2PO3}2].3.5H2O (5.3.5H2O) is also 3D. Because of the similiarity with 4.7H2O, it exhibits V/P/O/F layers that include the organic tethers of the diphosphonates and are linked through corner-sharing {VO6} octahedra. In contrast to the network substructure of 4.7H2O, which contains binuclear and trinuclear vanadium clusters, the layers of 5.3.5 H2O are constructed from chains of corner-sharing {VO4F2} octahedra. Thermal studies of the open framework materials 4 and 5 reveal that incorporation of fluoride into the inorganic substructures provides robust scaffoldings that retain their crystallinity to 450 degrees C and above. In the case of 4, dehydration does not change the powder X-ray diffraction pattern of the material, which remains substantially unchanged to 450 degrees C. In the case of 5, there are two dehydration steps, that is, the higher temperature process associated with loss of coordinated water. This second dehydration results in structural changes as monitored by powder X-ray diffraction, but this new phase is retained to ca. 450 degrees C. The materials of this study exhibit a range of reduced oxidation states: 1 is mixed valence V(IV)/V(III) while 2 and 4.7H(2)O are exclusively V(IV) and 3 and 5.3.5H2O are exclusively V(III). These oxidation states are reflected in the magnetic properties of the materials. The paramagnetism of 1 arises from the presence of V(III) and V(IV) sites and conforms to the Curie-Weiss law with C = 2.38 em K/(Oe mol) and = -66 K with mu(eff) (300 K) = 4.33 mu(B). Compounds 3-5 exhibit Curie-Weiss law dependence of magnetism on temperature with mu(eff) (300 K) = 5.45 mu(B) for 3 (six V(III) sites), mu(eff) = 4.60 mu(B) for 4 (seven V(IV) sites) and mu(eff) = 4.13 mu(B) for 5 (two V(III) sites). Compound 2 exhibits antiferromagnetic interactions, and the magnetism may be described in terms of the Heisenberg linear antiferromagnetic chain model for V(IV). The effective magnetic moment at 300 K is 2.77 mu(B) (two V(IV) sites).

Organically‐Templated Metal Sulfates, Selenites and Selenates

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.