Zeotype Structures Research Articles

Influence of carbon casting loading and ultrasound irradiation on catalytic design of Al–Si–P zeotype nanostructure for biofuel production

Due to the large size of free fatty acid molecules, they cannot diffuse into Al–Si–P Zeotype pores in the biofuel production process. Therefore, in the current work, to rectify this problem, in the synthesis of Al–Si–P zeotype by hydrothermal method, various weight percentages of the carbon casting and ultrasound waves for the uniform of the materials were used. Moreover, to enhancement the acidic strength and catalyst performance, Ceric oxide was accommodated on the Al–Si–P zeotype structure by sono-solvothermal synthesis. TPD-NH3, FESEM, HRTEM, BET-BJH, and EDX analyses were utilized for characterizing the samples developed in the present work. BET analysis has revealed that the optimized percentage of charcoal active is 4 wt %. By adding the sonication technique at the stage accommodating Ceric oxide on Al–Si–P zeotype, the conversion percentage increased from 77 to 94%. Test of the capability of modified Al–Si–P Zeotype with sonication and carbon casting to produce biofuel from waste oil delivered a conversion of 91.5%. Kinetic studies have shown that reaction of oil to biofuel is of the first degree, and the modified Al–Si–P Zeotype with sonication and carbon casting has the highest rate constant (0.0014 min−1) among all of the synthesized samples.

Cage-Defining Ring: A Molecular Sieve Structural Indicator for Light Olefin Product Distribution from the Methanol-to-Olefins Reaction

The methanol-to-olefins (MTO) process produces high-value-added light olefins from nonpetroleum sources. Acidic zeotypes containing cages bounded by 8-ring (small-pore) windows can effectively catalyze the MTO reaction, since their cages can accommodate the necessary aromatic intermediates that produce the light olefin products that escape. While progress on the mechanisms of the MTO reaction continues, zeotype structure–reaction property relationships have yet to be elucidated. Here, we report MTO reaction results from various small-pore, cage-containing silicoaluminophosphate/metalloaluminophosphates (SAPO/MAPOs) and zeolites under the same reaction conditions. The MTO behaviors of microporous materials having the following topologies are investigated: LEV, ERI, CHA, AFX, SFW, AEI, DDR, RTH, ITE, SAV, LTA, RHO, KFI, and UFI. The previous observation that light olefin product distributions from a series of small-pore, cage-containing zeolites can be classified into four structural categories is further supported by the results shown here from zeolite structures not investigated in the previous study and SAPO and MAPO materials with isostructural frameworks to all the zeolites. Additionally, these data reveal that light olefin product distributions are very similar over a given topology independent of framework composition. To develop a structure–property relationship between the framework topology and the MTO light olefin product distribution, the concept of the cage-defining ring size is introduced. The cage-defining ring size is defined as the minimum number of tetrahedral atoms of the ring encircling the center of the framework cages in the molecular sieve topology. It is shown that the cage-defining ring size correlates with MTO light olefin product distribution.

STA-20: An ABC-6 Zeotype Structure Prepared by Co-Templating and Solved via a Hypothetical Structure Database and STEM-ADF Imaging

A microporous silicoaluminophosphate with a novel topology type, STA-20, has been prepared via a dual templating method using hexamethylene bisdiazabicyclooctane (diDABCO-C6) and trimethylamine as cotemplates. Its structure has been solved and confirmed using a multitechnique approach that included the use of a hypothetical zeolite database to obtain a candidate starting structure, followed by scanning transmission electron microscopy with annular dark field imaging and Rietveld refinement. STA-20 is a member of the ABC-6 family of zeotype structures. The structure has trigonal symmetry, P-31c, with a = 13.15497(18) A and c = 30.5833(4) A in the calcined form. It has a 12-layer stacking sequence of 6-rings (6Rs), AABAABAACAAC(A), which contains single and double 6R units. In addition to d6r, can, and gme cages, STA-20 possesses the longest cage observed in an ordered ABC-6 material, giving a 3D-connected pore system limited by 8R windows. Models for the location of the templates within cages of the framew...

ChemInform Abstract: Hollow Zeolite Structures: An Overview of Synthesis Methods

AbstractReview: 105 refs.

Hollow Zeolite Structures: An Overview of Synthesis Methods

Hollow capsules with dimensions below 1 μm have recently attracted much attention due to their potential applications as catalysts as well as biomedical and pharmaceutical vectors for controlled drug delivery. Among them, hollow zeolites are particularly interesting because they possess (i) a crystalline structure, which greatly improves their hydrothermal and chemical stability as compared to amorphous silica analogs and (ii) a microporous network that acts as a shape-selective membrane. Moreover, their properties can be continuously tuned by changing their composition, in particular the framework aluminum content. In this perspective review, we examine the recent progress in the development of synthetic methods for the preparation of hollow zeolite and zeotype structures, from templating routes providing large polycrystalline capsules to controlled dissolution methods leading to nanometer-sized hollow single crystals. The applications of these materials will be illustrated and discussed, namely their ma...

Prediction of the formation of microporous aluminophosphates containing (6, 8)-rings using support vector machines

A support vector machine (SVM) method has been used on the database of aluminophosphate (AlPO) synthesis with ca. 1700 reaction data to predict the formation of AlPOs with (6, 8)-rings based on 20 synthetic parameters associated with the gel composition, solvent and templates. Furthermore, four zeotype structures with different channel systems, such as AEN, AWO, ERI and CHA have been computational classified in the family of (6, 8)-ring-containing AlPOs. Analysis results reveal that several synthetic parameters, particular the molar ratio of solvent/Al2O3 (F3), and the Van der Waals (VDW) volume (F14), the greatest length (F11), and the number of free rotated single bond (F20) of templates have significant effects in directing the formation of target structure. Using single or combinations of several parameters, a better classifier can be trained to distinguish the (6, 8)-ring-containing AlPOs with desired zeotype structure or not, and the classification accuracy is about 85%. This work demonstrates that the computational method together with database of AlPO synthesis provides a possibility to establish the relationship between the synthetic factors and the resulting structures, which is important in guiding the rational synthesis of microporous aluminophosphate materials.

Luminescent carbon dots in a new magnesium aluminophosphate zeolite

A new magnesium aluminophosphate JU92-300 with novel zeotype structure and 8-ring channels has been prepared by calcination of microporous JU-92 under 300 °C. Well dispersed C-dots are prepared by using JU92-300 as a support host. Such C-dots@zeolite materials exhibit excitation-dependent photoluminescent behavior, as well as tunable fluorescence with high quantum yields.

Luminescent MTN-Type Cluster–Organic Framework with 2.6 nm Cages

From a basic tetrahedral Cu(4)I(4) cluster, a new MTN-type cluster-organic framework (COZ-1) containing giant 6(4)5(12) and 5(12) cages was successfully constructed. The 6(4)5(12) cage has an inner diameter of 2.6 nm and a large pore volume of 9.2 nm(3); these tetrahedral Cu(4)I(4) clusters with bulky size offer new opportunities for not only the formation of 4-connected zeotype structures but also the integration of porosity and photoluminescent properties from both the cluster and the framework.

ChemInform Abstract: Progress in Heteroatom‐Containing Aluminophosphate Molecular Sieves

AbstractReview: 35 refs.

Green-Chemical Synthesis of ETS-4 Zeotypes for Photocatalytic Hydrogen Production

Pristine ETS-4, a microporous titanosilicate zeotype material was successfully synthesized by using inorganic alkaline-sols as precursors for the first time. Use of halogen/organic free medium, drastic reduction in excess amount of alkali precursors and short synthesis time makes this methodology much more versatile. Sr-ETS-4 material was prepared using ion-exchange process. Structural, optical, bulk and surface properties of the synthesized materials were thoroughly examined and their properties are interpreted. The photocatalytic experiments were conducted under UV light irradiation. Further, Sr-ETS-4 material has showed ca. 4 times higher photocatalytic efficiency for photocatalytic methanol reforming as compared with pristine ETS-4 catalyst. The observed higher photocatalytic efficiency of Sr-ETS-4 catalyst might be attributed to better electron transfer properties of Sr-ion and semiconducting property of one-dimensional titanium chains within zeotype structure.

Progress in heteroatom-containing aluminophosphate molecular sieves

Over the past 30 years, heteroatom-containing aluminophosphate molecular sieves as a prime class of heterogeneous single-site solid catalysts have been quickly developed since the first discovery of aluminophosphate molecular sieves in 1982, and a large variety of such materials with 48 unique zeotype structures have been prepared. This work mainly presents the progress in the development of heteroatom-containing aluminophosphate molecular sieves with new zeolite structures and variable framework compositions in recent years.

Lightweight nanoporous metal hydroxide-rich zeotypes

Nanoporous materials have important industrial applications as molecular sieves, catalysts and in gas separation and storage. They are normally produced as moderately dense silicates (SiO(2)) and aluminosilicates making their specific capacities for the uptake and storage of gases, such as hydrogen, relatively low. Here we report the synthesis and characterization of lightweight, nanoporous structures formed from the metal hydroxide Be(OH)(2) in combination with relatively low levels of framework phosphate or arsenate. Three new zeotype structures are described, constructed mainly of Be(OH)(4) tetrahedra bridged through hydroxide into three-membered rings; these units link together to produce several previously unknown zeotype cage types and some of the most structurally complex, nanoporous materials ever discovered. These materials have very low densities between 1.12 and 1.37 g cm(-3) and theoretical porosities of 63-68% of their total volume thereby yielding very high total specific pore volumes of up to 0.60 cm(3) g(-1).

Zeolitic Polyoxometalate-Based Metal−Organic Frameworks (Z-POMOFs): Computational Evaluation of Hypothetical Polymorphs and the Successful Targeted Synthesis of the Redox-Active Z-POMOF1

The targeted design and simulation of a new family of zeolitic metal-organic frameworks (MOFs) based on benzenedicarboxylate (BDC) as the ligand and epsilon-type Keggin polyoxometalates (POMs) as building units, named here Z-POMOFs, have been performed. A key feature is the use of the analogy between the connectivity of silicon in dense minerals and zeolites with that of the epsilon-type Keggin POMs capped with Zn(II) ions. Handling the epsilon-Keggin as a building block, a selection of 21 zeotype structures, together with a series of dense minerals were constructed and their relative stabilities computed. Among these Z-POMOFs, the cristobalite-like structure was predicted to be the most stable structure. This prediction has been experimentally validated by the targeted synthesis of the first experimental Z-POMOF structure, which was strikingly found to possess the cristobalite topology, with three interpenetrated networks. Crystals of [NBu(4)](3)[PMo(V)(8)Mo(VI)(4)O(36)(OH)(4)Zn(4)(BDC)(2)].2H(2)O (Z-POMOF1) have been isolated under hydrothermal conditions from the reduction of ammonium heptamolybdate in the presence of phosphorous acid and Zn(II) ions. Tetrabutylammonium cations play the role of counterions and space-filling agents in this tridimensional interpenetrated framework. Moreover, the electrochemistry of the epsilon-Keggin POM is maintained and can be exploited in the insoluble Z-POMOF1 framework, as demonstrated by the electrocatalytic reduction of bromate.

Inorganic alkaline-sols as precursors for rapid synthesis of ETS-10 microporous titanosilicates and their photocatalytic reforming of methanol under visible-light irradiation

Pristine ETS-10 and anion-modified ETS-10 microporous titanosilicate catalysts were successfully synthesised by using inorganic alkaline-sols as precursors for the first time. Furthermore, use of halogen/organic-free medium and short time synthesis (within 5 h) makes this methodology even more versatile and efficient. We have noticed that, presence of desired amount of alkali in synthesis gel promotes rapid crystallisation, opposed to huge alkali used in classical synthesis. The UV–vis diffuse reflectance (DR) spectrum of orange-red vis/ETS-10 catalyst shows complete shift of absorption edge compared to pristine ETS-10 and commercial N-doped TiO2. It was found that vis/ETS-10 catalyst showed ca. 8.79 times higher relative photonic efficiency for photocatalytic methanol reforming as compared with commercial N-doped TiO2. The observed higher photocatalytic efficiency of vis/ETS-10 catalyst might be attributed to visible light absorbing anionic species (S, C and N) and better semiconducting property of one-dimensional titanium chains within zeotype structure.

Heteroatom‐Stabilized Chiral Framework of Aluminophosphate Molecular Sieves

Intrinsically chiral: The compounds (C4H12N)2 [M2Al10P12O48] (denoted MAPO-CJ40; M=Co, Zn) were solvothermally synthesized. Their structure contains one-dimensional helical 10-ring channels enclosed by double-helical ribbons of the same handedness made of the edge-sharing of 6-rings along the 21 screw axis. The framework is intrinsically chiral and exhibits a new zeotype structure.

An easy way to achieve three‐dimensional metal–organic coordination polymers: synthesis and crystal structure of dizinc diisophthalate bis‐dimethylsulfoxide monohydrate: [Zn2(ip)4(DMSO)2(H2O)·3 DMSO]n

AbstractAn easy way of producing three‐dimensional metal–organic coordination polymers involving zinc(II) benzene‐dicarboxylates is reported. The reaction of zinc oxide with benzene dicarboxylic acids in water yielded the expected hydrated zinc dicarboxylates. These zinc compounds were then suspended in dimethylsulfoxide and heated to above 100 °C for a couple of hours; the solutions were allowed after filtration to cool down to eventually deliver crystalline compounds displaying complex zeotype structures. The crystal structure of the title compound, [Zn2(ip)4(DMSO)2(H2O)·3 DMSO]n (ipH2 = isophthalic acid = 1,3‐benzenedicarboxylic acid, DMSO = dimethylsulfoxide), is reported for the first time and shows a three‐dimensional network where octahedrally and tetrahedrally coordinated zinc atoms (present in a 1:1 ratio) are linked by bridging isophthalate ligands. The complex coordination network exhibits a remarkable channel structure along the z‐axis. The related zinc terephthalate–DMSO complex was similarly prepared and the crystal structure determination revealed an already documented zeotypic structure: [{Zn4(OH)2(tp)3(DMSO)4} 2H2O]n (tpH2 = terephthalic acid = 1,4‐benzenedicarboxylic acid). Weak interactions as well as hydrogen bonds involving water molecules and carboxy groups play a major role in the formation of these complex three‐dimensional networks. In comparison, the zinc 1,2‐benzene‐dicarboxylate–DMSO complex could not be isolated, even under more drastic conditions. The higher symmetry of the coordination network found in the zinc terephthalate–DMSO complexes was incidentally corroborated by 13C CP/MAS spectroscopy. Copyright © 2007 John Wiley & Sons, Ltd.

Derivation of an Interatomic Potential for Germanium- and Silicon-Containing Zeolites and Its Application to the Study of the Structures of Octadecasil, ASU-7, and ASU-9 Materials

An interatomic potential for Ge/Si-zeolites has been developed by fitting to the experimental properties of quartz, GeO2(quartz), and GeO2(rutile). Testing the force field by comparison of the experimental and computed structural properties of octadecasil, ASU-7, and ASU-9 shows errors within 1−2% in the cell parameters and interatomic distances. Furthermore, Ge−O−Ge angles are well reproduced and predicted to lie within the range of 130−138° as compared to the experimental values in the range 126−140°. The force field can be used for new zeotype structures containing germanium and silicon as tetrahedral atoms in order to predict structural properties, as well as the energetic stability of different Ge and Si orderings. Improved accuracy is achieved, relative to earlier force fields, through the use of different polarizabilities for the oxide ion in distinct environments.

The synthesis, characterization, and structure solution of SSZ-58: a novel two-dimensional 10-ring pore zeolite with previously unseen double 5-ring subunits.

The synthesis, structure solution, and characterization of the novel zeolite SSZ-58 are described. SSZ-58 was synthesized under hydrothermal conditions using 1-butyl-1-cyclooctylpyrrolidinium cation as a structure-directing agent. The framework topology of SSZ-58 was determined with the FOCUS Fourier recycling method. SSZ-58 possesses 12 tetrahedral atoms in the asymmetric unit of its highest topological symmetry, and to date it is the most complex zeolite structure solved from powder data. Rietveld refinement of synchrotron powder X-ray diffraction data in space group Pmma confirmed the proposed model. SSZ-58 contains layers of atoms that are linked together by double five-membered rings (D5R), or 5(2)4(5) subunits, that have not been observed before in any zeolite or zeotype structures. SSZ-58 possesses a two-dimensional channel system consisting of 10-membered ring pores that intersect to form large cavities circumscribed by 12- and 16-membered ring pores.

Chemistry-structure-simulation or chemistry-simulation-structure sequences? The case of MIL-34, a new porous aluminophosphate.

A new aluminophosphate, MIL-34, is investigated from its as-synthesized structure to its calcined microporous form. Single-crystal X-ray diffraction measurements on the as-synthesized MIL-34 (Al(4)(PO(4))(4)OH x C(4)H(10)N, space group P-1, a = 8.701(3) A, b = 9.210(3) A, c = 12.385(3) A, alpha = 111.11(2) degrees, beta = 101.42(2) degrees, gamma = 102.08(2) degrees, V = 863.8(4) A(3), Z = 2, R = 3.8%) reveal a 3-D open framework where Al atoms are in both tetrahedral and trigonal bipyramidal coordinations. It contains a 2-D pore system defined by eight rings where channels along [100] cross channels running along [010] and [110]. CBuA molecules are trapped at their intersection. (27)Al, (31)P, and (1)H MAS NMR spectroscopies corroborate these structural features. Calcination treatments of a powder sample of the as-synthesized MIL-34 indicate its transformation into the related template-free structure that is stable up to 1000 degrees C. Lattice energy minimizations are then used in order to anticipate the crystal structure of the calcined MIL-34, starting with the knowledge of the as-synthesized structure exclusively. Energy minimizations predict a new regular zeotype structure (AlPO(4), space group P-1, a = 8.706 A, b = 8.749 A, c = 12.768 A, alpha = 111.17 degrees, beta = 97.70 degrees, gamma = 105.14 degrees, V = 846.75 A(3), Z = 2) together with a thermodynamic stability similar to that of existing zeotype AlPOs. Excellent agreement is observed between the diffraction pattern calculated from the predicted calcined MIL-34 and the experimental X-ray powder diffraction pattern of the calcined sample. Finally, the atomic coordinates and cell parameters of the calcined MIL-34 predicted from the simulations are used to perform the Rietveld refinement of the calcined sample powder pattern, further corroborated by (27)Al and (31)P NMR measurements. This unique combination of experiment and simulation approaches is an interesting and innovative strategy in materials sciences, where simulations articulate the prediction of a possible template-free framework from its as-synthesized templated form. This is especially valuable when straightforward characterizations of the solid of interest with conventional techniques are not easy to carry out.

Tris(μ-1,4-benzenedicarboxylate)tetrakis(dimethyl sulfoxide)di-μ3-hydroxo-tetrazinc dihydrate

The title compound, [Zn4(OH)2(C8H4O4)3(C2H6OS)4]·2H2O, has been prepared from the self-assembly reaction of Zn(ClO4)2, NaOMe and H2bdc in di­methyl sulfoxide. The polymer exhibits a zeotype structure with microporous layers of ca 10.22 × 12.29 Å.