Richard M. Kirchner

The structure of as-synthesized AIPO4-16 determined by a new framework modeling method and Rietveld refinement of synchrotron powder diffraction data

Synchrotron powder data on as-synthesized AIPO4-16 was indexed on a cubic cell with a = 13.3832(6) A and systematic absences of hkl with h + k, h + I, k + I = odd and hhl with h + l = odd. The most probable space group is F23 (#196), assuming alternation of the aluminum and phosphorus atoms. The framework topology was confirmed using a new “a priori” modeling method presuming the idealized space group Fm ovbar3 m (#225) with 40 chemically equivalent tetrahedral atoms per unit cell. The resulting framework topology is equivalent to J.V. Smiths theoretical net #214 and can be described as an idealized zunyite framework with complete tetrahedral occupancy, as originally proposed by D.W. Breck. This new framework topology (designated AST) is the third molecular sieve topology that is built from double 4-rings. The cavities contain the organic template, quinuclidine, which was successfully modeled as a disordered group. The largest pore opening is a 6-ring. The final Rietveld residuals are R(wp) = 0.192 and R(F) = 0.106.

The structure of calcined ALPO4-41: A new framework topology containing one-dimensional 10-ring pores

Abstract Synchrotron powder data for calcined never-rehydrated AlPO 4 -41 were initially indexed on a C-centered orthorhombic cell. Possible systematic absences suggested a c -glide plane perpendicular to a . The structure was determined by model building in the idealized space group Cmcm (ignoring Al,P alternation). The new framework topology (designated “AFO”) consists of layers of 4.6 2 . 4.10-rings that are connected by UDUD chains, similar to the UDUD chains in AlPO 4 -5 (AFl), -8 (AET), -11 (AEL), -25 (ATV), -D (APD), and -54/VPl-5/H1 (VFl) and -H2. The widest pore in AlPO 4 -41 is a distorted elliptical one-dimensional 10-ring channel that is slightly larger than the 10-ring channel in AlPO 4 -11, consistent with observed sorption properties. A full-pattern Rietveld refinement assuming alternation of Al and P in space group Cmc 2 1 gave R (wt. profile) = 0.273 and R(F) = 0.087. However, the fit between observed and calculated profiles was not satisfactory, nor were distances and angles involving atoms on the mirror plane. Removal of the mirror planes suggested various monoclinic space groups, which were evaluated by a DLS refinement of the alternating Al,P trial model in a properly transformed cell. The lowest DLS R factor (= 0.00045) was obtained in P 2 1 . A Rietveld refinement in space group P 112 1 gave R (wt. profile) = 0.164 and R(F) = 0.074 with refined cell parameters a = 9.7180(1), b = 13.7915(1 ), c = 8.3591(1)A˚, andγ = 110.59(1) ∘ . The agreement between experimental and calculated profiles and the mean values for Al O and P O distances and Al O P angles are acceptable. The differences between the idealized orthorhombic structure and the monoclinic structure are described. Solid-state 27 Al and 31 P MAS n.m.r. spectra show a single tetrahedral site for Al and for P and do not distinguish between monoclinic or orthorhombic symmetry.

The structure of calcined AIP4-31: A new framework topology containing one-dimensional 12-ring pores

Abstract Synchrotron powder data on a calcined never-rehydrated AIPO 4 -31 sample were indexed on a hexagonal cell with a = 20.871(1) and c = 5.003(1)A . The structure was solved by model building in the idealized space group R 3 . the framework topology of AIPO 4 -31 consists of very nonplanar layers of 4 3 . 6 2 · 12-rings approximately perpendicular to c . The 4-rings constitute three columns parallle to c that are related by three-fold symmetry. The 4-ring planes in every other column are displaced by cl 2 from each other. In addition, each of the three unique columns has a different tilt of the 4-ring planes. The 6-rings result from zigzag chains parallel to c , which linke the staggered 4-ring columns. Projections parallel to c show nonplanar layers consisting only of 6-rings. The surface lining of the unidimensional 12-ring pores consists of a 6-ring “wrap”, where one set of parallel edges of each 6-ring is perpendicular to the pore direction, as in cancrinite. The AIPO 4 -31 structure is a new framework topology, designated “ATO”. The largest pore opening in AIPO 4 -31 (a circular 12-ring) is smaller than the circular 12-ring pore present in AIPO 4 -5, consistent with the observed sorption properties. A Rietveld refinement gave R (wt profile) = 0.173 and R ( F ) = 0.86.

Synthesis, characterization and structure of SAPO-56, a member of the ABC double-six-ring family of materials with stacking sequence AABBCCBB

Summary Three small pore (8-ring) structures have been synthesized using N,N,N′,N′-tetramethyl-1,6-hexanediamine (TMHD) as the structure-directing agent, AIPO-17 or SAPO-17 (ERI), MAPSO-34 (CHA) and a new structure, designated SAPO-56. Synthesis conditions and gel composition influence the structure-type formed. SAPO-56 adsorbs oxygen, nitrogen, and normal paraffins but not isoparaffins, and has a pore volume comparable to SAPO-34 (CHA). Synchrotron x-ray powder diffraction, electron diffraction, and MAS-NMR were used in conjunction with model building to solve the structure. The SAPO-56 structure, a member of the ABC six-ring family, contains only D6R units (like CHA and AFT), arranged to give gmelinite cages (GME) and large cages (AFT) previously observed in AIPO-52.

The structures of as-synthesized AlPO4-53(A), calcined dehydrated AlPO4-53(B), and AlPO4-53(C), a new phase determined by the FOCUS method

Abstract AlPO 4 -53 was synthesized hydrothermally with methylamine as a structure-directing agent. The structure of as-synthesized AlPO-53(A) was solved using AlPO-EN3 as a starting model. The Rietveld refinement converged ( R P = 0.140) in space group P2 1 2 1 2 1 ( a =10.3212(1) A, b =13.6308(1) A and c =17.4539(1) A) for unit cell composition: Al 24 P 24 O 96 ·8.5CH 3 NH 2 ·14H 2 O. AlPO-53(A) is isotypic with as-synthesized AlPO-EN3, JDF-2, UiO-12-as, and presumably CFSAPO-1(A). The structure of calcined dehydrated AlPO-53(B) was solved by direct methods, and refined to R P =0.084 in Pbca ( a =18.0241(1) A, b =13.9174(1) A and c =9.6554(1) A). The topology of AlPO-53(B), the tetrahedral equivalent of AlPO-EN3, is iso-structural with MCS-1 and UiO-12-500. This topology (structure type code AEN) has two 8-ring channels that intersect to form a 2D system. Heating AlPO 4 -53 to 700°C yields a new condensed phase, AlPO-53(C). The structure of AlPO-53(C) was solved with the FOCUS program and refined to R P =0.124 in C121 with a =16.4440(4) A, b =5.1075(1) A, c =13.4846(4) A, and β =88.259(1)°. AlPO-53(C) has a new topology described as brw nets in the ac plane, linked by single and double zigzag chains, parallel to b . The elliptical 8-ring pores, parallel to b , produce a 1D channel system. The highly distorted 4-, 6-, and 8-rings in AlPO-53(B) become more regular in AlPO-53(C). The thermal transformation of AlPO-53(B) to AlPO-53(C) is illustrated.

Structure refinement, electron microscopy, and solid-state magic angle spinning nuclear magnetic resonance characterization of AlPO4-52: An aluminophosphate with a large cage

Abstract Synchrotron powder X-ray diffraction (PXRD) data for calcined AlPO 4 -52 were refined in space group P 3 1c using the Rietveld method. The previously proposed topology (AFT), an ABC six-ring structure type with an AABBCCAACCBB stacking sequence, was confirmed. The refined unit cell dimensions are a = b = 13.715 (1) A and c = 29.676 (3) A. Possible causes for peak broadening in the synchrotron PXRD profile were examined. A series of PXRD patterns obtained at various temperatures indicated that the calcined sample used for synchrotron PXRD was partially rehydrated. Electron diffraction patterns showed particle texture effects but no evidence for faulting or disorder. Individual crystallites of AlPO 4 -52 are roughly equidimensional hexagonal prisms. Preferred orientation of the crystallites was not evident. Solid-state magic angle spinning nuclear magnetic resonance (MAS n.m.r.) spectra of calcined never-rehydrated AlPO 4 -52 showed that all aluminum and phosphorus atoms were tetrahedrally coordinated. However, MAS n.m.r. spectra of a calcined rehydrated sample showed a 1:2 ratio of tetrahedral to octahedral aluminum atoms due to extraframework water coordination. The 31 P MAS n.m.r. spectra are consistent with phosphorus atoms located exclusively in double six-rings.

The synthesis and properties of binuclear pentacyanoiron(III)-μ-cyano- amminetetracyanoiron(III) [(C6H5)4P]4[(NC)5FeNCFe(CN)4NH3]·6H2O

Abstract The binuclear cyanoferrate, tetraphenylphosphonium pentacyanoiron(III)-μ-cyano-amminetetracyanoiron(III), [(C6H5)4P]4[Fe2(CN)10NH3]4−, was synthesized by air oxidation of aqueous solutions of Na3[Fe(CN)5NH3] · 3H2O. Single crystal X-ray diffraction studies show the compound to contain the binuclear, cyano-bridged anion, [(NC)5FeNCFe(CN)4NH3]4−. This compound is structurally identical to the one prepared by A. Ludi et al., [Inorg. Chim. Acta, 34, 113 (1979)], with the exception that [Fe(CN)6]3− is not required for the synthesis of this compound. The Fe(III) atoms are antiferromagnetically coupled through the CN− bridge, as shown by a maximum in the magnetic susceptibility at 50 K. The electronic and IR spectra of the complex in the solid state and in solution are discussed.

Structures of the K+ and NH4+ forms of Linde J

The aluminosilicate zeolite Linde J has a unique topology. The structures of the K{sup +} and NH{sub 4}{sup +} forms of Linde J ([X{sub 2}(H{sub 2}O)][Si{sub 2}Al{sub 2}O{sub 8}] where X = K or NH{sub 4}) are identical except for slight cell size and positional differences due to NH{sub 4}{sup +} being larger than K{sup +} cations. The space group is P2{sub 1}2{sub 1}2{sub 1}. Cell dimensions are: K{sup +} Linde J, a = 9.4577(2) {angstrom}, b = 9.5573(2) {angstrom}, c = 9.9429(2) {angstrom}; NH{sub 4}{sup +} Linde J, a = 9.6324(4) {angstrom}, b = 9.6423(3) {angstrom}, c = 10.0230(3) {angstrom}. Zigzag 8-ring channels intersect giving a 2-D pore system.The aluminosilicate zeolite Linde J has a unique topology. The structures of the K{sup +} and NH{sub 4}{sup +} forms of Linde J ([X{sub 2}(H{sub 2}O)][Si{sub 2}Al{sub 2}O{sub 8}] where X = K or NH{sub 4}) are identical except for slight cell size and positional differences due to NH{sub 4}{sup +} being larger than K{sup +} cations. The space group is P2{sub 1}2{sub 1}2{sub 1}. Cell dimensions are: K{sup +} Linde J, a = 9.4577(2) {angstrom}, b = 9.5573(2) {angstrom}, c = 9.9429(2) {angstrom}; NH{sub 4}{sup +} Linde J, a = 9.6324(4) {angstrom}, b = 9.6423(3) {angstrom}, c = 10.0230(3) {angstrom}. Zigzag 8-ring channels intersect giving a 2-D pore system.

Synthesis and Idealized Topology of AIPO4-52, a New Member of the ABC Six-Ring Family.

The novel aluminophosphate molecular sieve AIPO 4 -52 has been synthesized via stirred reaction at 150°C of an aluminophosphate mixture containing both tetraethylammonium hydroxide (TEAOH) and tripropylamine (Pr 3 N). The sorption characteristics of the calcined material are consistent with a pore structure controlled by 8-rings. The cell dimensions are a = 13.73°. c = 28.95a and γ = 120°. The systematic absences, hhl for 1 = 2n, indicate a c glide plane. The idealized symmetry is P31c. The AlPO 4 -52 topology is a new member of the ABC six-ring family(ref. 1) of structures. It has the longest known repeat sequence (12 layers) described as Aabbccaaccbb. The structure contains three different cages all with 8-ring windows. The cages are a gmelinite cage, a chabazite cage, and a new cage previously described as 8 * 3(2.4.6)(ref. 2) but now referred to as an AIPO 4 -52 cage.

Direct methods structure determination from synchrotron powder diffraction data of a new clathrasil, TMA silicate

Abstract The structure of as-synthesized TMA Silicate, an aluminosilicate synthesized with the tetramethyl ammonium (TMA) structure directing agent, was solved using intensities extracted from high-resolution synchrotron powder diffraction data and ab initio direct methods. The trial topology was improved by DLS refinement, and the structure was confirmed by successful Rietveld refinement. The space group is C2/m, and lattice parameters are a = 13.35211(14) A ; b = 13.05531(12) A ; c = 12.53013(13) A ; β = 113.285(1) °. The framework topology of as-synthesized TMA Silicate consists of 4-connected T-atoms in 4-, 5-, 6- and 8-rings. Two types of cages are interconnected by pores no larger than 6-rings. The larger cage is a peanut-shaped 30-hedron [485126108] that is the fundamental polyhedral building unit. The three-dimensional structure results from sharing the 4-, 5- and 6-ring faces between adjoining large cages. The three-dimensional structure also contains a smaller 10-hedron cage [445462]. Both cages have crystallographic 2/m site symmetry. Tetramethyl ammonium cations are located in each lobe of the peanut-shaped cages. Because the largest opening to any cage is through 6-ring pores, which are too small to let the TMA pass, as-synthesized TMA Silicate can be classified as a clathrasil.