Designed Assemblies in Open Framework Materials Synthesis An Interrupted Sodalite and An Expanded Sodalite.код для вставкиСкачать
COMMUNICATIONS [HKh(FII,j,(lII'O,H)] inwrmetliate which has been characterized in path B :ind which I I C \ ii further 5 7 kcalmol-' lower in energy [7a]. (251 .A wnilrir coiicIusion liiis been obtained for the formation o f t h c 0 5 ixmier ot lhr: Ioriiiic ;icid [7n] (261 i i ) I. H o s o k a u x . S. I.Mui-nhashi. A C T Clirni. K I Y . 1990. 23. 49: b) A M. Joahi. H. K J;iinc\. O i , ~ ~ / i i ~ / i i r t a /19YO. / i i ~ . sY. 199: c) L. Versluis, T. Ziegler. ihid. 1990. 9. 20x5. d) I<. H Morris. lnnrfi. C k i i . 1992. 31. 1471. . S Bhandari. P. R. Rahlen. J. A m . C ' l i i w Soc. 1994. 116. 1839. Y . A. M Mehel. K . Morokuma. J. A m . C%1~11. So.. 1994. 116. 1I W J 3 iL C'Il(W?l. IYX2. Y4. 781, Arl,~L,ll. ChPIIl. In/. Ed. h f i l . [2Yj a ) I< t l ~ l l l l ~ i ~ l l lAl/i'<,li. 1YX2. ? / , 71 I : h ) 'r. A. Alhright, J. K Burdett. M H. Whangbo. Orhirul Iritcrf i ( ' i i i i i i $ oi C i i c w i . s t ~ - i - .Wile!. Kew York. 1985, pp. 352--35h. Designed Assemblies in Open Framework Materials Synthesis: An Interrupted Sodalite and An Expanded Sodalite** Pingyun Fcng, Xianhui Bu, and Galen D. Stucky* A number of new framework materials based on zinc-oxygen and phosphorus-oxygen tetrahedra have recently been characterized!" 21 some of which are structural analogs of natural zeo1ites.I" These include zeolite X and h y d r o - ~ o d a l i t ewhose [~~ structures werc established by Rietveld refinement of X-ray powder data. The synthesis of solids with zinc phosphate open frameworks can be carried out from -20 'C (zeolite X) to 200 C.I2' This composition also pushes the limits with respect to the ionic radii of the tetrahedrally surrounded atoms (T atoms) of materials with open frameworks; Zn" (0.60 A) is the largest for ;I pure (TO;'. T'OY-) phase zeolite and P5* (0.17 A) is one of the smallest ions.[41 One important aspect in the synthesis of framework materials is thc mechanism by which the inorganic framework is assembled by the templating molecule. The piperazine molecule has a number of features which can be used for such a study. The recent studies on the trioxane-templated silica ~ o d a l i t e [sug~] gest thxt the molecular dimension of the similarly sized piperazine molecule is ideal for organization of four-ring units into a cage configuration. The directed hydrogen bonding should also iinpoac at Icaat one symmetry operation of the molecule on the framework. that is. the crystallographic site symmetry should be a subgroup of the molecular point group symmetry. This is distinct froin dynamic templating in which the inorganic condensation is around a spatially averaged distribution of the orga nic molecules. In this study. we were interested in those cases in which the symmetry of host frameworks i s determined by nonframework template A complication occurs for sodalite structures when the templating molecules are not only ordered but also hxve a charge less than +3, as required to balance the charge of a sodalite cage with ( T 3 + / T 4 + )or (T2+:T5+) composition. We describe here two mechanisms by which the negative charge of the framework is lowered to match that of guest molecules while preserving the sodalite type cage linking: cage interruption and expansion as discovered in two newly synthesized [*] Prof. D r G L). Stucky. P. Feng. D r X. Bu C'Iieini\lry 1)eparttneiit. University ol'California d t Santa Bai bara Santn U:irhal-a. C A 93106 (USA) 1cIet':i~~l r i f code (805]893-4120 e - m a i l : \tuck y o shxray.tic5h.edu + [**I Ihi\ rcsciircli was supported ( i r a i i l I ) M K 93-08511 in part by the National Science Foundation under zincophosphates. The cage interruption mechaniam involves the removal of a tetrahedrally coordinated atom from the sodalite cage which reduces the negative charge froin - 3 to - 1 per cage. The cage expansion mechanism involves the insertion of tetrahedral atom groups into the sodalite cage, which reduces the cage charge from - 3 to -2 per cage. In both cases, the symmetry of template molecules (inversion center and twofold axis of piperazine molecule, respectively) plays a structure-directing role i n the formation of the new cage assemblies. Crystals of ZnPOiPPZ' (zincophosphate with a monoprotonated piperazine) were grown by "nonaqueous" synthesis from a mixture of Zn(N0,)2 6 H,O. H,PO,, ethylene glycol, and piperazine. The molar ratio of the corresponding precursor oxides (ZnO and P20,), piperazine, and ethylene glycol was 1.0:0.96:0.91 : 2 5 . The gel was stirred at room temperature for about 30 minutes. The mixture was heated at 17O'"C for four days in a teflon-coated steel autoclave. The product was recovered by filtration and washed with deioniad water. Clear needlelike crystals of typical dimensions 0.3 x 0.1 x 0.2 mm3 were obtained, which were suitable for an X-ray structure analysis (Fig. 1 a). ?(la! cl Fig 1 . Crystal structures of a ) ZnPO.'PPZ+ and b) ZnPOsPI'L' ' : ORTEP views of zinc and phosphorus tetrahedra. A t o m labels having "a" mii "b" refer to syinmetry generated atoms. Crystals of ZnPO/PPZ2 (zincophosphate bvith a diprotonated piperazine) were grown from a mixture of Zn(NO,), . 6 H 2 0 , H,PO,, H,O, and piperazine. The molar ratio of the corresponding precursor oxides (ZnO and P20,). piperazine, and water was 1.0:0.95:0.89:85.A white gel was formed at an approximate pH of 3 after stirring the mixture for about 15 minutes. The mixture was heated at 170 ' C' for four days i n a teflon-coated steel autoclave. The product was recovered by filtration and washed with deionized water. Clear platelike crystals of typical dimensions 0.20 x 0.17 x 0.03 mm3 were obtained. which were suitable for an X-ray structure analysis (Fig. 1 b ) . + COMMUNICATIONS ZnPO PPZ' has an interrupted sodalite-type structure which obtained by removal of a T dtom ( Z n z +in this c'ise) from sites ielated by one of the three twofold axes through opposing fourlings of the normal sodalite c'ige structure (Fig 2a and 3 '1) One piperazine molecule per cage. whethei mono- or diprotonated. is unable to provide the three positive charges which are needed to balance the negatively charged framework of dn uninterrupted zincophosphate sodalite structure The charge compensation is achieved instead by removal of one lower charged T atom (Zn") for every six T atoms, and the addition of four piotons, which form hydi-oxyl groups with oxygen atoms f o r a net charge gain of + 2 per cage The remaining - 1 charge on the edge is b'ilanced by one monoprotonated piperazine molecule loc'itcd at the center of the cage ZnPO PPZ2+ has an expanded sodalite structure with eight eight-rings instead of six-rings (Figs. 2c and 3 b) The structural relationship between the expanded sodalite and the normal sodalite is described below Starting with a normal zincophosphate ~ o d n l i t e ' ~edge ] ([Zn,,P,z0,,]'2~). oriented such that is there die four four-rings on the equatorial plane, one four-ring 'ihove and one four-ring below (Fig 2 b), a hypothetical exp'inded structure can be derived by rotation of the top and boltom four-rings by 90 followed by iiiaertion of four ZnO(H,O), units and four PO(OH)Z units into eight T-0-T connections between the four equatorial four-rings and two four-rings above m d below This gives a stoichiometry of [Zii,2P,20,,]'2[Zn,P,O,(H,O),(OH),]jt which is identical to the observed one. but with two water molecules coordinated to e x h of the foui inserted zinc atoms and two OH groups coordin'ited to each of the inserted four P atoms In the actual stiucture (Fig 2c) one of the two w'iter molecules on each 7inc and one of the two OH groups o n e d i phosphorus i n the 'ibove hypothetical structure are distributed onto zinc m d phosphorus ,itoms 'icross the eight-rings This gives rise to the sodalite-type cage liiik'ige with elongated cages s h m n g single four-rings or single eight-rings (Fig 3 b) The reduction of the negative charge froin - 3 for 'I normal sodalite cage to -2 for an expanded cage is achieved with the introduction of one PO(0H): unit per cage The unit cell volume of ZnPO PPZ' is 1403 8(7) A' which is slightly more than twiFe the cell volume of 688 01(3) A 3 for the normal zincophosphate sodalite 13] This is consistent with four interrupted ccigesper unit cell The volume increclae per cage over the normal sodalite is only 2 0 % which suggests that the dimension of the template molecule is ideally suited for such a four-ring 'issembly In contrast. the volume increase per cage is as large as 53 7 % for ZnPO PPZ2+ due to the cage elongdtion This extrn \pace inside the cage is t Zn c ep a3 @? 9 (* O& I/ C (4 (b) (4 t i g 1 d) The intcirupted \od,ilite ~ i g ~e i t l the i rempl i t e moleculc loc,itcd oii the i i i ~ c r \ ~ ocentcr ii .it the L I ~ L C e n t u hi the iiorindl ,iluinino\ilic~itc~od,iliteu g e c ) the cxpmdctl wd'ilite cdpc wilh the pipet L i ~ i ~ i dic,itwn ~u~ii m d w'ttet iiioIc~uIco n the tuotold < i u dround the lnverslon center on Which I ig i I l l u w . i t i o n 01 the frmieuol k \ I I L I L ~ U I L m d soddite tqpc cdgc Iink'tge Foui inteitupted sod.il~tec ~ g e siliriiitig vngle I O U I i l ne\ there x c 110 h i \ 11ng\ due 10 the T litotii teiiimdl h) f o u i eupmded \od,ilite L,ige\ >hztitiigsuiglc lour chair conform'ition of the piperazine molecule h a e n point symmetry of 2 171 with three individual syniinetry elements ( I , 2, m ) , the template molecule therefore imposes its individual symmetry constraint oilto both types of frdineuork structures In the expmded cage, the symmetry mntch I F 'ichieved between the fr'imework 'ind two different template molecules, piperazine and w'itei In both structures. the symmetry information of the teinpl'ite molecule is passed onto the framework mainly through guest fr'iinework hydrogen bonding a s illustiated in Figure 4 In ZnPO PPZ', the extra proton in the piperazinium monocation is statisticdly distributed on two nitrogen sites Each template 0 bond to one of four nitrogen 'itom forms 'it least one N - H four-rings and inay h a w another N - H 0 bond depending on whether the extra pioton i s located on it (Fig 4 a ) This observ'itioii is in contrdst with the results with trioxane silica soddite i n which the guest framework hydrogen bonding mny only involve the weak C -H 0 interactions due to the Lick of OH groups m d the trioxane molecule is orieiit'itionallq disordeied lo preserve the cubic 5yi11inetr> Of the I Ill$?\ cage ''1 t ' (4 'I) 6 * * (b) COMMUNICATIONS (4 (b) In ZnPO 'PPZ". one bridging oxygen atom from each of the four equatorial foul--rings forms the N-H . 0 type bonding to each of the hydrogen atoms on NH, groups of piperazine molecules (Fig 3 b and 4 c ) . All four participating oxygen atoms are on the same side of the four four-ring cluster due to the symmetry constraint imposed by a twofold axis. This is different from ZnPWPPZ where four participating oxygen atoms are divided on the two sides of the cluster formed from four four-rings, an arrangcmenl consistent with the center of inversion. The hydrogen bonding between Zn(H,O) groups and extra-framework H Z O molecules gives OH, tetrahedra (Fig. 4c). As shown in Figure 4, the molecular dimension of the piperazine inoleculc and the 90' ,'I80 distribution of hydrogen atoms on the t i 4 0 nitrogen atoms make piperazine ii perfect molecule for the orgunimtion of four four-ring units. In ZnPOiPPZ', thcsc I'our Ihur-rings units share single four-rings to form layers that arc interconnected into the three-dimensional sodalite type framework by bridging bidentate -O-P(OH),-O- groups (Fig. 3 a ) . Similar layers are also found in ZnP0:'PPZ' ' (Fig. -3 b ) , Both structures contain interruptions between tetrahedrally suri-ounded atoms. Due to the charge difference of the piperiizinc molecules in the two structures as well ;IS the inclusion of a water inolecule in the expanded structure, the style of interruption i s different. leading to two unique novel cages assemblies. However. the) are similar to each other in that the cages are interlinked in a manner analogous to that of sodalite. The interruption of the framework structure is one of the key structural featurcs for se\eral zincophosphates"' as well as aluminophosphates.lHl I n the cases discussed herein it helps to reduce the negativc charge on the framework. The xynimetry matching between the inorganic host and template molecules are not limited to purely tetrahedral zincophostcms ;IS described above. Recently. we discovered a new piperaline-teinplated vanadium(rv) phosphate (space group: C ' I I I ) in which the syinnietry of the tetrahedral-octahedral framework is determined by the mirror- symmetry of the tcmplate nioleculc.~ylIn this structure both two-centered and three-centered hydrogen bonds are used to direct the assembly of the vanadiiim(rv) phosphate into an extended array. I n concluhion, we have demonstrated that all three individual symmetry elements of a piperazine molecule can direct framework liirination and that partial zeolite-like cage structures can be 5 ) nthcsirod by using a template design strategy. The results are important for the elucidation of the synthesis mechanism of sodnlite-hoscd zeolite inaterials in general and indicate that in future i t may be possible to derive a strategy for the design of new I'rmneuork structures as well as modification of existing types utilizing template symmetry, charge matching. and directed hqdrogcti bonding between guest and host. This strategy Fig. 4. Gucst-fi-;ime\bork hqdi-ogen bonding. :I) ZnPO: P P l t . monoprotonated piper:irinium s l i o u i i 'is di-pimtoiiated due to its s l a t i s t i c i i l dictrihution o n llic t w o sites: h) ZnPO:PPZZ +.top view of thc four qu,itorial four-rings showing host. guest hqdrogcn bond\ hetwccn pipcrarine N H , groups and framewnrk cxy:cii iitoiiii: c ) LnPO PPZ' ' . side view of the four cquatoriiil four-rings shouing host euest hvdroren bonds be1uccn exirr,i-l'rameaork H 2 0 and H,O o n Zn tetrahedra iii tlic Inner portion oftlie cage. (c) should apply to both interrupted and noninterrupted zeolitic systems since the directed hydrogen bonds described above are between the bridging framework oxygen atoms and piperazine molecules. Rccci\cd: N w c i n b e r 3. 1994 Re\,ised version' March 17. 1995 [Z 7451 IE] German version .Aii,yeii. U7ciii. 1995. 1/17. 1911 1911 ~ Keywords: hydrogen bonding . sodalites . solid-state structures . template syntheses . zeolites [IJ R. H. Jones. J. Chen. G. Sanknr, J M . Thomas i n %rw/ii(,r id R[~/rii(~r/.I.li(~ni/i1. Weitkaiiip. H. ti. K x y r . H. l'lbifcr. ',V. Holdei-ich). Elsevier. Amsterdam. 1994. p. 2229.  T. E. Gier. G. D. Stuck>. ,Voitiir.c ( / , o i i r / o i i ) 1991. 349. i i l X . 131 T. M Nenoff, W. T. A. Harrison. T. E . Gier. Ci D Stuchy. .I .AIII. ( ' / i o i i . S o ( . 1991. il.7. 37x. 131 T M Nenol'f. W. T. A. Harrison. T.E . Gier. N . L Keder. C. M. Z,ireinhii. V 1. Srdano\.. J. M . Nicol. G. D. Srucky. Inor-c.. C ' / W I > . 19Y4. 33. 2472.  K.Futterer. h' Depmeier, F;. Altorfcr. P. Behren5. 1. t.clschc. Z. hr.,i/ri//o,q,-. 1994. 2OY. 517. [(I] W Depmcier. Z. Ar.i\/d/o-c.r.. 1992. i Y 9 . 75.  W.T. A. Harrison. T. E. Martin. T. E Gier. G D. SttiLkb. .I ,Mnrt.r.. C ' / i w i i . 1992. 2. 175. 0 Huo. R. Xu. S Li, Z. Md. J. M . Thomas. I<. H. .lono. ,A M.Chippindale. J. C,/icin. S I X . C/7<vil.Coiiiniiit!. 1992. 875. [Y] X. Ru. P. Fens. G . D. Stucky. .I C / ~ ( WSo(. ? . < ' / i u i i , ~ ' ~ J I ~ I I I ~ uin/ I .press. . [S] [lo] a) Crkstal data for ZnPO PPZ': [ Z I ~ , ( P ~ , ] ( H ~ P O , J ~ ] ( C , H , N ? H,\I, ) .= 306.9. space group C2:<,. [I = 13.370(41. /I = 12.X3i4). 1 = 8.20713) A, - 94.79(1) . I ' = 1402.8(7) A'. I = 4. J I ~ , , , ~ ,= , 7.40 gciii I . cnlorless needle. tal si7e0.2X x 0.10 x 0.07 mill3. Mo,,. j . = 0 71071 .A ciil 'ibwrption cnrrection. lilln= 0.56. I,,,,l, = 0.SO. 1 11 R = 0.061 for 11s parameters and 1587 iiniqiic retlcc h ) ('rystiil d i i t d for ZnP0:PPZ" : [Zii(HLO)Zii(PO,)(HPO,)], (H,O) (C,H,N,H,).- LI =785.61. space proup C : c . ( I = l2.!l93(7j. /J = 14.X97(8). < = ll.X49(6)A./j = 97.821(3). i = 2115i21 A'./ = 4.1'. ,,.,,= ?..ihXgcm-'. colorle\\ plate. crystal m e 0.20 x 0.17 x 0.0.3 inin'. \lok,. I = 0.71073 A. 11 = 4.99 n n n - ' . einpirical ;ibsorption corrcctioii, I;,,,,, = 0 (I,,,,,< = 60 . R = 0.049. I I R = 0.00 for I91 parainctct-s ;iiid 24 tinns with I > 3 u(/).c i Further details ofthe crystal striicturc investigation are ;i\ailabls on request l'rom tlir Dii-ector of the C;iinbridge Data Centei-. I ? L ' i i i o n Road. GB-Cxmbridge CtlZ 1 EL ! i J K ) . 011 qiiotiiig the toll journal cit'itinn.