NCHU-3: A Crystalline Inorganic-Organic Hybrid Molecular Sieve with Extra-Large Cages

Inorganic–Organic Hybrid Materials

NCHU-3: A Crystalline Inorganic–Organic

Hybrid Molecular Sieve with Extra-Large

Cages**

Ching-Yuan Cheng, Shu-Juan Fu, Chia-Jung Yang,

Wei-Hung Chen, Kuan-Jiuh Lin,* Gene-Hsiang Lee, and

Yu Wang

Since the discovery of aluminophosphate VPI-5,

_the

syn-thesis of new crystalline large-pore zeolite-analogue materials

with diameters of larger than 10! has been an important goal

because of the diverse applications of these materials as

nanoreactors, biosensors, and in nanotechnology.

Consid-erable attention has been directed towards the associated

inorganic–organic hybrid architectures that, because of the

incorporation of organic functional groups within a solid state

inorganic framework, promise access to an even wider range

of applications, such as altering the expected shape-selective

influence in molecular sieves and hydrocarbon

transforma-tions.

_{To date, however, relatively few examples of}

well-ordered crystalline solids with both large and hybrid pores are

known.

_{Herein, we describe a novel nanoporous}

organo-phosphonate that contains both vanadium and gallium

centers, [Ga

(VO)

K

(OH

)

(C

H

P

O

)

(H

O)

], which we

have called NCHU-3 (National Chung-Hsing University-3).

Pale-blue crystals of NCHU-3 were grown from a reaction

mixture of KOH, Ga

O

, V

O

, ethylenediphosphate, and

[*] Prof. K.-J. Lin, C.-Y. Cheng, S.-J. Fu, C.-J. Yang, W.-H. Chen Department of Chemistry

Nanocenter, National Chung-Hsing University Taichung 402, Taiwan (Republic of China) Fax: (+ 886) 4-22862547

E-mail: [email protected] G.-H. Lee, Prof. Y. Wang Department of Chemistry National Taiwan University

Taipei 106, Taiwan (Republic of China)

[**] We thank H. S. Sheu at synchrotron radiation research center for technical assistance with PXRD data. This work was supported by the National Science Council of the Republic of China (NSC 90-2113M-005-013) and the Institude of Chemistry, Academia Sinica. Supporting information for this article is available on the WWW under http://www.angewandte.org or from the author.

Angewandte

Chemie

1981

water in molar ratios of 1:1:2:6:2220heated at 20

08C for

72 hrs in a 23 mL teflon-lined stainless steel autoclave. The

structure of NCHU-3 was determined by single-crystal X-ray

analysis (Figure 1). The orthorhombic structure has an open

framework with multidimensional channels. The asymmetric

unit of the framework contains one gallium-centred

tetrahe-dron (Ga O bond lengths: 1.800(8) (; 2) and 1.805(5) !

(; 2), two crystallographically distinct octahedral oxovanadyl

centers (V

O

(OH

): 1.612(2), 1.977(8) (; 2), 2.036(8) (; 2),

and 2.290(17) !; V

O

(OH

): 1.575(15), 1.961(8) (; 4), and

2.45(3) !; the bond valence sum of vanadium is 4.0and 4.4,

respectively),

_{and two ethylenediphosphate groups. Each}

phosphorus atom in ethylenediphosphate is tetrahedrally

coordinated, that is, the two O

PC tetrahedron of [O

P

CH

CH

PO

]

share the carbon atoms with the ethylene

groups. The secondary building blocks of NCHU-3 are

described in terms of 4-, 5-, 6-, and 16-rings, which are

combinations of 4, 5, 6, and 16 polyhedrons, respectively.

Interestingly, NCHU-3 consists of multidimensional channels

system with 6-ring apertures and 16-ring apertures, in which

the pore sizes are 5 ! ; 7 ! and 5 ! ; 14 !, respectively.

These channels intersect at the center of a chinese-vaselike

cage consisting of 63 atoms (six 6-rings and two 16-rings,

Figure 1 c and 1 d). The cage measures 11 ! ; 13 ! ; 14 !, as

measured between oxygen atoms by using the positional

coordinates of NCHU-3. Another important feature of the

NCHU-3 structure is the hydrophobic -CH

moieties covering

the walls of the Chinese-vaselike cages. The approximate

vase-void volume is 1359 !

_{per unit cell. Microporous}

materials are often compared by framework density (FD,

number of density of tetrahedral atoms per 1000 !

_).

_The

smaller the FD value, the larger is the available space in the

crystal. The FD generally decreases with increasing numbers

of 4-rings. NCHU-3 has eight 4-rings per cage, for which the

FD is about 9.3 (tetrahedrally surrounded Ga and P atoms)

and 12 (which takes into account the V atoms with octahedral

coordination) compared with the very open faujasite (12.7)

and cloverite (11.1).

The key feature of NCHU-3 rests on the extra-large

hydrophobic cages, which are occupied by free water

mole-cules and highly disordered K

_{ions. Essentially, complete}

replacement of K

_{by NH}

4+

ions by using saturated NH

Cl

solution was easily accomplished, as confirmed by

energy-dispersive X-ray fluorescence analysis. To examine the

thermal and structural stability of this open framework,

thermogravimetric analysis (TGA) and in situ synchrotron

powder X-ray diffraction (PXRD) analysis were carried out.

The TGA reveals that the water guest molecules were

Figure 1. Molecular structure of NCHU-3. a) The framework structure of NCHU-3 view down thec axis showing vaselike channels in projec-tion. b) Polyhedral view of a section of vaselike cages. (GaO4: green

tetrahedron; VO5(OH2): blue octahedron; PO3C: red tetrahedron;

CH2P2: yellow tetrahedron). c) Ball-and-stick representations of the

largest cavityconstructed from 16-rings excluding tetrahedrallycoordi-nated C atoms. d) Projection of vaselike cages along thea axis (C, H, and O atoms are omitted for clarify) showing the additional 4-, 5-, and 6-rings and Chinese vaselike void volume of 1359 G3_.

Figure 2. In situ PXRD patterns for NCHU-3 (synchrotron radiation, l = 1.32633 G). The sample was initiallyheated to 200 8C and then cooled to 40 8C in air. a) Simulated diffraction patterns on the basis of the single-crystal structure. Diffraction data recorded b) at room tem-perature, c) at 200 8C, and d) at 40 8C.I is the X-rayintensity(arbitrary units).

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liberated below 200 8C, which corresponds to a weight loss of

14 %. No weight loss was observed in the temperature range

of 200–550 8C. The simulated diffraction pattern based on the

analysis of a single-crystal X-ray structure (Figure 2 a) is in

good agreement with the PXRD pattern obtained for

NCHU-3 (Figure 2 b), which indicates that NCHU-3 is a

pure phase. The NCHU-3 sample was initially heated to

200 8C (Figure 2 c) and then cooled to 40 8C (Figure 2 d), both

diffraction patterns show that the positions of the most

intense lines remain unchanged relative to the unheated

sample of NCHU-3. The good agreement between PXRD

patterns demonstrates that the open-framework was retained

even after the loss of water molecules. Given the thermal and

structural stability of the open framework, the presence of

vacant cages in NCHU-3 affords a natural affinity to absorb

aliphatic and aromatic molecules reversibly. A TGA study

reveals a reversible aniline sorption cycle in the pores of

NCHU-3 (see Supporting Information). The framework,

which features redox oxovanadyl centers, provides an

inter-calation host for lithium ions.

_{Some preliminary reversible}

cycling data are presented in Figure 3. The cyclability of the

cell was over 200 cycles between 3 and 5 V, which indicates

that lithium ions and electrons can be removed and reinserted

into the NCHU-3 host. This result demonstrates that

NCHU-3 is scientifically interesting and potentially attractive

as a new cathode material for rechargeable lithium

batter-ies.

_{Further measurements of capacity are in progress.}

In conclusion, we present the synthesis and structure of

the first multidimensional, intersecting, large-pore hybrid

organo-phosphonate molecular sieve. NCHU-3 is novel not

only in the unusual shape of its cages with hydrophobic walls,

but also in its framework featuring redox-active oxovanadyl

centers. The above results may provide new developments in

separation, catalytic, and nanoelectronic applications.

Experimental Section

NCHU-3: A reaction mixture of V2O5(0.0909 g, 0.5 mmole),

ethyl-enediphosphate (0.2850 g, 1.5 mmole), Ga2O3(0.0468 g, 0.25 mmole),

KOH (0.25 mL, 10 m), and H2O (10mL) was sealed in a 23 mL

teflon-lined stainless autoclave, heated at 200 8C for 72 h, then cooled to 70 8C at 9 K h1_{. The resulting blue crystals were isolated by filtration,}

and washed with deionized water. Yield 0.046 g (34 % based on Ga2O5), and the synthesis was highly reproducible. Crystallography:

The X-ray diffraction low-temperature (120K) data were collected

on a CCD Bruker AXS SMART-1000 diffractometer with mono-chromated MoKa(l = 0.71069 !) in the w/2q scan. The structure was

solved with SHELXTL PLUS and refined with SHELXL-93 on F2_by

full-matrix least-squares methods. The highly disordered potassium ions and water molecules could not be completely located in the structure analysis. The induction-coupled plasma-mass spectrometry and energy dispersive X-ray analysis both showed the compound contained K, Ga, V, and P in approximately constant proportions. Ga2(VO)3K2(OH2)3(C2H4P2O6)4(H2O)13, Crystal size 0.18 ; 0.06 ;

0.06 mm, Orthorhombic system, space group Cmcm, a = 16.6870(2), b = 14.7395(3), c = 17.5737(3) !, V = 4322.4(1) !3_{, Z = 4, 2V}

max=

558; R1=0.101, wR2(F2) = 0.278, and GOF = 1.113; residual electron

density between 3.6 and 1.81 e !3_{. CCDC-195599 contains the}

supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+ 44) 1223-336-033; or [email protected]).

The lithium-ion intercalation of NCHU-3 was prepared according to our previous procedures.[16] _{The cathode was fabricated by}

compressing powdered Li·NCHU-3 (85 %), black carbon (10%) and PTFE (5 %) on an aluminum disk. The pellet was then dried at 120 8C in air. The electrolyte was prepared by dissolving LiClO4in a

mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl formate (MF) (volume ratio 50:45:5) to give a 1m solution. Some properties of this electrolyte were reported.[19]

Received: November 13, 2002 [Z50544]

.

Keywords: gallium · hydrothermal synthesis · intercalations ·

microporous materials · vanadium

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