synthesis and properties of supramolecular compounds on the base of layered double hydroxides

SYNTHESIS AND PROPERTIES OF SUPRAMOLECULAR COMPOUNDS ON THE BASE OF LAYERED DOUBLE

HYDROXIDES

Isupov V.P., Tarasov K.A., Chupakhina L.E., Mitrofanova R.P., Starikova E.V.

Institute of Solid State Chemistry and Mechanochemistry SB RASKutateladze-18, Novosibirsk, 630128

Novosibirsk State University,Pirogova-2, Novosibirsk, 630090

E-mail:isupov@solid.nsk.su

General formula of layered double hydroxyde (LDH):General formula of layered double hydroxyde (LDH):

[M(II)(1-X)M(III)X(OH)2]Y+(An-Y/n)mH2O

M(II)= Mg2+, Ni2+, Co2+, Zn2+, Ca2+, etc.M(III)=Al3+, Cr3+, Fe3+, Mn3+, etc.

An- - interlayer anions

For Li+: [LiAl2(OH)6]+nAn-·mH2O

Fig. 1. Structure of LDH with anions and water molecules in the interlayer space.

Methods of LDHs synthesis:Methods of LDHs synthesis:

• Coprecipitation of LDH from basic solutions containing salts of M2+ and M3+:

(1-x)M(II) + xM(III) + 2(OH)- + Y/nAn- + mH2O =[M(II)(1-x)M(III)x(OH)2]Y+(An-

Y/n)·mH2O

• Topotaxial reactionsAnion exchange method:

[M(II)(1-x)M(III)x(OH)2]Y+(An-Y/n)·mH2O +Bm-

[M(II)(1-x)M(III)x(OH)2]Y+(Bm-Y/m)·nH2O + An-

•Large amount of wastes•Poor crystallinity of products•Restriction in the value of X in the product composition to the range 0,2-0,3

Direct intercalation LiDirect intercalation Li++ salts into the Al(OH) salts into the Al(OH)33

LinX + 2nAl(OH)3 + mH2O = [LiAl2(OH)6]nX·mH2O

Fig. 2. Scheme of intercalation of Li salts into Al(OH)3

Mechanochemical activation of mixture Mechanochemical activation of mixture of hydroxides of divalent metalsof hydroxides of divalent metals and salts of Mand salts of M3+3+

3Mg(OH)2 + AlCl36H2O = [Mg2Al(OH)6]ClnH2O + MgCl2

(for example)

4.75

2.36

7.763.92

7.69 3.87

8.70

8.704.40

1

2

3

4

5

Fig.3. Powder X-ray diffraction patterns of various samples:1- initial Mg(OH)2,2-5 - products of mechanical treatment of Mg(OH)2 with aluminium salts. Time of treatment - 3 min (2),

15 min (3,4,5). Aluminium salts- AlCl36H2O (2,3), Al(NO3)39H2O (4), Al2(SO4)318H2O (5).

0 10 20 30 40

2

Interaction of dawsonite and salts Interaction of dawsonite and salts of transition metals and Mgof transition metals and Mg2+2+

NaAl(OH)2CO3 – basic carbonate of sodium and aluminium or dawsonitedawsonite

5 10 15 20 250

8.78 A

8.55 A

7.94 A

7.55 A

5.69 A

24 h

4 h

2 h

1 h

dawsonite(cryst.) + Ni(NO3)2

Fig. 4. Interaction dawsonite with aqueous solution of Ni(NO3)2

(Ni/Al=0.5)

2

Probable scheme of interaction of dawsonite and Ni(NOProbable scheme of interaction of dawsonite and Ni(NO33))22

Proposed methods of LDHs synthesis:Proposed methods of LDHs synthesis:

Direct intercalation LiDirect intercalation Li++ salts into the Al(OH) salts into the Al(OH)33

Mechanochemical activation of mixture Mechanochemical activation of mixture of hydroxides of divalent metalsof hydroxides of divalent metals and salts of Mand salts of M3+3+

Interaction of dawsonite and salts Interaction of dawsonite and salts of transition metals and Mgof transition metals and Mg2+2+

Fig.5. X-ray diffraction pattern: 1 - Li-Al-Cl, 2 - Li-Al-Co(edta), 3 - Li-Al-Cu(edta),4 - Li-Al-Ni(edta).

X-ray diffraction pattern of supramolecular compoundsX-ray diffraction pattern of supramolecular compoundson the base of Li-Al layered double hydroxideon the base of Li-Al layered double hydroxide

Scheme supramolecular system on the base of Li-Al LDHScheme supramolecular system on the base of Li-Al LDH

Fig. 6. Sheme of Li-Al-M(edta) without water molecules (1 - N, 2 - O, 3 - M, 4 - C)

TeTermal decomposition of [LiAlrmal decomposition of [LiAl22(OH)(OH)66]]22[Medta]·mH[Medta]·mH22OO

(M=Ni(M=Ni2+2+, Cu, Cu2+2+, , ССoo2+2+))

LDH-Niedta

(4000 C)

LDH-Cuedta

(4000 C)

LDH-Coedta

(4500 C)

LDH-Coedta

(4500 C)

Electron microscopic studies (SEM and TEM) of the products formed during thermal desomposition of the intercalates LiAl2(OH)6]2[Cuedta]·4H2O and [LiAl2(OH)6]2[Coedta]·4H2O showed that the decomposition is accompanied by the formation of nano-crystal metal particles with a size from 2 to 100 nm distributed chaotically both over the volume and on the surface of the amorphous oxide matrix. In the case of thermal decomposition of [LiAl2(OH)6]2[Niedta]·4H2O, the size of the formed nano-sized nickel particles is close to 5 nm, their size disrtibution being very narrow. The mean distance between nickel particles in the

amorphous matrix is 20 nm.

ConclusionsConclusions1. New methods of LDHs synthesis can be based on topotaxial

reactions.

2. It have been shown a possibility of using the obtained LDHs as matrixes for preparation the supramolecular compounds with layered structure, containing complex anions: [M(edta)]2-

(M - Ni, Cu, Co, Zn, Pb, Mg, Mn), [Fe(edta)(OH)]2-, [M(nta)]- (M - Ni, Cu, Co).

3. It have been shown a possibility of using the obtained LDHs as matrixes for preparation the composite materials containing nanosized particles of various metals.

The investigation was supported by the Program "Scientific Research in Higher School into the Priority Directions of Science and Technology" (Grant N 3Н-118-01) and the Russian Foundation for Basic Research (Grant 02-03-32066).