Festkörper-NMR-UntersuchungenFestkörper-NMR-Untersuchungender Struktur und Dynamik in anorganischen Materialiender Struktur und Dynamik in anorganischen Materialien

Dieter FreudeAbteilung Grenzflächenphysik, Universität Leipzig, www.grenzflaechenphysik.de

Vortrag am 10. Februar 2004 an der Universität Karlsruhe, Forschergruppe 338, Professor Hans Buggisch

O1O2

O4O3

III

IIII’

I’

I

Faujasite

O1O2

O4O3

III

IIII’

I’

I

B0

2

1

inner

outer

Current ContentsCurrent Contents®®

The Current Contents© (Physical, Chemical and Earth Sciences) referred in the last years to more than 200 000 publications, among them 35 000 spectroscopic studies, about 9 000 NMR studies, among them to 2 000 studies of solids.

From all NMR studies refer ca. 35% to 1H, ca. 25 to 13C, ca. 8 to 31P, ca. 8 to 15N, ca. 4 to 29Si and ca. 2 to 19F as I  ½ nuclei.

Ca. 3% refer to 27Al and ca. 1% to 11B, 1% to 7Li, 1% to 23Na, 1% to 51V (half-integer spin nuclei I >½). Ca. 4% refer to 2H, ca. 0.5% to 14N and 0,5% to 6Li (integer spin nuclei with I = 1).

0

1000

2000

3000

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6000

7000

8000

9000

10000

NMR IR

Raman M

SEPR

DK

1994

1995

1996

1997

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1999

2000

2001

Vergleich im Jahre 2000 zwischenPhysical, Chemical & Earth Sciences

und Life Sciences

0100020003000400050006000700080009000

10000

NMR IR

Raman M

SEPR

X-ray s

pectr

osco

py DK

X-ray s

tructu

re

Phys

Life

Harry Pfeifer's NMR-Experiment 1951 in LeipzigHarry Pfeifer's NMR-Experiment 1951 in Leipzig

H. Pfeifer: Über den Pendelrückkoppelempfänger und die Beobachtungen von magnetischen Kernresonanzen, Diplomarbeit, Universität Leipzig, 1952

Laser-Einsatz:Laser-Einsatz:

Laser supported high-temperature MAS NMRLaser supported high-temperature MAS NMR

MAS Rotor 7 mm

CO2 Laser

Cryo Magnet

B0

Stop-and-goStop-and-go A laser beam makes it possible to switch from room temperature, at which chemical reactions in zeolites are commonly too slow to be measured, to temperatures up to 800 K, at which the reaction takes place within a few seconds.

Laser Power

stop stop t

Temperaturego go

NMR of Reversible Reactions

1H (t)

0 t t1

NMR of Irreversible Reactions

13C () 13C (2) (+t t1)

t1++

t

t

0 0 treactiontreaction

Irreversible reactions: The stop-and-go technique utilizes the heating rate of the laser-supported probe to expose the sample to short periods at high temperatures and splits the measuring time in consecutive stop and go periods. During the go periods the time development of irreversible reactions can be monitored at high temperatures by equidistant 1H MAS NMR signals. The reaction state after each go period is recorded by a 13C MAS NMR spectrum at room temperature during the stop period.

Reversible reactions: FID accumulation and phase cycling can be realized by multiple repetition of the heating-cooling cycle. The recording of one complete heating and cooling cycle by means of several FIDs equidistant in time is denoted herein as one FID set.

Hochfeld-Festkörper-NMR:Hochfeld-Festkörper-NMR:

Festkörper-NMR-Spektroskopie im hohen Magnetfeld, Festkörper-NMR-Spektroskopie im hohen Magnetfeld, einschließlich DOR und MQMAS für Quadrupolkerne wie einschließlich DOR und MQMAS für Quadrupolkerne wie 1717OO

The Bruker Avance 750 spectrometer in Leipzig, painting by Dr. Taro Ito

Application

of m

ode

rn N

MR

-tec

hn

iques to high reso lu tion spectroscopy of quadrupole nuclei

3QMAS pulse program

DOR rotor

B0

2

1

inner

outer

p

5 4 3 2 1 0 1 2 3 4 5

t1 t t2

composite pulse FAM2

two-pulse with x-filter

Was ist Ziel neuer Festkörper-NMR-TechnikenWas ist Ziel neuer Festkörper-NMR-Technikenzur Untersuchung von Quadrupolkernen?zur Untersuchung von Quadrupolkernen?

Was ist Ziel neuer Festkörper-NMR-TechnikenWas ist Ziel neuer Festkörper-NMR-Technikenzur Untersuchung von Quadrupolkernen?zur Untersuchung von Quadrupolkernen?

Verbesserung der Auflösung zur genaueren Bestimmung der chemischen Verschiebung von Signalen

Verbesserung der Auflösung zur genaueren Bestimmung von Quadrupolparametern

Verbesserung der Nachweisempfindlichkeit

Theoretische Linienform des Zentralübergangs mit Anisotropiefaktor  = 0,2 und geringer Gaußverbreiterung für das ohne Probenrotation aufgenommene statische Spektrum, das MAS-Spektrum und das MQMAS NMR-Spektrum.

DOR-Spektrum sieht wie MQMAS aus, hat aber meist viele Seitenbänder.

Einquanten- und MultiquantenübergängeEinquanten- und MultiquantenübergängeEinquanten- und MultiquantenübergängeEinquanten- und Multiquantenübergänge

m

5/2

1/2 3/2

Der Aluminiumkern hat den Spin I = 5/2. Entsprechend ergeben sich sechs Energieniveaus im starken äußeren Magnetfeld.

Satelliten, Zentralübergang, Verbreit. 2. OrdnungSatelliten, Zentralübergang, Verbreit. 2. OrdnungSatelliten, Zentralübergang, Verbreit. 2. OrdnungSatelliten, Zentralübergang, Verbreit. 2. Ordnung

L

Q

3 2 1 0 -1 -2 -3 3 2 1 0 -1 -2 -3

= 0 = 1

I = 3/2

I = 5/2

I = 7/2

16

9 16

9 32

9 1 0 0 5

6 14

9 4

21

L

Q2

L161

3

4I I

= 0

= 0.5

= 1

MAS static

MAS, Verbr. 2. Ordnung, symmetrische Übergänge MAS, Verbr. 2. Ordnung, symmetrische Übergänge MAS, Verbr. 2. Ordnung, symmetrische Übergänge MAS, Verbr. 2. Ordnung, symmetrische Übergänge

p p p p

pI I p

pd d d

I I p

/ , /

, , ,cos cos

cos cos ,

2 2

2

2

20 0

42 0

4 24 0

4

2 4 2

3

901

3

4

1296018 360 2 70 4

36 1 17 109

2835 30 3

iso Q aniso Q

Q2

L

Q2

L

2

1

2

1

y

z

Z

J

Iy

2 sin1

Iz (1 +2 cos1)

B0

double rotation: 2 = 54,74°

1 = 30,56°

Iy/Ix tuned

to J Z

/ ppm 0 20 40 60

* * * * *

*

Na,K-LSX17O MAS17O DOR

11,7 T 17,6 T

p

5 4 3 2 1 0 1 2 3 4 5

t1 t t2

two-pulse with x-filter

MQMAS pulse sequences:

Selection of the desired coherence transfer path by the phase cycling.

H217O

423

1

04080 /ppm

iso= 53.6 ppm

iso= 49.4 ppm

iso= 45.9 ppm

iso= 41.1 ppm

204060 2/ppm

40

60

20

60 40 202/ ppm

iso/ ppm

Na-LSX 3QMAS

MQMASMQMAS andand DORDOR

wide-bore probe νouter 1.8 kHz, νinner 7.6 kHz, narrow-bore probe νouter 1.5 kHz, νinner 7.5 kHz,

Double rotationDouble rotation

NMR-Diffusometrie (Kärger):NMR-Diffusometrie (Kärger):

PFG NMR-MesstechnikPFG NMR-Messtechnik

Festkörper-Technik für Diffusometrie:Festkörper-Technik für Diffusometrie:

SFG NMR-Messtechnik SFG NMR-Messtechnik für Temperaturen bis 700 Kfür Temperaturen bis 700 K

hf-pulses t

/2

gradient pulses for comparison

t

magnetization in the homogeneous field for comparison

t

free induction echo

fringe field gradient

t

magnetization in the fringe field

t

free induction echo

-0.0030 -0.0025 -0.0020 -0.0015 -0.0010 -0.0005 0.0000

-5

-4

-3

-2

-1

0

ln

-2/32D3 /m-2sResult:

The magnetic field gradient in the fringe field of the BRUKER wide-bore 17.6 T magnet amounts 40.56 T m-1 for a proton resonance frequency of 303 MHz.

11H MAS NMR of porous materialsH MAS NMR of porous materials

0 2 4 6 7 5 ppm 3 1

Bridging OH groups in small channels and cages of zeolites

SiOHAl

Disturbed bridging OH groups in zeolite H-ZSM-5 and H-Beta

SiOH

Bridging OH groups in large channels and cages of zeolites SiOHAl

Cation OH groups located in sodalite cages of zeolite Y and in channels of ZSM-5 involved in hydrogen bonds

CaOH, AlOH, LaOH OH groups bonded to extra-framework aluminium species located in cavities or channels involved in hydrogen bonds

AlOH Silanol group at the externel surface or at lattice defects

SiOH

Metal or cation OH groups in large cavities or at the outer surface of particles MeOH

11H MAS NMR spectraH MAS NMR spectra

modul30 I/D calc. temp. 550 °Cdehydrated

420246 8 10 / ppm

modul30 II/D calc. temp. 900 °Cdehydrated

20 468 10 / ppm

4

4.2 ppm 2.9 ppm2.9 ppm

2.2 ppm

1.7 ppm

2.2 ppm1.7 ppm2.9 ppm2.9 ppm

with dephasing

without dephasing

difference spectrum

2

with and without dipolar dephasing by 27Al high power irradiation and difference spectra. Non- framework aluminium (EF), OH group of the framework (F). Spectra shows SiOH groups at framework defects, at the surface, SiOHAl-bridging hydroxyl groups, Al – OH group.

2929Si MAS NMRSi MAS NMR

ppm

Si(1 Zn)

Si(2 Zn) zincosilicate-type zeolites

VP-7, VPI-9 Q4

alkali and alkaline earth silicates

Q0

Q2

Q1

Q4

Si(1 Al)

Si(0 Al)

Si(2 Al)

Si(3 Al)

Si(4 Al)

Si(3Si, 1OH)

aluminosilicate-type zeolites

Q3

Q4

Q3

29Si MAS NMR-Spektrum von Silicalit 1, das aus einem SiO2-Gerüst mit 24 unterschiedlichen Si-Positionen pro

Einheitszelle besteht (Fyfe 1987)

2727Al MAS NMRAl MAS NMR

0 10 20 30 40 50 60 70 80 90 100 10 110 120 ppm

aluminates

aluminosilicates

aluminoborates

aluminophosphates

aluminates

aluminosilicates

aluminoborates

aluminophosphates

aluminates

aluminosilicates

aluminoborates

aluminophosphates

aluminosilicates

3-fo

ld

coor

d.

4-fo

ld

coor

dina

ted

5-fo

ld

coor

dina

ted

6-fo

ld

coor

dina

ted

20

Hydrothermally treated zeolites ZSM-5Hydrothermally treated zeolites ZSM-5

L = 195 MHz

Rot = 15 kHz

/ ppm

60 40 20 0 20 40 60 80 100

L = 130 MHz

Rot = 10 kHz

four-fold coordinated

five-fold coordinated

six-fold coordinated

AlPOAlPO44-14, -14, 2727Al 3Q MAS spectrumAl 3Q MAS spectrum

L = 195 MHz

Rot = 30 kHz ppm

45 40 35 30 25 20 15 10 5 0 ppm

50

40

30

20

10

0

CS,iso=42.9 ppm

Cqcc=1.74 MHz = 0.63 [6]

CS,iso=27.1 ppm

Cqcc=5.58 MHz = 0.97 [6]

CS,iso= 1.3 ppm

Cqcc=2.57 MHz = 0.7 [6]

CS,iso=43.5 ppm

Cqcc=4.08 MHz = 0.82 [6]

ppm

45 40 35 30 25 20 15 10 5 0 ppm

50

40

30

20

10

0

ppm

45 40 35 30 25 20 15 10 5 0 ppm

50

40

30

20

10

0

CS,iso=42.9 ppm

Cqcc=1.74 MHz = 0.63 [6]

CS,iso=27.1 ppm

Cqcc=5.58 MHz = 0.97 [6]

CS,iso= 1.3 ppm

Cqcc=2.57 MHz = 0.7 [6]

CS,iso=43.5 ppm

Cqcc=4.08 MHz = 0.82 [6]

1717 O NMR, hydrothermal O NMR, hydrothermal enrichmentenrichment

N2

H217O

zeolite

reactor

heater

N2

condenser

• H217O (25 - 43% enriched),

vapor pressure of 2.4 kPa in a nitrogen stream

• zeolite embedded in quartz glass particles

• temperature between 150 °C and 250 °C

• duration of some hours, water is recycled

ice

Question: Question: EExists a correlation between xists a correlation between 1717OO chemical shift chemical shift and T-O-T bond angleand T-O-T bond angle ??

17O DOR NMR for the oxygen sites of hydrated Na-A ( ) and Na,K-LSX ( ).

(17O) /ppm = 214 + 136 (17O) /ppm = 0.65/° + 134

correlation coefficients:0.924 and 0.91

Grandinetti et. al. [2] and Bull et. al. [3], [4] claimed that a monotone correlation between Si-O-Si bond angle and 17O chemical shift does not exist.

In 29Si NMR a relation exists between the isotropical value of the chemical shift and the mean value of the Si-O-T angles (T=Si, Al), cf. Radeglia and Engelhardt [1]:

  (29Si) = 223.9 7.2 + 5m .

= cos/(cos  1) is the s-character of the oxygen hybrid orbitals, and m the coordination number of Si atoms to Al atoms, commonly Q4(m Al).

17O DAS NMR studies of the SiO2 polymorph coesite by Grandinetti et. al. [2] yielded the correlations:

2)180(1cos

cos2)180( qccqccqcc

CCC

cos1

[1] Chem. Phys. Lett. 114 (1985) 28[2] J. Phys. Chem. 99 (1995) 12341

[3] J. Am. Chem. Soc. 120 (1998) 3510[4] J. Am. Chem. Soc. 122 (2000) 4948

Mobility in the Brønsted CenterMobility in the Brønsted Center

Proton mobility of bridging hydroxyl groups in zeolites H-Y and H-ZSM-5 was monitored in the temperature range from 160 to 790 K. The full width at half maximum of the 1H MAS NMR spectrum narrows by a factor of 24 for zeolite H-ZSM-5 and a factor of 55 for zeolite 85 H-Y. For the latter an activation energy of 78 kJ mol has been determined.

Si

Si

Al

Si

Si

O1

O4

O2

O3

Si

Si

Al

Si

Si

O1

O4

O2

O3

zeolite 85 H-Y

Ea = 78 kJ/mol

zeolite H-ZSM-5

Ea = 18 kJ/mol

MAS

rot rot

M c

c

c

c

22 2

2

1 1 2

The values of the activation energy for the proton mobility around an aluminum atom are useful for the evaluation of quantum chemical models.

Proton transfer between Brønsted Proton transfer between Brønsted sites and benzene molecules in sites and benzene molecules in

zeolites H-Yzeolites H-YIn situ 1H MAS NMR spectro-scopy of the proton transfer between bridging hydroxyl groups and benzene molecu-les yields temperature depen-dent exchange rates over more than five orders of magnitude.

H-D exchange and NOESY MAS NMR experiments were performed by both conventional and laser heating up to 600 K.

Exchange rate as a dynamic measure of Brønsted acidityExchange rate as a dynamic measure of Brønsted acidity

Arrhenius plot of the H-D and H-H exchange rates for benzene molecules in the zeolites 85 H-Y and 92 H-Y. The values which are marked by blue or red were measured by laser heating or conventional heating, respectively.

The variation of the Si/Al ratio in the zeolite H-Y causes a change of the deprotonation energy and can explain the differences of the exchange rate of one order of magnitude in the temperature region of 350600 K. However, our experimental results are not sufficient to exclude that a variation of the pre-exponential factor caused by steric effects like the existence of non-framework aluminium species is the origin of the different rates of the proton transfer.

10

10

10

10

1.5 2.71.9 2.3

92 H-Y

85 H-Y

1000

T/K

k /min

Herzlichen Dank für die Beiträge von

Horst Ernst Thomas Loeser

Johanna KanellopoulosJörg KärgerBernd Knorr

Dieter Michel Lutz Moschkowitz

Ulf PingelDagmar Prager

Daniel Prochnow

Deutsche ForschungsgemeinschaftMax-Buchner-Stiftung