Metal-Organic Framework Materials for Energy Applications

• U.S. Dept. of Energy• AFOSR• Northwestern NSEC • DTRA

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Notre Dame, November, 2010

Acknowledgments

• Avi Shultz

• Dr. Andy Nelson

• Prof. SonBinh Nguyen

• Prof. Randall Snurr

Acknowledgments

• Research Prof. Omar Farha

• Hydrogen storage• Chemical catalysis• Carbon dioxide

capture and storage • Gas separations• Light harvesting and

energy conversion

Metal-Organic Framework Materials for Energy Applications

• Solvothermal synthesis simple, scalable materials assembly

• Broad channel and pore size tunability

• Complete uniformity of channels

• Amenable to experimental structural characterization

Why Metal-Organic Frameworks?

• Amenable to detailed explanative and predictive computational characterization

• Enormous internal surface areas: up to 5,200 m2/g(e.g. Matzger)

Materials Challenges

Purification

Retaining porosity

Controlling catenation

b) Catenated versus non-catenated:

a) Paddlewheel from cubic

Problem: MOFs Are Often Obtained as Solid-state Mixtures

Acc. Chem, Res. 2010, 43, 1053-1176

NN

O O NNZn

R R

O

HO

OH

O

+Zn(NO3)2 6H2O

70 oC, 5 days

+ unknown+ Zn(NO3)2

DMF/70 °C+

Solution: Density based separation using high-density solvents

NN

O O NNZn

R R

O

HO

OH

O

+Zn(NO3)2 6H2O

70 oC, 5 days

+ unknown

Process of separation

yellow

white

+ Zn(NO3)2

DMF/70 °C+

5 10 15 20 25 30 35

Two Theta (2θ)

θ

5 10 15 20 25 30 35

5 10 15 20 25 30 35

A

B

C

*

5 10 15 20 25 30 35

Two Theta (2θ)

θ

5 10 15 20 25 30 35

5 10 15 20 25 30 35

A

B

C

*

Solution: Density based separation

Differences in porosity and surface area

0.10.20.30.40.50.60.70.80.9

1

25 125 225 325 425 525Temperature (°C)

Wei

ght F

ract

ion

0102030405060708090

100

0.00 0.20 0.40 0.60 0.80 1.00

Pressure (atm)

CO

2 Vol

ume

(cc/

g)

ads of 12des of 12ads of 11des of 11

Vs.

Materials Challenges

Purity

Retaining porosity

Controlling catenation

Case Study: Preventing Collapse of Cubic “TClPDl” MOF

BET Surface Area:

Conventional evacuation 22 m2/g completely “collapsed”

Supercritical CO2 evacuation 490 m2/g highly porous

NN

O

O

O

O

Cl

Cl

O

OH

HO

O

Cl

Cl

Nitrogen adsorption isotherms

490 m2/g

22 m2/g

Other Examples with Supercritical CO2…

<50 m2/g (simple solvent evac.)

2,100 m2/g (CHCl3 exch.)

3,200 m2/g (scD)

1,900 m2/g (scD)

470 m2/g (CHCl3 exch.)

Materials Challenges

Purity

Retaining porosity

Controlling catenation

catenated non-catenated

Catentated versus non-catenated MOFs• nearly all “paddle-wheel” MOFs are catenated• but, for most applications, we desire

non-catentated MOFS

Examples of Catenated Paddlewheel MOFs

• Zn2(dicarboxylate)2(dipyridyl)

1 2 3

4 5 6

7 8 9

Ma, et al. Inorg. Chem., 2005, 44, 4912-4914

C

B

E F

D

A

C

B

E F

D

A

Zn2 =

Control over Catenation…

Acc. Chem, Res. 2010, 43, 1053-1176

Mixed ResultsA)

B)

Redesigning the Tetratopic Strut

Control over Catenation

Metal-Organic Framework Materials for Energy Applications

• Hydrogen storage • Catalysis• Chemical sensing• Gas separations• Light harvesting…

J. Am. Chem. Soc., 2007, 129, 9604-9605.Langmuir, 2009; Inorg. Chem. 2008

Hydrogen storage. DOE-mandated goal:• 10 wt. percent• 100 bar or less• -30oC (243K)

Metal-Organic Framework Materials for Energy Applications

Hydrogen storage. DOE-mandated goal:• 10 wt. percent 5.5 %• 100 bar or less• -30oC (243K)

Metal-Organic Framework Materials for Energy Applications

Goals New Metal-Organic Frameworks Featuring:

• High surface areas• Highly accessible H2

binding sites • Extraordinary heats of

adsorption• High H2 storage

capacity at ambient temperature

Goals New Metal-Organic Frameworks Featuring:

• High surface areas• Highly accessible H2

binding sites • Extraordinary heats of

adsorption• High H2 storage

capacity at ambient temperature

Materials Design via Computational Modeling

R. Q. Snurr and co-workers, Northwestern.

Literature: High Surface Area MOFs

R. Q. Snurr and co-workers, Northwestern.

Why this topology: (a) high stability under ambient conditions (b) unsaturated coordination sites (Cu(II) sites)(c) impossibility of forming interpenetrated multi-network

structures.

Cu-salt

Target Coordination and Topology

cf. M. Schroder, et al. and H-C. Zhou, et al.

Why this topology: (a) high stability under ambient conditions (b) unsaturated coordination sites (Cu(II) sites)(c) impossibility of forming interpenetrated multi-network

structures. cf. M. Schroder, et al. and H-C. Zhou, et al.

Target Coordination and Topology

New Hexatopic Strut 3,24 Net Expected

Structure Prediction

Combine new strut with Cu-paddlewheels in Fm-3m space group

R. Q. Snurr, et al.

Predicted Surface Area of NU-100

Simulated Structure → Simulated N2 isotherm → BET Model

Applicability of the BET method to MOFs: Y. S. Bae, O. Yazaydin, R. Q. Snurr, “Evaluation of the BET Method for Determining Surface Areas for MOFs and Zeolites that Contain Ultramicropores,” Langmuir 2010, 26, 5475-5483.

Predicted Surface Area of NU-100

Simulated Structure → Simulated N2 isotherm → BET Model

Applicability of the BET method to MOFs: K. S. Walton, R. Q. Snurr, “Applicability of the BET Method for Determining Surface Areas of Microporous Metal-Organic Frameworks,” J.Am.Chem.Soc. 2007, 129, 8552-8556.

What we find: NU-100

≈14 Å

≈28 Å

≈15 Å

cubaoctahedral

truncated tetrahedral

truncated octahedron

What we find: NU-100

What we find: NU-100

MOF Activation: Can We Use This New Material?

• Heating at 100°C under vacuum Failed• Solvent exchange, then room temperature

evacuation Failed-ethanol-acetone-chloroform

• Modified supercritical drying success

Supercritical CO2 ActivationConventional and Solvent Exchange Activation

Predicted Surface Area of NU-100

Simulated Structure → Simulated N2 isotherm → BET Model

Experimental BET Surface Area → 6,200 m2/g

One gram of NU-100 has the same surface area as a soccer field

One pound of NU-100 has a surface area of one square mile

1 mile2

You are here

NU-100. State-of-the-Art for MOF-based H2 Storage

42

Hydrogen uptake at 77 K and 70 bar:99.5 mg / g excess (56 bar)

164 mg / g total14.3 wt% total

45 g/L total

0

50

100

150

200

0 20 40 60Pressure (bar)

H 2 u

ptak

e (m

g/g)

NU-100 expt.(excess)NU-100 expt.(total)

Farha, et al., Nature Chemistry, 2010.

Farha, et al., Nature Chemistry, 2010.

NU-100. Ineffective at ambient temperature: Binding is too

weak…

0

50

100

150

200

0.00 0.20 0.40 0.60 0.80 1.00

Pressure (atm)

Volu

me

of H

2 (cc

/g)

77K ads77K des87K ads87K des

0 5 10 150

1

2

3

4

5

6

q st (k

J/m

ol)

N (mg/g)

Goal: Enhance H2 uptake via frame-work reduction and cation doping

• Enhanced London dispersion interactions due to enhanced strut polarizability?

• Adsorption of polarizable molecules due to electric field enhancement?

• Enhanced molecular adsorption due to charge/quadrupole interactions?

The major technical and scientific challenge in this area is to increase the heat of adsorption of H2 to ca. 15-25 kJ/mol (to enable high loading at ambient temperature)

S. Han and W. A. Goddard III J. Am. Chem. Soc., 2007, 129, 8422–8423

(Mulfort, et al. Inorg. Chem. 2005)

A Computational Example: >5 wt. % at 300K!

Framework reduction and cation doping

Exploit organic struts within frameworks to introduce charge: enhance H2 binding and uptake

Chemically reduce struts

induced dipole – induced dipole(strut) – (H2)

e- ----

Charge compensating cations

charge – quadrupole(cation) – (H2)

a reducible-framework material

(One of two identical networks shown)

Framework Reduction and Cation Doping

Observing Framework Reduction

Solid state color changes mimic solutionZn2(NDC)2(diPyNI)

+ Li(NAP)Zn2(NDC)2(diPyPI-Cl4)

+ CoCp2

3400 3420 3440 3460 3480 3500

reduced with Li(NAP)reduced with CoCp2

EPR: Reduced MOF

inte

nsity

field (G)

Solid state EPR verifies presence of radicals

0.0 0.2 0.4 0.6 0.8 1.00

100

200

300

400

500

600

volu

me

adso

rbed

(cm

3 /m

g)

P / Po

11- Li+

•Zn2(NDC)2(diPyNI) is reduced upon exposure to Li0 in DMF

•N2 adsorption displays striking hysteresis w/5% lithium doping

•Interpretation: nitrogen loading dependent conversion between interwoven and interpenetratedforms of the MOF structure

Consequences of Framework Reduction…

Hydrogen Adsorption

0.0 0.2 0.4 0.6 0.8 1.00.0

0.4

0.8

1.2

1.6

P (atm)

H2 wt%

no Li+

with Li+

+ Li0Li+-

0.0 0.2 0.4 0.6 0.8 1.00.0

0.4

0.8

1.2

1.6

P (atm)

H2 wt%

no Li+

with Li+

+ Li0Li+-

•Zn2(NDC)2(diPyNI) is reduced upon exposure to Li0 in DMF

•H2 uptake is nearly doubled w/5% doping

Consequences of Framework Reduction…

Hydrogen Adsorption

0.0 0.2 0.4 0.6 0.8 1.00.0

0.4

0.8

1.2

1.6

P (atm)

H2 wt%

no Li+

with Li+

+ Li0Li+-

0.0 0.2 0.4 0.6 0.8 1.00.0

0.4

0.8

1.2

1.6

P (atm)

H2 wt%

no Li+

with Li+

+ Li0Li+-

•Zn2(NDC)2(diPyNI) is reduced upon exposure to Li0 in DMF

•H2 uptake is nearly doubled w/5% doping 48 H2 molecules per Li+ !

Consequences of Framework Reduction…

Hydrogen Adsorption

0.0 0.2 0.4 0.6 0.8 1.00.0

0.4

0.8

1.2

1.6

P (atm)

H2 wt%

no Li+

with Li+

+ Li0Li+-

0.0 0.2 0.4 0.6 0.8 1.00.0

0.4

0.8

1.2

1.6

P (atm)

H2 wt%

no Li+

with Li+

+ Li0Li+-

•Zn2(NDC)2(diPyNI) is reduced upon exposure to Li0 in DMF

•H2 uptake is nearly doubled w/5% doping 48 H2 molecules per Li+ !•Heat of adsorption only very slightly increases

Consequences of Framework Reduction…

0 2 4 6 8 10 12 140

1

2

3

4

5

6

7

8

Ha

ds, k

J / m

ol

N, mg / g

1 1-Li+

Goal: Enhance H2 uptake via frame-work reduction and cation doping

• Enhanced London dispersion interactions due to enhanced strut polarizability?

• Adsorption of polarizable molecules due to electric field enhancement?

• Enhanced molecular adsorption due to charge/quadrupole interactions?

• Enhanced adsorption due to ion-induced displacement of catenated frameworks

Dalach, Frost, Snurr, Ellis, J. Phys. Chem. C 2008, 112,9278-9284.

Problem:Ions are sited around catenated paddlewheel nodes desired specificcation/H2 interactions are precluded

Acknowledgments