CO2 Adsorption in 

Heterometallic MetalOrganic Frameworks

BY: ANTHONY CAMPANELLA

MENTORS: BEN TRUMP & CRAIG BROWN
Background

Porous materials have the potential to play a large role in future energy technologies

H2 and CH4 storage and selective adsorption of CO2 from industrial exhaust

Extremely high surface areas—~1,000 m2/g for zeolites and ~10,000 m2/g for metal-organic 

frameworks 

With porous 

material present

=

Standard gas cylinders 
Metal-Organic Frameworks (MOFs)

Composed of organic ligands coordinated to a metal center

High surface-area to mass ratios, low densities and thermal expansion indices

Tunable—thousands of combinations of metals and ligands exist, with many more to be discovered

Heterometallic MOFs contain more than one metal

Eddaoudi, M. Science 2002, 295 (5554), 469–472.
Motivation

A recent paper published in JACS asserted that certain heterometallic MOFs had:

◦ Exceptionally high CO2 uptakes, isosteric heats of adsorption (Qst) and surface areas

◦ Qst numbers for V/Mg are record breaking

Zhai, Q.-G.; Bu, X.; Mao, C.; Zhao, X.; Feng, P. Journal of the American Chemical Society 2016, 138 (8), 2524–2527.

1459 m2/g (Fe/Mg)

1347 m2/g (In/Mg)

1011 m2/g (V/Mg)
The MOFs Investigated

Synthesized in collaboration with Prof. Eric Bloch’s lab at the University of Delaware

Activated and prepared for characterization at the NCNR

N

N

O

HO OH

O

HO

O O

OH

Ligand (H4ABTC) MOF Metal Cluster MOF Unit Cell
Synthesis and Activation

In/Mg MOF Fe/Mg MOF V/Mg MOF 100 200 300 400 500

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Mass (%)

Temp (oC)

 Fe/Mg Before Activation

Thermogravimetric Analysis (TGA)

MCl3 + 2Mg(OAc)2 + 1.5H4ABTC [MMg2(OH)(ABTC)1.5(H2O)3]

Water + DMA

90 oC 2-5 Days

Water 

Removed 

(250 °C)

Solvent 

Removed 

(120 °C)

Structure 

Decomp 

(350 °C)
Gas Adsorption

Conducted on a system built in house

Surface area, pore volumes, and Qst can be determined from adsorption data

Brunauer-Emmett-Teller (BET) theory describes multilayer adsorption

CO2 isotherms at two temperatures can be used to determine Qst through the Virial Equation 

◦ ln PP = ln nn + 1

TT ∑ aaiinnii + ∑ bbiinnii

◦ QQssss = −RRTT2 δδ ln PP

δδ

= −RR ∑ aaiinnii
N2 Adsorption Isotherms for Fe/Mg MOF

0 100 200 300 400 500 600 700 800

0

50

100

150

200

250

300

350

400

450

500

550

Uptake (STP) cc/g

Pressure (Torr)

77K

Fe/Mg MOF N2 Adsorption

BET Surface Area: 1246 m2/g

Pore Volume: 0.55 cc/g

Zhai, Q.-G.; Bu, X.; Mao, C.; Zhao, X.; Feng, P. Journal of the American Chemical Society 2016, 138 (8), 2524–2527.

Published Isotherm Experimental Isotherm

BET Surface Area: 1459 m2/g

Pore Volume: 0.72 cc/g BET Surface Area: 1459 m2/g

Pore Volume: 0.72 cc/g
N2 Adsorption Isotherms for V/Mg MOF

BET Surface Area: 1019 m2/g

Pore Volume: 0.429 cc/g

BET Surface Area: 1011 m2/g

Pore Volume: 0.50 cc/g

Zhai, Q.-G.; Bu, X.; Mao, C.; Zhao, X.; Feng, P. Journal of the American Chemical Society 2016, 138 (8), 2524–2527.

0 100 200 300 400 500 600 700 800

0

50

100

150

200

250

300

350

400

Uptake (STP) cc/g

Pressure (Torr)

V/Mg MOF N2 Adsorption

77 K

Published Isotherm Experimental Isotherm
Comparison to the Full Data

Zhai, Q.-G.; Bu, X.; Mao, C.; Zhao, X.; Feng, P. Journal of the American Chemical Society 2016, 138 (8), 2524–2527.

77 K

0 100 200 300 400 500 600 700 800 900

0

100

200

300

400

500

Uptake (STP) cc/g

Pressure (Torr)

 Fe/Mg

 V/Mg
CO2 Adsorption Isotherms for Fe/Mg

0 100 200 300 400 500 600 700 800 900 1000

0

20

40

60

80

100

120

140

160

180

200

220

Uptake (STP)cc/g

Pressure (Torr)

273K

297K

Fe/Mg MOF CO2 Adsorption

Zhai, Q.-G.; Bu, X.; Mao, C.; Zhao, X.; Feng, P. Journal of the American Chemical Society 2016, 138 (8), 2524–2527.

Published Isotherm Experimental Isotherm
CO2 Adsorption Isotherms for V/Mg

Zhai, Q.-G.; Bu, X.; Mao, C.; Zhao, X.; Feng, P. Journal of the American Chemical Society 2016, 138 (8), 2524–2527.

0 100 200 300 400 500 600 700 800 900 1000

0

20

40

60

80

100

120

140

160

180

Uptake (STP) cc/g

Pressure (Torr)

273K

297K

V/Mg MOF CO2 Adsorption

Published Isotherm Experimental Isotherm
Heats of Adsorption

V/Mg

Fe/Mg

Zhai, Q.-G.; Bu, X.; Mao, C.; Zhao, X.; Feng, P. Journal of the American Chemical Society 2016, 138 (8), 2524–2527.

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

0

10

20

30

40

50

60

70

80

90

100

 Fe/Mg

 V/Mg

Qst (KJ/mol)

CO2 Uptake (mmol/g)
Diffraction

Waves of angstrom scale diffract off of a crystal lattice and produce a distinct pattern

This diffraction is described in Bragg’s Law:

◦ 2dd sin θθ = nnnn

X-rays and thermal neutrons have the correct wavelength ranges

◦ X-rays: 1 Å - 2 Å

◦ Neutrons: 1.2 Å - 2.08 Å
Neutron Diffraction

Why neutrons?

◦ With X-Ray diffraction there is difficulty seeing lighter elements when contrasted by metals

◦ Neutrons can detect these lighter elements in conjunction with the metals

High-Resolution Powder Diffractometer (BT-1) was used to confirm structure of synthesized 

MOFs

MOFs were dosed with stoichiometric amounts of CO2 during diffraction experiment
BT-1 Powder sample in vanadium can
CCR attached to CO2 Sample in aluminum can—ready for the beam line for gas dosing
Diffraction Patterns of Fe/Mg MOF

0 5 10 15 20 25 30 35 40

0

500

1000

1500

2000

2500

3000

3500

4000

Intensity (Counts)

2θ (o)

2 Eq Dose

1 Eq Dose

2/3 Eq Dose

1/3 Eq Dose

No CO2
Diffraction Patterns of In/Mg MOF

0 5 10 15 20 25 30 35 40

0

1000

2000

3000

4000

5000

6000

7000

Intensity (Counts)

2θ (

o

)

 1 Eq Dose

 2/3 Eq Dose

 1/3 Eq Dose

 No CO2
Bare Structure Fit of Fe/Mg MOF

0 10 20 30 40 50 60 70 80 90 100

0

2000

4000

6000

8000

10000

12000

14000

16000

Intensity (Counts)

2θ (o)
Preliminary Refined Structure with CO2

0 20 40 60 80 100 120 140

0

2000

4000

6000

8000

10000

12000

14000

16000

Intensity (Counts)

2θ (o)

2.1 Å

50/50 Occupancy 

of Fe/Mg

1/3 Occupancy of 

CO2

Multiple Orientations of 

Water
CO2

H2O
Conclusions and Future Work

Data derived from adsorption isotherms fall in the expected range for open metal site MOFs

Structure is correct—Right materials are produced

CO2 binds to open metal site, displacing water molecule

Further studies into the effects of water on adsorption

Inductively Coupled Plasma-Optical Emission Spectroscopy to determine metallic ratios

More structural and isotherm data
Acknowledgements

Mentors: Ben Trump & Craig Brown

Prof. Eric Bloch, Eric Gosselin

Dr. Taner Yildirim

Drs. Joseph Dura, Julie Borchers, and Brandi Toliver

Center for High Resolution Neutron Scattering

All the NCNR SURFers