transcript
- Slide 1
- Motivation: CO 2 capture System: Metal-Organic Frameworks Data:
Unusual blue shift of adsorbed CO 2 3 mode Room-temperature
sidebands Low-temperature bands reveal 2 nd configuration
Vibrational Shift of Adsorbed CO 2 within a Metal-Organic Framework
Outline
- Slide 2
- Motivation Carbon capture Separate carbon dioxide from exhaust
gases Emissions reduction accompanying switch to clean energy
sources Natural gas purification Separate CO 2 from methane (CH 4 )
Improve energy density of fuel, decrease pipe corrosion Current CO
2 separation methods are costly Harmful materials High energy costs
for regeneration A better way?
http://www.nma.org/ccs/carboncapture.as p
- Slide 3
- Metal-Organic Frameworks Large voids, voids of ~ 10 20 for
molecular storage and separation Complex unit cell makes
computation modeling challenging Significant van der Waals
interactions Metal ions linked by organic chains Very low density
Crystalline and tunable Vast number of possible structures
- Slide 4
- Honeycomb structure Metal-oxide clusters linked by Benzene
rings MOF-74 H. Wu et al. J. Phys. Chem. Lett., 1(13):19461951,
2010. Diffraction indicates CO 2 is nearly linear 2+ Unsaturated
metal ion acts as primary binding site for CO 2 2.4
- Slide 5
- MOF-74 Isostructural Series
http://legacy.owensboro.kctcs.edu/gcaplan/bio/Notes/BIO%20Notes%20C%20intro%20chem.htm
Same structure, different metal Mg-MOF-74, Mn-MOF-74,
Fe-MOF-74,Co-MOF-74, Zn-MOF-74
- Slide 6
- Slide 7
- MOF-74 Selective Binding Binding energy in Mg-MOF-74 ~ 40 - 50
kJ/mol Binding energy in other MOF-74 at least 7 kJ/mol less
Difference is likely due to direct electrostatic interaction via
shorter Mg O bond Binding energy for CH 4 in MOF-74 ~ 20 kJ/mol
Difference between CO 2 and CH 4 mainly attributed to CO 2
quadrupole moment Caskey et al. J. Am. Chem. Soc., 130,10870,
(2008). H. Wu et al. J. Am. Chem. Soc., 131, 4995 (2009). Park et
al. Phys. Chem. Lett. 3, 826 (2012). Yao et al. Phys. Rev. B. 85,
64302 (2012).
- Slide 8
- Diffuse Reflectance Spectroscopy Light bounces around within
powder sample Very long path length enhances absorption signal
- Slide 9
- Diffuse Reflectance Spectroscopy: Cryostat Assembly Rev. Sci.
Instr. 77, 093110 (2006)
- Slide 10
- 3 mode of adsorbed CO 2
- Slide 11
- Vibration of adsorbed H 2
- Slide 12
- 3 mode of adsorbed CO 2
- Slide 13
- Side Bands: Translational/Librational 000 001 010 011 C 13
- Slide 14
- Librational Motion
- Slide 15
- MOF-74 H. Wu et al. J. Phys. Chem. Lett., 1(13):19461951, 2010.
2+
- Slide 16
- Temperature Dependence E B = 0.7 0.1 kJ/mol New band emerges
below 150 K Degeneracy ratio of ~ 2 Room temperature peaks too
broad to resolve
- Slide 17
- vdW-DF2 Theory Calculations Y. Yao et al. Phys. Rev. B, 85,
064302 ( 2012). Predicts sites 2.96 and 3.09 away from metal with
0.8 kJ/mol energy difference
- Slide 18
- Combination modes compared to Hitran Data 3 000 001 3 + Fermi
resonance 000 101 and 000 021 3 + 2 x Fermi resonance 000 201, 041,
121
- Slide 19
- Conclusion CO 2 in MOF-74 Mg version 3 mode unique in showing
blue shift All other modes show red shift Evidence for CO 2
librational/translational motion Evidence for a 2 nd nearly
degenerate adsorbed CO 2 configuration
- Slide 20
- Michael Friedman Jordan Gotdank Jesse Hopkins Brian Burkholder
Ben Thompson Chris Pierce Jennifer Schloss Undergrad Students