1. Metal Organic Frameworks By: Trent Benefield Group #3

2. Summary Issues to be addressed Previous method What are metal organic frameworks? How do they work? Magnetic susceptibility data Breakthrough experiments Future work Improvements Conclusions References 1

3. Issues to be addressed Hydrocracking: process of breaking down long chain hydrocarbons into smaller paraffins/olefins Performed at high temperatures Paraffins and olefins with similar boiling points need to be separated at low temperatures o ethylene/ethane, propylene/propane...etc. Large energy penalty in cooling the mixture Need energy efficient method of separating them http://en.wikipedia.org/wiki/Catalytic_reforming 2

4. Previous methods of separation Use of zeolites to separate olefins Cages are selective to certain molecules in terms of size Zeolites that adsorb propylene may not work for ethylene Can be expensive to make Need to be replaced http://pubs.rsc.org/en/content/articlehtml/2007/CC/B615661D 3

5. What are metal organic frameworks (MOFs)? Rigid, crystalline, porous, and non-interpenetrating structure with organic ligands to metal centers Structure can be intricately designed based on chemical used to make it High surface area Many types of structures and applications o Gas storage, catalysis, membranes, sensors...etc. http://www.metal-organic-frameworks.de/ 4

6. http://www.sigmaaldrich.com/materials-science/alternative-energy-materials/metal-organic-frameworks.html 5

7. Fe 2 (dobdc) dobdc 4- : 2,5-dioxido-1,4-benzenedicarboxylate Binds oxygen in side-on manner Similar structures (Mg 2+, Co 2+ ) show selectivity towards olefins over paraffins Iron framework has higher surface area and softer metal character than its counterparts 6

8. Neutron powder diffraction Similar to x-ray diffraction Cones correspond to atom spacing in structure Neutrons interact with sample o Responds to magnetism o Can "see" smaller elements o Penetrates sample throughout volume o Need large volume (~2-3 cc) http://www.ne.ncsu.edu/nrp/npdf.html 7

9. Diffraction pattern forms peaks Fit by Rietveld Method Eliminates atomic vibrations No overlapping peaks http://www.ne.ncsu.edu/nrp/npdf.html 8

10. How do they work? Side-on binding with open iron center Electron deficient iron interacts with electrons in various molecules Bonds are stronger when more electrons are available Pi-bonds most common Weaker Hydrogen bond in case of alkanes o Partial positive charge on hydrogen 9

11. Magnetic susceptibility measurements Measures sample's response to magnetic field Used a SQUID magnetometer o Superconducting Quantum Interface Device Sample is put through superconducting coils Magnetic moment is measured Magnetization and magnetic susceptibility can be derived http://www.nanomagnetics.org/instrumentation_and_chara cterization/squid_magnetometers.php 10

12. Magnetic susceptibility data was taken from the Fe 2 (dobdc) loaded with the studied hydrocarbons at different temperatures Methane, propane, ethane, propylene, ethylene, and acetylene Results show which hydrocarbon disturbs the electron density of the iron center more More disturbance=stronger interaction Olefins interact with iron center more methane<ethane<propane<propylene<acetylene<ethylene 11

13. Interactions involving paraffins decrease the ferromagnetic coupling along the ligands Interactions involving olefins reverse the coupling to anti-ferromagnetic 12

14. Pure component hydrocarbons used Initial steep slope indicates high affinity Graph approaches equilibrium value of 1 molecule of hydrocarbon/iron center Gas adsorption Isotherm 13

15. No loss in propylene uptake after 40 cycles Adsorbed at 318 K Desorbed at 373 via nitrogen purge 14

16. Breakthrough experiments Equimolar mixtures of ethylene/ethane and propylene/propane used Flow through packed bed containing the MOF Outlet gas composition analyzed by gas chromatograph equipped with flame ionization detector 99% pure ethylene/propylene has been achieved this way 15

17. Method of IAST used to simulate experiments Predictive model based on solution thermodynamics Does not require any mixture data Previous experiment simulated with excellent agreement Use IAST to compare with other materials 16

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19. Future work Interest in using MOF’s for natural gas separation Breakthrough analysis experiments carried out Cannot purify the streams simultaneously Purify in order of methane, acetylene, then ethylene/ethane 18

20. Improvements Modify metal center/organic ligands to have weaker ferromagnetic interactions Weaker interacting hydrocarbons (methane, propane) have stronger interactions Less energy input to recover gaseous hydrocarbon Alternate the pore sizes for further selectivity Easier for light hydrocarbons to adsorb onto metal sites Apply concepts used to improve zeolites Similar properties Studied for decades, while MOF’s are more recent 19

21. Conclusions Separation of similar molecular weight olefins is costly in terms of energy Metal organic frameworks are one possible solution to low energy cost separations Fe2(dobdc) is selective to olefins over paraffins Interaction with iron center o Magnetic and due to electron density Breakthrough experiments confirmed simulations Future interest in natural gas separations 20

22. References 1.Hydrocarbon Separations in a Metal-Organic Framework with Open Iron(II) Coordination Sites Eric D. Bloch, Wendy L. Queen, Rajamani Krishna, Joseph M. Zadrozny, Craig M. Brown, and Jeffrey R. Long Science 30 March 2012: 335 (6076), 1606-1610. [DOI:10.1126/science.1217544] 2.R. B. Eldridge, Olefin/paraffin separation technology: A review. Ind. Eng. Chem. Res. 32, 2208 (1993). 3.M. Eddaoudi et al., Systematic design of pore size and functionality in isoreticular MOFs and their application in methane storage. Science 295, 469 (2002). 4.S.-I. Noro, S. Kitagawa, M. Kondo, K. Seki, A new, methane adsorbent, porous coordination polymer [CuSiF6(4,4′-bipyridine)2n]. Angew. Chem. Int. Ed. 39, 2081 (2000). 5.E. D. Bloch et al., Selective binding of O2 over N2 in a redox-active metal-organic framework with open iron(II) coordination sites. J. Am. Chem. Soc. 133, 14814 (2011). 6.Z. Bao et al., Adsorption of ethane, ethylene, propane, and propylene on a magnesium-based metal-organic framework. Langmuir 27, 13554 (2011). 21

23. 7.H. Wu, W. Zhou, T. Yildirim, High-capacity methane storage in metal- organic frameworks M2(dhtp): The important role of open metal sites. J. Am. Chem. Soc. 131, 4995 (2009). 8.S. H. Hyun, R. P. Danner, Equilibrium adsorption of ethane, ethylene, isobutane, carbon dioxide, and their binary mixtures on 13X molecular sieves. J. Chem. Eng. Data 27, 196 (1982). 9.M. G. Plaza et al., Propane/propylene separation by adsorption using shaped copper trimesate MOF. Micropor. Mesopor. Mater., published online 14 July 2011. 10.L. J. Murray et al., Highly-selective and reversible O2 binding in Cr3(1,3,5-benzenetricarboxylate)2. J. Am. Chem. Soc. 132, 7856 (2010). 11.S. C. Reyes et al., U.S. Patent 12,322,364 (2009). 12.Olson; David H., U.S. Patent 6,488,741 (2001). 13.Neutron powder diffraction. Nuclear Physics Institute, ASCR Department of Neutron Physics. Web. 14 November 2012 14.Neutron Powder Diffraction Facility. ne.ncsu.edu. Web. 12 November 2012 15.Squid Magnetometers. Magnetic Materials Characterization techniques & instrumentation. Web. 10 November 2012 22

24. 16.An Ideal Absorbed Solution Theory (IAST) Study of Adsorption Equilibria of Binary Mixtures of Methane and Ethane on a Templated Carbon Jiahui Chen, Leslie S. Loo, and Kean Wang Journal of Chemical & Engineering Data201156 (4), 1209-1212 17.Hydrocarbon Separations in a Metal-Organic Framework with Open Iron(II) Coordination Sites Eric D. Bloch, Wendy L. Queen, Rajamani Krishna, Joseph M. Zadrozny, Craig M. Brown, and Jeffrey R. Long Science 30 March 2012: 335 (6076), 1606-1610. [DOI:10.1126/science.1217544] 18.Y.-S. Bae et al., High propene/propane selectivity in isostructural metal- organic frameworks with high densities of open metal sites. Angew. Chem. Int. Ed. 51, 1857 (2012). 19.A. Fürstner et al., Preparation, structure, and reactivity of nonstabilized organoiron compounds: Implications for iron-catalyzed cross coupling reactions. J. Am. Chem. Soc. 130, 8773 (2008). 23

25. http://blog.sysomos.com/2010/05/19/twittera-as-a-resource-tool/question-mark/