Metal-Organic Frameworks (MOFs) as low temperature adsorbents for carbon dioxide.

1. Metal-Organic Frameworks (MOFs) as low temperature adsorbents for carbon dioxide. SINTEF Materials and Chemistry, Dept. of Hydrocarbon Process Chemistry, Oslo, Norway Centre for Materials Science and Nanotechnology and Department of Chemistry, University of Oslo, Norway

2. SINTEF Dr. Bjørnar Arstad Aud M. Bougza Dr. Richard Blom Dr. Richard H. Heyn Aud I. Spjelkavik Dr. Ole Swang University of Oslo Prof. Helmer Fjellvåg Dr. Kjell Ove Kongshaug (post-doc) Financing Norwegian Research Council Climit Program (grant number 151502/210) Alstom Statoil UOP Acknowledgements

3. Source: Canadian Clean Power Coalition Background/motivation • The obvious… • Removal of CO2 from gas streams: flue gas (4-14%), natural gas (2-50%) • Present technology: Temperature-swing process utilizing amines in an aqueous solution • Weaknesses: Energy efficiency, Chemical stability, Environmental issues, Absorbent costProcess cost • Solid sorbents! Can a better process be developed basedon solid sorbents? • Possible weaknesses: Heat transfer, Sorbent cost (?), powder transfer or gas switching (?)

4. Why MOFs? • A number of modified mesoporous materials have been studied as CO2 absorbents • Advantages of MOFs • Highly crystalline  Similar to zeolites • Highly porous  Much more diverse! • A MOF material has the world record in powder specific surface area: > 6000 m2/g! • Rational design of MOF structures is (still) not fully possible (mostly black-box synthesis….) So, what is a MOF?

5. MOF basics: MOF= Metal Organic Frameworks; organic-inorganic hybrid materials Metal centre or cluster(inorganic part) Metal Organic Framework(coordination polymer) Linker(organic part) → +

6. Ni(NO3)2 + AlCl3 + InCl3 + + USO-1-Al (MIL-53) USO-2-Ni USO-3-In (MIL-68) 1925 m2/g 930 m2/g 1300 m2/g MOFs of the present study:

7. Amine functionality: • Via analogy with soluble amine based absorption systems; stronger bonding through carbamate formation, etc… vs However, MOF synthesis is affected by the presence of amine functionality:

8. Isotherms at low p: • Despite lower spec. surf. areas – the amine functionalized MOFs have higher CO2 capacities at low CO2 pressures

9. Comparison with other solid adsorbents:* * Comparable data only at low pressures.

10. Adsorption at increase pressure: MOF-177 (147 wt %) Zeolite 13X Carbon Empty Millward & Yaghi, JACS, 2005; 127, 14142 MOF-177 – SSA = 4500 m2/g Kitagawa, Kitaura & Noro, Angew. Chem., int. ed. 2004, 43, 2334

11. Our MOFs at elevated pressures: • CO2 adsorption > 60 wt% (based on dry adsorbent) is measured. • Maximum capacity seems to be directly proportional to the pore volume of the adsorbent used. • Data fits well with the pores being filled with liquid CO2 at room temperature Figure: High pressure isotherms of USO-1-Al and USO-2-Ni

12. BreakthroughCurves 6.5 % CO2 3.1 wt % absorbed 2.7 wt % desorbed USO-1-Al, T = 50 °C, 8 % CO2, approx. equimolar amounts of other components

13. But with water … • H2O is a (much) better adsorbent than CO2 USO-1-Al, T = 50 °C, 8 % CO2, approx. equimolar amounts of other components

14. Conclusions • Low CO2 pressures:- MOFs show CO2 adsorption capacities among the best reported (at low pressures)- Amine functionalities increases the CO2 capacity at low CO2 pressures - Water is a preferred absorbant • High CO2 pressures (up to 25 atm):- very high CO2 capacities of MOFs are observed.- maximum capacity dependent on pore characteristics such as pore volume and surface area. • MOF based adsorbents might find applications within PSA processes for dry gas mixtures