Metal Organic Frameworks as Catalysts in the Conversion of CO2 to Cyclic Carbonates Moises A. Carreon University of Louisville Chemical Engineering Dept. macarr15@louisville.edu
2013 Kentucky Innovation & Entrepreneurship Conference. Lexington KY
August 29, 2013
Global Carbon Dioxide Emissions
CO2 emission almost tripled from 1965 to 2011
Carbon Dioxide Emissions by region
Solution??? Chemicals !!! ‌‌
Glacier melting Global warming
Conversion of CO2 into useful chemicals
Types of CO2 Transformation
T. Sakakura, J.C. Choi, H. Yasuda Chem. Rev. 2007, 107, 2365
Why CO2 conversion to chemicals? There are several motivations for producing chemicals from CO2 : (1) CO2 is a cheap, non-toxic and non-flammable feedstock that can frequently replace toxic chemicals such as phosgene or isocyanates. (2) CO2 is a totally renewable feedstock compared to oil or coal. (3) The production of chemicals from CO2 can lead to totally new materials such as polymers. (4) New routes to existing chemical intermediates and products could be more efficient and economical than current methods. (5) The production of chemicals from CO2 could have a small but significant positive impact on the global carbon balance.
Useful Products Obtained from Carbonates and Carbamates
Carbonates
polar aprotic solvents electrolytes in secondary batteries precursors for polycarbonate materials
Carbamates
polyurethanes pesticides fungicides medicinal drugs synthetic intermediates
Conventional Catalysts for Carbonate Synthesis Catalyst
Disadvantages toxic, water- and air-sensitive, causing handling problems and requiring high temperature/pressure
Metal complexes Schiff bases, phthalocyanines
porphyrines
and
requiring an additional cocatalyst
Metal oxides
weakly active, requiring a very high catalyst/substrate ratio, a substantial amount of solvent and long reaction times
Quaternary ammonium salts
requiring high temperature/pressure
Mesoporous materials
requiring high temperatures and a functional group
Zeolites
requiring high temperature
The need for novel Catalysts‌‌‌.. The development of superior performance catalysts requires novel materials with fundamentally different structural, compositional, adsorption and transport properties than those of conventional zeolites, metal oxides or metal phases. In this respect, metal organic frameworks (MOFs) have emerged as novel crystalline microporous materials with highly desirable properties, such as uniform micropores, high surface areas and open porous framework structures with large accessible pore volumes making them potentially interesting candidates for catalytic applications.
Catalytic Conversion of CO2 to Carbonates
O O
+
MOF
CO2
R
O
O
R Epoxide
Cyclic Carbonate
R = -CH3, -CH2Cl, -C6H5
MOFs are ideal materials to effectively catalyze this reaction
What is a MOF?
Metal building block (ZnN4)
Organic linker
MOF
MOFs are novel type of crystalline porous materials with highly desirable properties, such as uniform micropores, high surface areas, and exceptional thermal and chemical stability.
ZIF-8 an appealing MOF catalyst for cyclic carbonates synthesis ZIF-8 is an appealing material to employ as catalyst for CO2 conversion
1. Preferential high CO2 adsorption capacity (Ideal catalysts for the conversion of CO2 to cyclic carbonates should be those exhibiting high CO2 uptakes) 2. The presence of Lewis acid sites in its framework (Lewis acid sites are known to catalyze the reaction of CO2 with epoxides to give propylene carbonates and other precursors of polycarbonates ) (a)
(b)
(c)
O=C=O
Lewis acid site (Zn or Cu)
CO 2 adsorption
Surface Reaction O=C=O
O=C=O
Lewis acid Organic linker site O=C=O
ZIFor orCu Bio(BTC) -MOF ZIF-8 ZIF-8 3 2 ZIF-8 Structure
CO 2 adsorbs at basic units of the organic linker
CO 2 reacts at Lewis acid sites
(a) Main components of ZIF-8, (b) CO2 adsorbing at the organic unit sites, (c) Adsorbed CO2 reacts at the Lewis acid sites.
ZIF-8 crystals ( synthesis and characterization) (0 1 1)
(1 1 4) 20
(0 4 4) (2 4 4) (2 3 5)
15
(2 3 3) (1 3 4)
10
b
013 112 011
(1 1 2) (0 2 2) (0 1 3) (2 2 2)
(0 0 2)
Intensity (a.u.) 5
235 134 233
a
25
30
002 022 222
35
2θ (degree)
244
c
d
e
380
Adsorption capacity (mmol/g)
Quantity adsorbed (cm3/g STP)
2 nm
360 340 320 300 280 0
0.2
0.4
0.6
0.8
Relative Pressure (P/Po)
1
CO2/CH4 ratio = ~14
2.5
f
2 1.5 1 0.5 0 0
30
60 90 Pressure (KPa)
We have developed in our lab “wet-chemistry routes” to prepare ZIF-8 crystals with controlled crystal size
120
Catalytic performance of ZIF-8 in the Conversion of CO2 to Chloropropene Carbonate
Epichlorohydrin CO2
Chloropropene Carbonate
P,T, time
ZIF-8
ZIF-8 an effective catalyst for carbonate synthesis
The conversion of epichlorohydrin reached a maximum of ∼100% at 100 °C, while the selectivity to chloropropene carbonate decreased. The highest chloropropene carbonate yield was observed at 80 °C.
Mechanism for CO2 conversion to cyclic carbonates over MOFs (b)
(a) Acid site
Basic site
O=C=O
O O
O=C=O
R
R
O
-
O
O
O
O=C=O
R
R (d)
(c)
Reaction mechanism for the catalytic conversion of CO2 and epoxides to cyclic carbonates over MOFs: (a) adsorption steps, (b) nucleophilic attack, (c) ring opening, (d) ring closure.
MOFs as catalysts for the synthesis of carbonates
Conclusions 1. The utilization of CO2 as a renewable raw material for the production of chemicals is an area of great societal importance. 2. In particular, the catalytic conversion of CO2 into cyclic carbonates, which are useful chemical intermediates employed for the production of plastics and organic solvents, represents an appealing approach for the efficient use of CO2. 3. Metal organic frameworks MOFs, have emerged as novel porous materials which combine highly desirable properties, such as uniform pores in the micro and mesoscales, high surface areas, flexible chemistries, and exceptional thermal and chemical stability, making them ideal candidates for catalytic applications. 4. The catalytic ability of these porous materials for the synthesis of cyclic carbonates from CO2 have been presented. 5. Surface features of the MOFs such as acidity (presence of acid sites), and adsorption selectivity (presence of basic sites), as well as textural features such as surface area, pore size, and pore volume play a critical role on the overall catalytic performance of these porous phases.
Representative Publications •1) M. Zhu, D. Srinivas, S. Bhogeswararao, P. Ratnasamy, M.A. Carreon*, Catalytic activity of ZIF-8 in the synthesis of styrene carbonate from CO2 and styrene oxide”, Catalysis Communications 2013, 32, 36-40. • 2) E.E. Macias, P. Ratnasamy, M.A. Carreon* “Catalytic activity of metal organic framework Cu3(BTC)2 in the cycloaddition of CO2 to epichlorohydrin reaction” Catalysis Today 2012, 198, 215218. • 3) M.A. Carreon * “Metal Organic Frameworks as Catalysts in the Conversion of CO2 to Cyclic Carbonates” In. J. Chem. A (invited) 2012, 51A, 1306-1314 • 4) C. Miralda, E.E. Macias, M. Zhu, P. Ratnasamy, M.A. Carreon*, “Zeolitic imidazole Framework-8 catalysts in the conversion of CO2 to chloropropene carbonate” ACS-Catalysis 2012, 2, 180-183.
Acknowledgements Personnel: Ms. Minqi Zhu Ms. Carmen Miralda Ms. Zhenzhen Xie Mrs. Eugenia Macias
Collaborators: Dr. P. Ratnasamy (Conn Center) Dr. D. Srinivas (NCL, India)
Funding: KSEF -2361-RDE-014 Mahendra Jain Maria Labreveux Spring 2013. Graduate research group: Carmen Miralda, Zhenzhen Xie, Minqi Zhu, Moises Carreon, Masoudeh Ahmadi, Hugo Nambo, Joseph Bohrman (not pictured), Eugenia Macias (not pictured)