Copper Nanocrystals Encapsulated in Zr-based Metal-Organic Frameworks for Highly Selective CO2 Hydrogenation to Methanol

Significance Statement

Methanol produced by the process of hydrogenation of carbon dioxide is a route to recycle the captured carbon dioxide from fossil fuels. This is a convenient fuel to transport as a hydrogen-rich source and it is also applied as a chemical feedstock to manufacture key chemical components. Generally, methanol is manufactured from synthesis gas using a Cu/ZnO/Al2O3 catalyst. On the other hand, isotope labeling experiments revealed that carbon dioxide is main carbon source for production of methanol and carbon monoxide is responsible for the active oxidation state of copper. Finding catalysts that utilize carbon dioxide and hydrogen as sources to produce methanol selectively is desirable, however, this remains a challenge.

Researchers led by professors Omar Yaghi, and Gabor Somorjai, from the University of California Berkeley and Lawrence Berkeley National Laboratory reported a catalyst composed of copper nanocrystals encapsulated within a metal-organic framework for the hydrogenation of carbon dioxide to methanol with 100% selectivity and high activity. Their work is now published in peer-reviewed journal, Nano Letters.

Carbon dioxide hydrogenation to methanol reaction is known to be structure sensitive in that the catalytic properties are linked with the dimensions as well as composition of the metal oxide- metal interface. Metal-organic frameworks are important in this instance for interfacing with other active metals owing to their nanosized metal oxide secondary building units and tunability of their composition. This allows for investigating the effects of a catalytic interface.

In their setup, an ordered array of Zr oxide secondary building units were precisely placed on the copper surface leading to high interfacial contacts between copper nanocrystals and Zr oxide secondary building units. The Zr oxide secondary building units were spatially spaced by organic linkers to ensure the accessibility of reactants to active sites.

The synthesis procedure for copper nanocrystals capped with polyvinylpyrrolidone using polyol process enabled the researchers to study systematically the change in the catalytic attributes as a function of various metal-organic frameworks and other supports. The pre-synthesized copper nanocrystals were added to a solution composed of metal-organic framework precursors. Besides the exclusion of oxygen to avoid the surface oxidation as well as acid-mediated dissolution of copper nanocrystal, they realized that the selection of metal precursors affected the encapsulation process.

Copper catalyst for the carbon dioxide hydrogenation to methanol was done over various types of metal-organic frameworks. The authors found UiO-66 to be the best promoter for copper catalyst resulting in high selectivity and high production of methanol from carbon dioxide. From XPS analysis, the presence of a combination of multiple copper oxidation states derived by high interfacial contact area between copper nanocrystals and Zr oxide secondary building units of the metal-organic framework lead to the high turnover frequency of methanol production. This was the first finding that metal oxide clusters in metal-organic framework can have strong-metal support interaction as typically observed in bulk metal oxides.

Copper Nnanocrystals Encapsulated in Zr-based Metal-Organic Frameworks for Highly Selective CO2 Hydrogenation to Methanol - Advances in Engineering

About The Author

Dr. Jayeon Baek is currently a postdoctoral fellow in Department of Chemistry at UC Berkeley, working in both Profs. Gabor A. Somorjai’s and Omar M. Yaghi’s groups. She received her Ph.D. degree from School of Chemical and Biological Engineering, Seoul National University in 2015, and B.S. degree in Department of Chemistry from Ewha Womans University in 2009. Her major research interests include heterogeneous catalytic conversion of natural gas, carbon dioxide, and biomass into value-added chemicals. Her current research focuses on the design of metal-organic framework (MOF) for gas-phase methanol synthesis.

About The Author

Bunyarat Rungtaweevoranit was born in Bangkok, Thailand. He obtained his B.Sc. (Chemistry) and M.Sc. (Organic Chemistry) from Mahidol University, Thailand. He is currently a Ph.D. candidate in Prof. Omar M. Yaghi group at University of California, Berkeley. His research interests encompass the development of metal–organic frameworks (MOFs) and related materials for catalysis.

About The Author

Prof. Gabor A. Somorjai received his Ph.D. in Chemistry from the University of California (UC), Berkeley in 1960. He joined the IBM research staff until he was appointed as an Assistant Professor of Chemistry at UC Berkley in 1964 and was later promoted to Professor in 1972. He is also University Professor of the UC system from 2002. Concurrent with his faculty appointment, he is a Faculty Senior Scientist in the Materials Sciences Division, and Group Leader of the Surface Science and Catalysis Program at the Center for Advanced Materials, at the E.O. Lawrence Berkeley National Laboratory.

Professor Somorjai’s research interest is in the fields of the structure of surface, catalytic atomic and molecular structure of surfaces and adsorbed molecules, and catalytic reactions on surfaces as solid-gas and solid-liquid interfaces. He is studying the integration of heterogeneous, homogeneous, and enzyme on the molecular scale. His studying utilizes transition metal and oxides and metal-organic frameworks (MOFs). The instruments utilized in his laboratory provide structure, kinetics, and information on the catalytic reaction condition on the molecular scale using laser spectroscopy synchrotron based technique and scanning tunneling microscopy.

Professor Somorjai has educated more than 130 Ph.D. students and 250 postdoctoral fellows. He is the author of four textbooks and more than 1200 scientific papers in the fields of surface chemistry, heterogeneous catalysis, and solid state chemistry.

About The Author

Prof. Omar M. Yaghi received Ph.D. in Inorganic Chemistry from University of Illinois at Urbana-Champaign in 1990. He was an NSF Postdoctoral Fellow at Harvard University during 1990-1992. He started his independent career as an Assistant Professor in 1992 at Arizona State University, moved to University of Michigan at Ann Arbor as Robert W. Parry Professor of Chemistry in 1999, and then UCLA in 2006 as Christopher S. Foote Professor of Chemistry and Irving and Jean Stone Chair Professor in Physical Sciences. Since 2012 he has been the James and Neeltje Tretter Chair Professor of Chemistry at University of California, Berkeley, and a Senior Faculty Scientist at Lawrence Berkeley National Laboratory. He is the Founding Director of the Berkeley Global Science Institute, and the Co-Director of the Kavli Energy NanoSciences Institute, and the California Research Alliance by BASF.

He is widely known for the discovery and for pioneering the development of several extensive classes of new materials: Metal-Organic Frameworks (MOFs), Covalent Organic Frameworks (COFs), and Zeolitic Imidazolate Frameworks (ZIFs). These materials have the highest surface areas known to date, making them useful in many applications including the (1) storage and separation of hydrogen, methane, and carbon dioxide, (2) conversion of carbon dioxide to fuels and high value chemicals, (3) capture of water from air for fresh water production, (4) highly selective cleavage of peptides using enzyme-inspired catalysis, and (5) storage of ions in supercapacitor devices, and transport of protons and electrons in conductive frameworks.

Reference

Bunyarat Rungtaweevoranit1,2, Jayeon Baek1,2, Joyce R. Araujo1,3, Braulio S. Archanjo3, Kyung Min Choi1,2, Omar M. Yaghi1,2,4, and Gabor A. Somorjai1,5. Copper nanocrystals encapsulated in Zr-based Metal-Organic frameworks for highly Selective CO2 hydrogenation to Methanol. Nano Letters, volume 16 (2016), pages 7645-7649.

Show Affiliations
  1. Department of Chemistry, University of California−Berkeley, Kavli Energy NanoSciences Institute, Berkeley, California 94720, United States.
  2. Materials Sciences Division and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
  3. Materials Metrology Division, National Institute of Metrology, Quality, and Technology, Duque de Caxias, Rio de Janeiro 25250−020, Brazil.
  4. King Abdulaziz City for Science and Technology, Riyadh 11442, Saudi Arabia.
  5. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.

 

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