Greater Than the Sum of Its Parts

Newswise — The Science

By combining two catalysts at a molecular level, scientists built a system that is greater than its individual parts. By incorporating the catalytic abilities of porphyrins with sponge-like covalent organic framework (COFs), they created a structure that quickly turns carbon dioxide into carbon monoxide. The modified COFs showed great improvement in catalytic activity, including a 26-fold increase in conversion to carbon monoxide compared to the porphyrins alone.

The Impact

The modified COFs can be employed as a method for removing carbon dioxide from the atmosphere, while also generating carbon monoxide, a useful industrial feedstock product.

Summary

One of the most infamous greenhouse gases is carbon dioxide. Because of the widespread awareness of the global warming effects of carbon dioxide, a considerable scientific effort has been focused on the removal of carbon dioxide from our atmosphere. However, instead of simply removing this greenhouse gas, what if it were possible to utilize the ubiquitous amounts of carbon dioxide as an industrial source of chemical and fuel feedstocks? In particular, conversion to carbon monoxide would allow carbon dioxide to be used as a safe and abundant source of carbon for the production of a large number of chemical products. To achieve this conversion, researchers at the Lawrence Berkeley National Lab are combining the sponge-like properties of a covalent organic framework (COF) with the catalytic ability of porphyrins, ring-like organic molecules with a cobalt atom at each core. The modified and microporous COF structure provides a high local concentration of isolated cobalt ions, thus resulting in greater reactivity per cobalt. Compared to the cobalt porphyrins alone, the COFs displayed a 26-fold improvement in the yield of carbon monoxide. This remarkable catalytic activity places the COFs alongside the most efficient carbon dioxide reduction catalysts. Importantly, the COFs provide molecular control over the functionality and concentration of the reactive groups attached to the framework. This ability allows the catalytic properties of the COFs to be tuned for greater performance, a feat that the research team is currently working to achieve.

Funding

Financial support for energy catalysis in the C.J.C. laboratory was provided by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences through grant 101528-002. Financial support for covalent organic framework research in the O.M.Y. laboratory was provided by BASF SE (Ludwigshafen, Germany) for synthesis and by DOE, Office of Science, Office of Basic Energy Sciences, Energy Frontier Research Center grant DESC0001015 for adsorption and multivariate metalation. Financial support for energy catalysis in the P.Y. laboratory was supported by the Director of the Office of Science, Office of Basic Energy Sciences, Materials Science and Engineering Division, DOE, under contract no. DE-AC02-05CH11231 (Surface). E.M.N. acknowledges the National Science Foundation Graduate Research Fellowships Program for a pre-doctoral fellowship. A.R.P. acknowledges the Amgen Scholar Program for support of undergraduate summer research. We thank C. Canlas (University of California, Berkeley) for the acquisition of solid-state nuclear magnetic resonance spectra and C. Zhu at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory (LBNL) for the acquisition of grazing incidence wide-angle X-ray scattering data. X-ray absorption spectroscopy measurements were performed at the ALS. The ALS is an Office of Science user facility operated by LBNL for the DOE, Office of Science, and supported by the DOE under contract no. DE-AC02-05CH11231.

Publications

S. Lin, C.S. Diercks, Y. Zhang, N. Kornienko, E.M. Nichols, Y. Zhao, A.R. Paris, D. Kim, P. Yang, O.M. Yaghi, and C.J. Chang, “Covalent organic frameworks comprising cobalt porphyrins for catalytic CO₂ reduction in water.” Science 349, 1208 (2015). [DOI: 10.1126/science.aac8343].