Graduate Student Tom Corey

"Increased Catalytic Performance Using Porphyrin Linked Metal-Organic Frameworks for the Electrochemical Reduction of CO2"

It is practically universally agreed upon among scientists that the climate is warming and needs immediate and pronounced attention to slow or reverse this dangerous trend. Each year, billions of tons of greenhouse gases are released into our atmosphere from many different sources around the globe1, of which approximately 75 percent is carbon dioxide (CO2).2 Despite some of the already ominous signs from nature, year after year records are set for the amount of greenhouse gases that are spilled into our skies with remediation efforts falling well short of what is necessary to keep up, let alone gain ground.3 As a result, increasing temperatures are being observed all around the globe as a normal expectation. In the hopes to make a global difference, the search for an energy efficient catalyst capable of reducing CO2 is paramount. A new approach to solving this man-made problem is looking to one of nature’s designs. Plants harvest the sun’s radiation to drive the CO2 reducing process of photosynthesis. Within plants, chlorophyll and more specifically the porphyrin structure on the chlorophyll molecule, has been found to be an energy gathering mechanism.4 Metal-organic frameworks (MOFs) were first introduced in the 1990s and are known for their strong redox potential as well as superior surface areas. Despite these properties, their application for the reduction of CO2 has been limited. Combining MOF structures with light harvesting porphyrin linking units has led to several novel materials. These new materials which contain various metal catalysts within them have been examined for their feasibility for reducing CO2 gas into useful products. Advances in the combination of these favorable physical and electrical characteristics result in CO2 reduction rates as high as 35 times higher than using the MOF or linker alone and represents as much as a 13 fold increase in solar efficiency since 2015.5 It is evident with modifications such as changes in the MOF structure, temperature, pH and type of solvent, the end product can be selectively chosen to help reduce the need for further processing. The realization of an effective sunlight driven catalytic CO2 reduction process will not only provide a source of renewable energy, but will also reduce the effects of global warming while providing a safer world for future generations.

(1) Greenhouse gas emissions https://ourworldindata.org/greenhouse-gas-emissions (accessed Nov 2, 2020).
(2) US EPA, O. Global Greenhouse Gas Emissions Data https://www.epa.gov/ghgemissions/global-greenhouse-gas-emissions-data (accessed Nov 2, 2020).
(3) Analysis: How much ‘carbon budget’ is left to limit global warming to 1.5C? https://www.carbonbrief.org/analysis-how-much-carbon-budget-is-left-to-l... (accessed Nov 2, 2020).
(4) Structure and Reactions of Chlorophyll https://www.ch.ic.ac.uk/local/projects/steer/chloro.htm (accessed Nov 2, 2020).
(5) Wang, Z.; Zhou, W.; Wang, X.; Zhang, X.; Chen, H.; Hu, H.; Liu, L.; Ye, J.; Wang, D. Enhanced Photocatalytic CO2 Reduction over TiO2 Using Metalloporphyrin as the Cocatalyst. Catalysts 2020, 10 (6), 654. https://doi.org/10.3390/catal10060654.