Useful chemicals and fuel from carbon dioxide

Carbon dioxide is an abundant, non-toxic, inexpensive, and renewable source of carbon. This makes CO2 the most coveted compound by Green Chemistry enthusiasts. Industries are always on the lookout for ways to enable the effective use of to act as synthetic building blocks for producing fuels like Methane, Di-methyl-ether, and Methanol fine-chemicals. Furthermore, CO2 conversion could also help reduce atmospheric CO2 levels, popularly known as “Green House Gas”, and thus, protect the climate.

Nature has been highly successful in using CO2 as synthetic building blocks in photosynthesis. For decades, scientists have been trying to understand this phenomenon at a molecular level. Such studies have proved useful in developing biomimetic catalysts for CO2 conversion. Chlorophyll (Porphyrin molecules) in green plants convert incident sunlight and atmospheric CO2 into sugars (energy). So, this makes them a promising target for testing activation catalysts for CO2 adsorption. Effective CO2 adsorption using man-made catalysts is indeed our end-goal. Much research is being conducted in this area to further the economic viability of the processes that utilize CO2. Several companies are pursuing the idea/concept of thermochemical and electrochemical conversion of CO2 into chemical feedstock or polymers. Research and development are currently focused on increasing the catalyst life and bringing down the temperature of conversion.

Future research must emphasize the rational design of highly active catalysts to satisfy the economic development of CO2 conversion. However, the development of such efficient catalysts requires a complete understanding of CO2 and CO2-catalyst interactions.

In order to develop such a catalyst, the following points should be considered,

1. CO2 has a strong affinity towards nucleophiles and electron-donating reagents due to its carbonyl-carbon's electron deficiency; if the designed catalysts has nitrogen or base-functionality (basic), it will have an increased affinity towards CO2 (e.g., Porphyrin, Grignard reagents).
2. With low-valent metals and alkene, CO2 undergoes “oxidative cycloaddition.”
3. New CO2 soluble catalysts may increase efficiency.
4. Homogeneous catalysis in compressed CO2 may increase selectivity.
5. The catalyst in supercritical CO2 may also increase stability. It is essential to use CO2, based on the unique physical properties as that of the supercritical fluid, either as a solvent, or as an anti-solvent, or reactant, or a combination of all.
6. Photoelectrochemistry, the study of using solar energy to split CO2, is an emerging method for clean production of chemicals. It is also essential to develop catalysts (Semiconducting materials) for the electrochemical conversion of CO2.
7. The use of high-energy starting materials may ease the catalyst role.
8. The catalyst will be more efficient if it has both CO2 adsorption and activation functionality. E.g., designer MOF that contains Lewis-base sitewill donate electron to CO2, in contrast to the Lewis-acids sites in traditional MOFs for adsorbing CO2.
9. A computational tool such as Density Function Theory (DFT) may help improve the catalytic activity or find a new catalyst.
10. Chemical reactions can also benefit from using CO2 as a mild oxidant or as a selective source of O2 atoms because dissociation of CO2 on a catalyst-surface could produce active O2 species.

The trend towards converting CO2 to valuable chemicals and fuels will probably intensify in the near future. This could, in turn, lead to effective management to tackle climate change and the energy crisis.

As Whitesides emphasizes, managing CO2 and conversion into valuable chemicals and energy will be the reinvention of chemistry, and it is also a chemistry/ molecular solution to the critical problem facing society. He says

 “Some of the most interesting problems in science, and many of the most important facing society, need chemistry for their solution. Examples include: understanding life as a network of chemical reactions; interpreting the molecular basis of disease; global stewardship; the production, storage, and conservation of energy and water; and the management of carbon dioxide."

Issues pertaining to CO2 are truly global and a major opportunity to develop sustainable energy options and environmental preservation. So, the use of CO2 to synthesize useful chemicals & fuels will mark a new field in chemistry. It is important to establish university-industry-collaboration to search for new-reactions & new-catalysts in this field.