Trees: The Ultimate Chemists. How Trees Inspire Me to Do Better Chemistry

When I talk to people about my research, I have found that it is not usually very helpful to say that I am an organometallic chemist or (worse) to say that I synthesize carbon dioxide complexes of molybdenum and tungsten. Instead, I usually start by talking about trees. Most people know about photosynthesis and that a tree, like all plants, harnesses the energy from light to grow. Some people even know that the whole body of the tree: its leaves, trunk, roots and all its branches are made primarily of carbon. Where does the tree get all of this carbon? From the air. The tree uses the energy it collects during photosynthesis to convert carbon dioxide from the air into sugar (eg. glucose)— molecules it can then use as building blocks to build itself into the tree that it will be.

But what does a tree’s biology have to do with my research? Quite simply, as a chemist I am inspired by the tree’s ability to do amazing chemical reactions. Converting carbon dioxide into carbohydrates is a surprisingly difficult process. Right now if I want to make a compound in the lab similar to what a tree can make, I can’t just walk into the lab and do a reaction using carbon dioxide as the starting material. Instead, I would select an easier-to-use starting material. In doing so, I would again take advantage of the work of plants: typical chemical starting materials are mostly derived from (plant) fossil fuel sources like petroleum. These carbon starting materials are easy to get these days because of our world’s dependence on petroleum and natural gas for energy. The extraction of oil and gas, most of which is used for energy, also produces lots of byproducts which then are used as starting materials by chemists to make plastics and pharmaceutical products. Naturally, it would be far better if we as chemists could cut out the middle man and make these incredibly useful products without relying on the extraction of oil and gas. However, we don’t know how to do the chemistry. We can’t really do much chemistry with carbon dioxide. We don’t have the chemical expertise of a tree.

Carbon dioxide presents such a challenge because of its stability. When you burn the gas in your car, the main carbon product is carbon dioxide, because that form of carbon is so stable. That is also why we have too much carbon dioxide in our planet’s atmosphere and why it is such a gargantuan task to try to reduce the amount of carbon dioxide emitted into the atmosphere. Carbon dioxide is easy to make, and because of that it is also very hard to use to make things. That inherent stability is why we as chemists need carbon dioxide activation. Activation refers to a process that takes a very stable compound like carbon dioxide and makes it more likely to undergo a reaction. If you activate carbon dioxide, then you have a better chance of turning it into something else.

One way to activate carbon dioxide is to use a catalyst. A catalyst can change everything! It might allow what was once impossible, using carbon dioxide as a starting material, possible. Trees have complex pathways that make use of many biochemical catalysts (enzymes) in sequence to accomplish carbon dioxide activation, which is often called carbon fixation in the context of photosynthesis. Potential catalysts compounds, biochemical or otherwise, often contain metals like molybdenum or nickel. Thus, as an organometallic chemist who wants to do carbon dioxide activation, I hope to learn how to go into the lab and make a catalyst, containing for example molybdenum, that could activate carbon dioxide. If we can do that, then we as human chemists will have learned how to do chemistry a little bit better by taking inspiration from the trees.

Joining the Lee Lab at Seoul National University to continue working in the area of carbon dioxide activation is very exciting. At SJU, my students and I have focused on synthesizing potential catalysts featuring the metals molybdenum and tungsten. The Lee Lab focuses on potential catalysts featuring the metal nickel. I am looking forward to working with different metal systems to accomplish the same overall goal – doing better chemistry just like the ultimate chemists: trees.