ENRICHING SOCIETY
A TANKFUL OF
SUNSHINE
Taking cues from plants to produce fuel for the future .
BY SUSAN BROWN
WHAT IF WE COULD WRING LIQUID FUEL FROM SUNLIGHT ? What if chemists could capture energy from our nearly inexhaustible star and store it in the chemical bonds of hydrocarbon fuels , like gasoline ?
Plants have been doing something like this for billions of years through photosynthesis . Plants harvest solar energy and use it to power a chemical chain reaction that makes sugars , or in other words , their “ fuel .”
Inspired by those leafy green powerhouses , UC San Diego scientists are working to develop a system they call “ artificial photosynthesis .” The process will likewise use sunlight to create a chemical reaction that creates energy , only instead of plant‐powering sugars , the product will be high-density fuel .
The effort is led by Cliff Kubiak , UC San Diego distinguished professor of chemistry and biochemistry , and a member of the Joint Center for Artificial Photosynthesis , a multi-university innovation hub funded by the Department of Energy to create alternative fuels .
Kubiak and colleagues are working on ways to loosen the tenacious bonds in carbon dioxide molecules so that the atoms therein can be reassembled into liquid fuels . Plants do this naturally via enzymes , yet these enzymes are high-maintenance proteins that must continually be replenished — not so easy to recreate artificially .
Kubiak and colleagues are developing a more efficient system that replaces those unwieldy proteins with chemical structures that serve like scaffolding . Kubiak likens these “ metal-organic frameworks ,” or MOFs , to the mix-and-match children ’ s building kits we all know as Tinkertoys .
“ They ’ re modular — we can put whatever catalyst we want in there and then it ’ s nailed down into this robust , solid-state structure ,” he says . “ We decided to use the MOF as a platform for making things that are like enzymes but aren ’ t floppy peptides that can degrade .”
Along with Seth Cohen , another chemistry professor at UC San Diego , the team created an MOF that allowed them to infuse the “ scaffolding ” struts with a photosensitive chemical , akin to chlorophyll and other pigments that nature uses for photosynthesis . When light shines on the setup , the electrons shuffle and carbon dioxide molecules recombine with hydrogen to form nascent molecules of fuel .
This particular MOF is just one possibility in the progress toward achieving viable products that create fuel via artificial photosynthesis . “ There ’ s going to be a lot more ,” Kubiak says . “ We ’ re doing such new things that there are still broad strokes to contribute .”
14 TRITON | SPRING 2016