By mimicking how enzymes work in living organisms, researchers have made a breakthrough that facilitates the development of cleaner catalysts to develop industrial fuels and chemicals.
Scientists have invented an enzyme-like catalyst made of soft polymers (purple) and a hard palladium core (pink). When heated, the palladium chemically converts molecules of oxygen and carbon monoxide (yellow and orange) into carbon dioxide. The reaction stops when the polymers are saturated with carbon dioxide, a strategy used by living enzymes. (Image credit: Gregory Stewart/SLAC National Accelerator Laboratory)
Researchers from Stanford University, working with scientists at the SLAC National Accelerator Laboratory, have developed a synthetic catalyst that produces chemicals in a very similar way to how enzymes do it in living organisms, researchers said. The catalyst could be used to produce methanol, an alternative to fossil fuels, using less energy and at a lower cost.
“We took our inspiration from nature,” said Matteo Cargnello, an assistant professor of chemical engineering at Stanford, in a press release. “We wanted to mimic the function of natural enzymes in the laboratory using artificial catalysts to make useful compounds.”
Enzymes are molecules that speed up biochemical reactions, and they are essential for life to exist. Cargnello’s team developed a catalyst comprised of nanocrystals of the precious metal palladium embedded in layers of porous polymers that researchers customized with special catalytic properties. Most protein enzymes found in nature also have trace metals, like zinc and iron, embedded in their core, he said.
Imitating Living Enzymes
The catalyst’s reaction to carbon dioxide was key to its similarity to living enzymes and seeing if it could achieved a desired result, researchers said. The team set out to see if its artificial catalyst would function like an enzyme by speeding up the reaction and controlling the way carbon dioxide is produced, said another of the researchers, PhD student Andrew Riscoe, in a press statement.
When heated, the palladium chemically converted molecules of oxygen and carbon monoxide into carbon dioxide, a reaction that stopped when the polymers became saturated with carbon dioxide. This ceasing of reaction is a strategy also used by living enzymes, he said.
“When an enzyme produces too much of a product, it stops working, because the product is no longer needed,” Cargnello explained. “We showed that we can also regulate the production of carbon dioxide by controlling the chemical composition of the polymer layers. This approach could impact many areas of catalysis.”
Researchers published a paper on their work in the journal Nature Catalysis.
A Focus on Natural Gas
The success of the carbon-dioxide experiment buoyed researchers to focus on converting methane into methanol, which is used widely in industry for the fabrication of textiles, plastics, and paints. Methanol also is the main ingredient in natural gas and is seen by scientists as a cleaner alternative to petroleum-based fuels, researchers said.
“The ability to convert methane to methanol at low temperatures is considered a holy grail of catalysis,” Cargnello said in the press release. “Our long-term goal is to build a catalyst that behaves like methane monooxoygenase, a natural enzyme that certain microbes use to metabolize methane.”
Currently, researchers use a two-step process to create methanol that requires heating natural gas to temperatures of about 1,000 Celsius, or 1,800 Fahrenheit. However, this process is energy-intensive and emits large amount of carbon dioxide, a known greenhouse gas.
Researchers also plan to continue their work by applying the materials they used to other systems, hoping one day to achieve artificial enzymes for myriad other applications and purposes, Cargnello said.
Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.
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