A research team from the US Energy Department’s Lawrence Berkeley National Laboratory has figured out what to do with the carbon dioxide from industrial emissions: take that nasty flue gas and convert it into carbon monoxide, which can then be turned into useful products such as plastics. Carbon recycling sure beats sequestration for a long term, sustainable solution to global carbon overload, and it makes a lot more sense to recycle used carbon than to continue digging new carbon up out of the ground.
The foundation for the new carbon capture system is something called COFs, or covalent organic frameworks. Think of a sponge with a crystalline structure and you’re on the right track. COFs are like hugely complicated sponges, with a tightly folded framework that hides an enormous surface area.
How enormous? According to Berkeley Lab, if you unfolded a COF the size of a sugar cube, it would cover a football field.
COFs were first developed at the University of Michigan back in 2005, when researchers “coaxed” rigid plastics to organize into predictable crystal structures — something that had never been done before. The research team did it by slowing down the reaction time involved in synthesizing rigid plastics.
Unlike their cousins, MOFs (metal organic frameworks), COFs contain no metal. They are much lighter because they are typically made of light elements such as hydrogen, boron, carbon, nitrogen and oxygen. Their properties can also be tweaked and tailored by adjusting the angles at which the “hubs” and “struts” connect.
The University of Michigan project was partly intended to design COFs for storing hydrogen in anticipation of a sparkly green hydrogen powered future, which is a future not everyone anticipates. Carbon capture and recycling may prove to be somewhat less controversial.
COFs are already useful in carbon capture, but the problem remains of what to do with the carbon, and how to do it in a commercially viable system.
The new Berkeley Lab carbon capture project solves that problem by tweaking COFs to form an integrated system that can catalyze carbon dioxide instead of just trapping it.
That’s where the “net” comes in. The research team deployed a new technique developed at UCLA called reticular chemistry, which involves this:
…chemists are able to predictably assemble molecular building blocks into predetermined structures which can be functionalized and their metrics altered at will. We call this new kind of chemistry ‘reticular chemistry’ to emphasize that the dream of designing large and extended structure is becoming a reality.
The reticular chemistry approach enabled the team to “stitch” netlike structures embedded with a catalyst called porphyrin. Porphyrins have the particular talent of transporting electrons to carbon dioxide and that’s where the magic happens, according to the research team:
Because the porphyrin COFs are stable in water, they can operate in aqueous electrolyte with high selectivity over competing water reduction reactions, an essential requirement for working with flue gas emissions.
So far, tests have confirmed that the porphyrin COFs perform “exceptionally” well in terms of catalytic material:
…one porphyrin COF can reduce 290,000 molecules of carbon dioxide to carbon monoxide every second. This represents a 26-fold increase over the catalytic activity of molecular cobalt porphyrin catalyst and places porphyrin COFs among the fastest and most efficient catalysts of all known carbon dioxide reduction agents.
As long as you don’t poison yourself with it, carbon monoxide has numerous useful purposes in industrial processes as well as plastics manufacturing, so yes it’s kind of like Darth Vader leaving the dark side behind and doing something nice for a change.
Onwards And Upwards For Carbon Capture
The Berkeley carbon capture innovation is still in the early stages of development. The next steps include ramping up the process efficiency and deriving additional value-added carbon products from COFs.
While that’s happening, the Energy Department seems determined to get the general carbon recycling idea to market. There is at least one other carbon conversion project going on at Energy Department labs, and last year the agency pumped $4 million into a New Zealand carbon capture startup, luring the company over to Illinois and enabling it to start its gas-to-liquid fuel technology onto a commercial track.
Other recent developments include a gas-to-fuels company that deploys solar energy to power the process. We’ve also been following a gas-to-plastics company called Newlight Technologies, which has been busy signing deals for its AirCarbon product over the summer, including one with The Body Shop.
As for other forms of carbon sequestration, four years ago our sister site Planetsave pointed out that drought could put a crimp in biomass carbon capture in the US, and earlier this year the Obama Administration pulled the plug on the US coal industry’s showcase $1 billion “clean coal” FutureGen carbon capture and sequestration project, which ended up proving that underground carbon storage is a bad idea.
Image credits: top via Berkeley Lab (conceptual model showing how porphyrin COFs could be used to split CO2 into CO and oxygen courtesy of Omar Yaghi; bottom via University of Michigan (crystalline sheets produced in covalent organic frameworks by Adrien Côté).
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