AsianScientist (Jun. 25, 2019) – Researchers in Japan have developed an organic catalyst for carbon dioxide (CO2) reduction that is inexpensive, readily available and recyclable. Their findings are published in ACS Sustainable Chemistry & Engineering.
Sustainability is a key goal in the development of next-generation catalysts for CO2 reduction. One promising approach that many teams are focusing on is a reaction called the hydrosilylation of CO2. However, most catalysts developed to date for this purpose have the disadvantage of containing metals that are expensive, not widely available and potentially detrimental to the environment.
Now, scientists led by Associate Professor Ken Motokura at Tokyo Institute of Technology, Japan, with colleagues at Japan’s National Institute of Advanced Industrial Science and Technology, have demonstrated the possibility of using a fully recyclable, metal-free catalyst.
By comparing how well different organic catalysts could achieve hydrosilylation of CO2, the team identified one that surpassed all others in terms of selectivity and yield. This catalyst, called tetrabutylammonium (TBA) formate, achieved 99 percent selectivity and produced the desired formate product with a 98 percent yield. The reaction occurred rapidly, within 24 hours, and under mild conditions at a temperature of 60°C.
Remarkably, TBA formate has a turnover number of up to 1,800, which is more than an order of magnitude higher than previously known catalysts.
“Although we did expect formate salts to exhibit good catalytic activity, TBA formate showed much higher selectivity, stability and activity that went beyond our expectations,” said Motokura.
The researchers also showed that the catalyst can be made reusable by using toluene as a solvent. They demonstrated that Lewis basic solvents such as N-methylpyrrolidone and dimethyl sulfoxide can accelerate the reaction, meaning that the catalytic system is tunable.
Furthermore, a product of the reaction, silyl formate, can be easily converted to formic acid, which is useful as a hydrogen carrier in fuel cells, for example. The high reactivity of silyl formate enables its conversion into intermediates for the preparation of organic compounds such as carboxylic acids, amides and alcohols.
“This efficient transformation technique of CO2 to silyl formate will expand the possibilities for CO2 utilization as a chemical feedstock,” Motokura added.
The article can be found at: Motokura et al. (2019) Formate-Catalyzed Selective Reduction of Carbon Dioxide to Formate Products Using Hydrosilanes.
Source: Tokyo Institute of Technology; Photo: Shutterstock.
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