Electrochemical reduction of CO2 to valuable carbon-based products is an elegant strategy towards reducing atmospheric CO2 and providing clean energy, thus mitigating global warming. In the search of novel materials for CO2R, metal organic frameworks (MOFs) show a great potential, as they combine the main advantages of homogeneous and heterogeneous catalysts. We show that aluminum confined in a MOF, MIL-53(Al), can electrochemically reduce CO2 to both CO and formic acid, as valuable carbon-based products. This aluminum MOFs can produce up to to 21% for CO production and 19% for formic acid production, and with a turnover frequency of 174 h-1. CO is a valuable intermediate in chemical synthesis and towards all other observed products in electrochemical CO2R, including ethylene and ethanol. It is also currently used in the formation of hydrocarbon through Fischer-Tropsch chemistry. Formic acid is also an attractive product because it can be used as a fuel with practical application in hydrogen storage and direct formic acid fuel cells. To the best of our knowledge, MIL-53(Al) is the first reported MOFs that produce both CO and formic acid. While Al as a foil is inactive for CO2 reduction and shows high selectivity for the hydrogen evolution reaction, Al centers confined in MIL-53 suppress HER activity and interestingly enhance CO2R. This study demonstrates that confined metal centers in organic frameworks can impart atypical CO2 reducing capability to metals that traditionally do not favor electrochemical CO2 reduction.

Confining aluminum in metal–organic framework triggers carbon dioxide reduction activity

2019 Fall National Meeting

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