Nitrate Upcycling Mediated by Organonickel Catalysis

Abstract

Nitrogen oxides (NOx) are major environmental pollutants and to neutralize this long‐term environmental threat, new catalytic methods are needed. Although there are biological denitrification processes involving four different enzymatic reactions to convert nitrate (NO3–) to dinitrogen (N2), it is unfortunately difficult to apply in industry due to the complexity of the processes. In particular, nitrate is difficult to functionalize because of its chemical stability. Thus, there is no organometallic catalysis to convert nitrate to useful chemicals. In this article, we present that a nickel pincer complex is effective as a bifunctional catalyst to stepwise deoxygenate NO3– by carbonylation and further to C–N coupling. By using this nickel catalysis, nitrate salts can be selectively transformed into various oximes (>20 substrates) with excellent conversion (>90%). Here, we demonstrate for the first time that the highly inert nitrate ion can be functionalized to produce useful chemicals by a new organonickel catalysis. Our results show that the NOx conversion and utilization (NCU) technology is a successful pathway for environmental restoration coupled with value‐added chemical generation.