Electrocatalytic synthesis of methylamine from nitrate and carbon dioxide on a heterometallic polyphthalocyanine

Abstract

Electrocatalytic coreduction of nitrate and CO₂ provides an opportunity for the synthesis of organonitrogen chemicals. The major challenge is to realize the simultaneous reduction of nitrate and CO₂ into active intermediates for C–N bond formation. In this work, methylamine is synthesized from nitrate and CO₂ on a polyphthalocyanine electrocatalyst with heterometal centers (Co₂Cu₁PPc). Notably, it is found that the Co and Cu centers coordinated with the conjugated macrocyclic network of polyphthalocyanine can catalyze CO₂ reduction to formaldehyde and nitrate reduction to hydroxylamine, respectively. The nucleophilic attack of hydroxylamine on formaldehyde generates a formaldoxime intermediate, which is then further reduced to methylamine. The overreduction reactions of hydroxylamine and formaldehyde intermediates are suppressed by Co₂Cu₁PPc. This bifunctional catalyst with heteronuclear active centers simultaneously catalyzes nitrate and CO₂ reduction to key intermediates for C–N bond formation.