N-Formylation of amines utilizing CO2 by a heterogeneous metal–organic framework supported single-site cobalt catalyst

Abstract

Catalytic N-formylation of amines using CO₂ is considered pivotal for the sustainable synthesis of formamides, key chemical feedstocks for synthesizing heterocycles, pharmaceuticals and bioactive molecules. We report a single-site cobalt(II) hydride catalyst supported on an aluminum metal–organic framework (DUT-5-CoH), which is an active heterogeneous catalyst for transforming both primary and secondary amines, as well as anilines, into the corresponding N-formamides utilizing CO₂ and either H₂ or phenylsilane as a reducing agent. DUT-5-CoH is tolerant to a range of amine substrates bearing various functional groups under 10 bar CO₂. Various aromatic and aliphatic primary amines as well as secondary amines were readily converted to the corresponding N-formamides in excellent yields and selectivity. The MOF could be recycled and reused up to 15 times without decreasing the catalytic activity in the N-formylation of p-methoxybenzylamine. The kinetic, spectroscopic and density functional theory calculation studies suggest that the reaction of DUT-5-CoH and CO₂ forms cobalt-formate, which undergoes PhSiH₃ assisted formamide formation with benzylamine in the turnover limiting step. This work highlights the development of robust single-site earth-abundant metal catalysts based on metal–organic frameworks for efficient and chemoselective N-formylation of amines using CO₂.