CO2-mediated direct N-formylation of nitro compounds by a metal–organic framework node-supported cobalt(ii) catalyst

Abstract

The one-pot reductive N-formylation of nitro substrates using CO₂ as a renewable C1 feedstock is a sustainable and practical route to access formamides, key intermediates in pharmaceuticals and bioactive molecules. We report an efficient strategy for the reductive N-formylation of nitro compounds with CO₂ and phenylsilane enabled by a single-site cobalt(II) hydride catalyst immobilized within a zirconium-based UiO-67 metal–organic framework. The confined environment of UiO-67 facilitates tandem nitro group reduction and CO₂ incorporation within a single catalytic platform, delivering formamides in excellent yields. The catalytic system displays a broad substrate scope, tolerating aromatic and aliphatic nitro compounds bearing electron-donating, electron-withdrawing, halogen and heteroaromatic substituents. UiO-67-CoH demonstrates good stability and recyclability, retaining its crystalline framework while achieving nearly 99% conversion of nitro substrates and delivering up to 94% yield of the corresponding formamides. Detailed mechanistic insights obtained from control experiments, spectroscopic analysis, kinetic studies and DFT calculations reveal the role of the MOF in stabilizing reactive cobalt hydride species and suppressing deactivation pathways. Overall, this study establishes UiO-67-CoH as a robust and versatile platform for CO₂ valorization and underscores the broader potential of MOFs in designing earth-abundant single-site catalysts for sustainable transformations to produce value-added fine chemicals.