Ultrasmall Nickel Nanoparticles on a Covalent Triazine Framework for Ammonia Borane Hydrolysis and Transfer Hydrogenation of Nitroaromatics.

Ammonia borane (AB) is a promising candidate as a hydrogen reservoir in terms of both dihydrogen storage and hydrogen source for transfer hydrogenation (TH) to unsaturated organic substrates. Ultrasmall Ni nanoparticles (NPs) have been synthesized by metal vapor synthesis (MVS) and supported on a selected covalent triazine framework (CTF^Ph). The physical and chemical properties of the Ni/CTF^Ph nanocomposite have been thoroughly investigated. Despite the high Ni loading (10 wt %), the material exhibits well-dispersed ultrasmall Ni nanoparticles (2.2 nm), unveiling the non-innocent role of the N-doped templating carrier toward NPs dispersion and stabilization. The Ni/CTF^Ph has shown excellent catalytic performance in the AB hydrolysis and AB transfer hydrogenation (AB-TH) for the conversion of a variety of nitroarenes, including halogen-substituted ones, into the corresponding anilines. As for the latter process, Ni/CTF^Ph has unveiled a remarkable catalytic efficiency, durability, and reusability under both batch and continuous-flow operative conditions. Noteworthily, whatever the catalytic process at work, Ni/CTF^Ph certainly ranks or even outperforms most Ni-based systems of the state-of-the-art, including its Ni/VXC analogue (Ni 10 wt % prepared by MVS technique) synthesized using a plain and undoped carbon support (i.e., Vulcan XC-72R). [ABSTRACT FROM AUTHOR]