Ligand decorated nickel-based nanoparticles supported onto MXenes in catalytic hydrogenation of N-heterocycles

Abstract

The development of efficient first-row transition metal catalysts is essential for advancing sustainable chemical processes. In this study, we report the synthesis of nickel-based nanoparticles (NiNPs) functionalized with N-heterocyclic carbene ligands and immobilized onto Ti₃C₂ MXene. Our convergent synthetic approach enables comprehensive and straightforward characterization of each component within the final hybrid material. The NiNPs are obtained through chemical reduction of a well-defined nickel organometallic complex, resulting in the formation of small nickel metal nanoparticles (3.0 ± 0.8 nm) that are rapidly oxidized to the corresponding NiO and Ni(OH)₂ based nanoparticles containing surface NHC ligands. The hybrid catalyst exhibits high activity and selectivity in the hydrogenation of N-heterocycles under hydrogenation conditions, achieving quantitative yields at low catalyst loadings, particularly notable for a nickel-based system. Recycling studies revealed progressive catalyst deactivation, primarily due to sintering of NiNPs, which reduces the number of active surface sites. However, the catalytic activity can be fully restored through a mild regeneration treatment under reducing conditions. These findings underscore the potential of NiNP/MXene-based materials for selective hydrogenation reactions, and highlight the importance of addressing key challenges in sustainability such as the use of non-noble metals, catalyst stability and recyclability. Further design modifications aimed at preventing nanoparticle sintering may enhance the long-term viability of these systems in catalytic hydrogenation processes.