N-Doped Carbon Interior-Modified Mesoporous Silica-Confined Nickel Nanoclusters for Stereoselective Hydrogenation

Hydrodearomatization attracts extensive interest for removing polycyclic aromatic hydrocarbons in diesel but still suffers from sluggish efficiency due to the vulnerable sulfur resistance of noble metal catalysts and inferior hydrogenation performance of traditional transition-metal catalysts. Herein, we propose a low-temperature in situ carbonization of the template strategy for constructing N-doped carbon interior-modified MCM-41 (NC@MCM)-confined ultra-dispersed Ni nanocluster catalysts (Ni/NC@MCM). The optimal hydrogenation catalyst Ni/NC300@MCM with ultrafine Ni nanoclusters (2.4 nm) exhibits 100% naphthalene conversion and 100% decalin selectivity at 100 °C and atmospheric pressure. Additionally, trans-decalin stereoselectivity up to 95% is achieved compared with other catalysts. The N-doped carbon inside mesochannels not only plays a critical role in stabilizing and dispersing Ni species but also promotes H2 adsorption/activation and enriches naphthalene molecules. Theoretical results reveal that the pyridinic-N and pyrrolic-N species can boost the adsorption of naphthalene. The dual confinement of active sites and reactants in this microenvironment makes the outstanding trans-decalin stereoselectivity a reality. Moreover, Ni/NC300@MCM shows distinguished activities in selective hydrogenation of dibenzothiophene and quinoline, and the applicability of the template carbonization method on HMS and MCM-48 is confirmed. This work opens a unique avenue in promising metal nanocluster catalysts for stereoselective hydrogenation.