Coordination and space confined preparation of nickel sub-nanoparticles within a metal-organic framework for catalytic degradation of methyl orange

Nickel sub-nanoparticles were prepared by coordination-space confinement strategy within a metal-organic framework. [Display omitted] •Highly dispersed Ni sub-nanoparticles with the size around 1∼2 nm were derived from the MOF of UiO-67-NN.•The UiO-67-NN support has a coordination-confinement effect on the Ni(NO3)2 precursor.•The resulting nickel sub-nanoparticles are space-confined within the UiO-67-NN structure.•Ni@UiO-67-NN-P composite serves as an efficient catalyst for the degradation of methyl orange dye. Nickel nanoparticles are a kind of promising heterogeneous catalysts. However, highly dispersed Ni sub-nano particles (SNPs) encapsulated in carbon composites are rarely reported due to their tendency to aggregate and the lack of strong interactions between Ni2+ precursors and carbon materials. In this work, we present a facile coordination-space confinement strategy to prepare Ni SNPs@carbon composites by using a metal organic framework of UiO-67-NN as support. Utilizing the coordination interaction between Ni2+ ions and 2,2′-bipyridine-5,5′-dicarboxylate (NN-bpdc) ligands from the supports, the impregnated Ni2+ ions were stoichiometrically fixed and then in-situ transferred into NiO SNPs in the first pyrolysis process. Owing the space-confinement of UiO-67-NN, these NiO SNPs were then in-situ reduced into Ni SNPs with the size around 1∼2 nm, which were uniformly dispersed in the carbon composite derived from UiO-67-NN. Detailed studies revealed that the coordination-space confinement also played a vital role in the in-situ pyrolysis process of Ni2+→ NiO → Ni0. The degradation percentage of methyl orange dye in the presence of Ni@UiO-67-NN-P composite was higher than those reference catalysts prepared in conditions without either coordination or space confinement. The present work provides a potential strategy for the preparation of metallic SNPs catalysts with high efficiency.