The fabrication of ultrafine noble metal nanoparticle (NMNP)-based catalysts is significant for heterogeneous catalysis due to their excellent performance for organic transformations. In this study, N-doped micro-mesoporous hollow carbon nanospheres (HCN) with a nitrogen content of similar to 3.5 wt% are easily prepared by simple carbonization. Then, ultrafine Pd NPs are immobilized on HCN, affording Pd/HCN as a dual-function catalyst which exhibits superior catalytic activity for the selective oxidation of 5-hydroxymethylfurfural (HMF) and hydrogenation of nitroarenes, under mild reaction conditions. The doping of HCN with nitrogen is beneficial for the high dispersion, anchoring, and particle size control of ultrafine Pd NPs, leading to the maximum utilization of Pd atoms and further enhancing the catalytic activity of Pd/HCN. In addition, the obtained Pd/HCN catalyst exhibits excellent reusability and stability. Hence, this study demonstrates the prospect of developing ultrafine NMNP-supported catalysts with high performance for organic transformations. (C) 2019 Elsevier Inc. All rights reserved.