Carbonization of cobalt complexes is a simple but versatile technique to prepare magnetic cobalt/carbon nanocomposites (MCoCNs) as heterogeneous catalysts for solution-based reactions. However, most of MCoCNs consist of sheet-like carbon matrices with sparse cobalt nanoparticles (Co NPs), making them exhibit low catalytic activities, porosity and magnetism. In this study, 2,6-Pyridinedicarboxylic acid (PDA) is selected to prepare a 3-D cobalt coordination polymer (CoPDA). MCoCN derived from CoPDA consists of a porous carbon matrix embedded with highly-dense Co NPs. This magnetic Co NP-embedded carbon nanocomposite (MCo@C) appears as a promising catalyst for energy generation and biomass conversion. As H-2 generation from NaBH4 is selected as a model reaction for energy generation, MCo@C rapidly catalyzes hydrolysis of NaBH4 to generate H-2 center dot E-a obtained by MCo@C is also much lower than many noble metallic and cobalt-based catalysts. MCo@C also exhibits a stable and efficient catalytic activity for catalyzing hydrolysis of NaBH4 for multiple-cycle H-2 production. In addition, MCo@C can be also used to catalyze conversion of the lignin model compound, vanillyl alcohol (VAL), to vanillin (VN) using H2O2 and air as oxidants. The selectivities for VN can be up to 99% and 100% using H2O2 and air as oxidants, respectively. MCo@C can be also re-used to catalyze VAL conversion to VN without significant loss of catalytic activity. These results indicate that MCo@C is a conveniently prepared and highly effective and stable magnetic cobalt/carbon nanocomposite for versatile catalytic applications. The preparation scheme here can be also applied to fabricate other carbon-supported metallic catalysts.