MOF-structured metal@carbon core/shell hybrids for efficient Joule heating catalysis

Active sites, where chemical reactions occur, are central to catalysis, energy storage, and environmental remediation. Porous metal-organic frameworks (MOFs) offer exceptionally high surface areas; however, their metal ions are strongly coordinated to organic linkers, which limits their chemical and physical activity, and their frameworks typically collapse during high-temperature treatment. In this study, copper (Cu)- and nickel (Ni)-based MOFs are converted into carbonized MOFs (C-MOFs), denoted C-MOF/Cu and C-MOF/Ni, respectively, through a one-step heat treatment that preserves the octahedral MOF morphology. The C-MOFs are composed of metal nanoparticles encapsulated by graphitic carbon (metal@carbon core/shell), which, in C-MOF/Cu, are further bridged by amorphous carbon. Molecular dynamics (MD) simulations, coupled with experimental temperature-programmed carbonization, elucidate the structural evolution from MOFs to C-MOFs. Owing to the electrical resistivity of the carbon shell, these materials can be employed in Joule heating catalysis, which enables ammonia decomposition over C-MOF/Ni at much lower temperatures than conventional thermal catalysis. The C-MOF/Ni also exhibits significantly higher activity than Ni-impregnated carbon, which is attributed to its larger number of accessible active sites and internal porous structure.