Nanocages: Metal-Organic Polyhedra (MOPs) to Form M/MO Embedded Carbon Polyhedra

Metal-organic polyhedra (MOPs) are discrete and intrinsically porous molecular self-assemblies. MOPs exhibit rich surface chemistry; the existence of peripheral reactive sites is exploited by post-synthetic covalent and/or coordination-based polymeric structures by maintaining MOP identities. By further treatment, the dimensions of cuboctahedral MOPs are manipulated in an unprecedented manner into next-generation metal/metal oxides-doped carbon polyhedron nanocages/nanospheres. Herein, the predesigned mixed metal and metal oxides dopped carbon nanopolyhedral spheres/cages (M/MO@CNS) are obtained through the pyrolysis of MOPs. These composites are characterized by FTIR, Raman, PXRD, BET, ICP, XPS, FE-SEM, and TEM techniques. The spherical morphology of the nanomaterial is preserved as carbon spheres doped with metal-based nanoparticles (Cu⁰Co⁰/Cu₂OCoO@CNS), demonstrating excellent electrocatalytic performance. Compared to commercial iridium oxide, the carbon nanospheres incorporating metals/metal oxides presented a high activity profile for alkaline water oxidation. Catalysts prepared at 600°C and 1000°C revealed maximum current densities, as compared to the commercial IrO₂ benchmark catalyst. The current densities of 10 mA/cm² recorded low overpotentials/η₁₀ and Tafel slopes than IrO_2, with lower charge transfer resistance. Combined post-catalysis analyses and DFT calculations demonstrate that the synergistic interaction within Cu₂O/CoO@CNS optimizes the electronic structure and promotes electron transfer. It also balances the free energies of key intermediates and reduces the energy barrier of the OER rate-determining step, resulting in enhanced catalytic performance. The MOPs derived next-generation carbon-nanocages are tested for catalytic stability via chronopotentiometry, which shows that these composites remained stable during several hours of electrolysis.