Nanoarchitectonics of Porous Carbons Templated by Inorganic Metal Oxides and Alkali Metal Salts for Energy and Environmental Applications

Inorganic nanoparticles are widely used as sacrificial templates for the synthesis of porous carbons due to their good thermal stability, characteristic shapes, tunable sizes, compatibility with carbon precursors, and lower cost and toxicity than conventional silica-based templates. Their use not only ensures the development of hierarchical porosity but also the creation of short-range graphitic domains in the carbon matrix. These qualities make porous carbons suitable for different applications, including adsorption, separation, catalysis, and energy storage and conversion. Within the series of inorganic nanoparticle templates, metal oxides such as MgO, ZnO, Fe₂O₃, Fe₃O₄, and MnO₂, and alkali metal salts such as NaCl and KCl stand tall as templates. They are thermally and structurally stable, do not react with the carbon precursor, and do not require high-cost, harsh removal methods such as HF washing. This review provides up-to-date discussions of metal oxides (MgO, ZnO, Fe₂O₃, Fe₃O₄, and MnO₂) and metal salts (NaCl, KCl, and composite salts) to produce porous carbons and addresses other aspects of their structures. This is a focused review that critically analyzes the recently published literature and will serve as a guiding framework for the future design and development of porous carbons.