Recent Manganese Oxide Octahedral Molecular Sieves (OMS-2) with Isomorphically Substituted Cationic Dopants and Their Catalytic Applications

The present report describes the structural and physical-chemical variations of the potassium manganese oxide mineral, alpha-MnO2, which is a specific manganese octahedral molecular sieve (OMS) named cryptomelane (K-OMS-2), with different transition metal cations. We will describe some frequently used synthesis methods to obtain isomorphic substituted materials [M]-K-OMS-2 by replacing the original manganese cationic species in a controlled way. It is important to note that one of the main effects of doping is related to electronic environmental changes, as well as to an increase of oxygen species mobility, which is ultimately related to the creation of new vacancies. Given the interest and the importance of these materials, here, we collect the most recent advances in [M]-K-OMS-2 oxides (M = Ag, Ce, Mo, V, Nb, W, In, Zr and Ru) that have appeared in the literature during the last ten years, leaving aside other metal-doped [M]-K-OMS-2 oxides that have already been treated in previous reviews. Besides showing the most important structural and physic-chemical features of these oxides, we will highlight their applications in the field of degradation of pollutants, fine chemistry and electrocatalysis, and will suggest potential alternative applications.

Automated summary

This report discusses the structural and physical-chemical variations of the potassium manganese oxide mineral with different transition metal cations, as well as the synthesis of isomorphic substituted materials. Doping effects are primarily related to changes in electronic environment and increased mobility of oxygen species, ultimately leading to new vacancies. The report also highlights the applications of these oxides in pollution degradation, fine chemistry, and electrocatalysis.