Porous manganese oxides possess a wealth of different
structures. Among them are the octahedral molecular sieves
(OMS) which are crystalline mixed-valent manganese oxides with
a defined microporous tunnel structure consisting of egde- and
corner-shared [MnO6]-octahedra [1,2]. The diameters of the tunnel
cross sections are in the range of that typical for zeolite pores. In
the case of K-OMS-2 (cryptomelane structure) with the chemical
composition KMn8O16, for instance, the square-shaped tunnels
have a size of 0.46 nm 0.46 nm