A Magnetic Route to Measure the Average Oxidation State of Mixed-Valent Manganese in Manganese Oxide Octahedral Molecular Sieves (OMS)

摘要

Porous manganese oxide octahedral molecular sieves (OMS) have drawn significant research interest due to their applications in catalysis,ion storage and separation,battery electrodes,chemical sensors,and patterning.In addition to the various nanoscale tunnel structures,one very important feature that makes manganese oxide OMS a unique group of functional materials is the mixed-valent framework manganese (Mn),usually 3~+ and 4~+ or 2~+,3~+,and 4~+.The importance of mixed-valent Mn is also demonstrated by the enhanced ferromagnetism and colossal magneto-resistance effects in the La_(1-x)A_xMnO_3 (A = Ca,Ba,or Sr) perovskite systems and Mn-doped semiconductors,such as GaAs and ZnO for spintronics (spin-carrier electronics),where mixed-valent Mn plays an important role as the hole carrier.The ratio of different valent Mn in OMS is usually characterized by the average oxidation state (AOS) of Mn.