Rational Low‐Temperature Synthesis of Ultrasmall Nanocrystalline Manganese Binary Oxide Catalysts under Controlled Metal Cation Hydration in Organic Media

Abstract Ultrasmall nanocrystalline manganese binary oxides with various compositions and crystal structures were synthesized by a convenient, rational low‐temperature method. These oxides were obtained in 2‐propanol‐based solutions using the organic‐solvent‐soluble MnO₄⁻ as a manganese source under controlled metal cation template hydration. Three‐dimensional spinel oxides were generated selectively by suppressing the hydration of metal cation templates. One‐dimensional tunnels and two‐dimensional layered structures predominated under adequate and high hydration, respectively. These oxides acted as efficient reusable heterogeneous catalysts for primary alcohol ammoxidation and amidation using aqueous NH₃ as a nitrogen source and O₂ (air) as a terminal oxidant. In particular, ultrasmall Co−Mn spinel oxide effectively catalyzed the ammoxidation of primary alcohols into their corresponding nitriles. The Li−Mn spinel oxide promoted the hydration of ammoxidation‐derived nitriles, facilitating the one‐pot conversion of primary alcohols into primary amides.