Synthesis of porous CrOx pillared octahedral layered manganese oxide materials

Chromium oxide pillared manganese oxide materials were prepared by intercalating layered manganese oxide with chromium hydroxyl acetate clusters under reflux condition. The as-synthesized materials were heated at 209 degrees C in flowing nitrogen for Ih to result in chromium oxide pillared manganese oxides. X-ray diffraction, UV-vis, FTIR, BET surface area and pore size distribution, temperature programmed desorption, elemental analysis, and X-ray absorption spectrometry were used to study the intercalating process and the structures of the pillared materials. Porous materials with a high specific surface area and a narrow pore size distribution (18 Angstrom) were obtained. The removal of bound water and dehydroxylated water was responsible for the production of high surface area in the pillared material. The decomposition of acetate groups bidentate-linked to Cr starting at 200 degrees C in Na resulted in a concomitant decrease in porosity. Although the ordering of the layers was largely destroyed and the materials remained "amorphous" under XRD study, TEM morphology studies suggest that the material was still layered. EXAFS studies indicate the formation of Cr-O-Mn bonds in the resultant materials via corner-shared linkages of CrO6 and MnO6 octahedra.