Rhombohedral　chromia　with　three-dimensionally　(3D)　ordered　mesopore　structures　were　fabricated　adopting　the　ultrasound-assisted　nanocasting　strategy　with　3D　ordered　mesoporous　silica　(KIT-6)　as　hard　template　and　chromium　nitrate　as　metal　source.　The　physicochemical　properties　of　the　materials　were　characterized　by　the　XRD,　TGA/DSC,　BET,　TEM/SAED,　XPS,　and　H-2-TPR　techniques,　and　their　catalytic　activities　were　evaluated　for　the　oxidation　of　typical　volatile　organic　compounds　(VOCs),　such　as　formaldehyde,　acetone,　and　methanol.　It　is　found　that　there　were　tri-,　penta-,　and　hexavalent　chromium　ions　in　the　3D　mesoporous　structure.　Compared　to　the　bulk　chromia,　the　mesoporous　chromia　materials　were　larger　in　surface　area　(69-124　m(2)/g)　and　could　be　reduced　at　lower　temperatures.　Among　the　chromia　catalysts.　the　meso-Cr-400　one　obtained　after　calcination　at　400　degrees　C　showed　the　best　performance.　Over　meso-Cr-400　at　space　velocity　=　30,000　mL/(gh),　formaldehyde,　acetone,　and　methanol　conversions　achieved　90%　at　117,　124.　and　130　degrees　C,　respectively;　the　corresponding　apparent　activation　energies　were　45.6,　49.7,　and　50.8　kJ/mol.　It　is　concluded　that　the　ultrasound　treatment　was　a　key　step　to　improve　the　mesoporosity　quality　of　the　chromia　materials　during　the　nanocasting　process,　and　the　factors,　such　as　low-temperature　reducibility,　3D　ordered　mesoporous　architecture,　and　high-surface　area,　were　responsible　for　the　excellent　catalytic　performance　of　meso-Cr-400.　(C)　2010　Elsevier　B.V.　All　rights　reserved.