Selective　epoxidation　of　propylene　by　molecular　oxygen　under　mild　conditions　remains　a　great　challenge　to　date.　Here,　we　successfully　designed　and　constructed　molybdenum　oxide　in　an　electron-rich　state　by　introducing　the　transition　metal　copper　into　MoO　3　–Bi　2　SiO　5　/SiO　2　through　a　simple　co-impregnation　method.　The　new　Mo　species　has　the　structure　Mo　6−δ　O　3−　x　,　and　greatly　improved　propylene　epoxidation　performance　at　low　temperatures.　Propylene　oxide　formation　rate　increased　from　106　to　336　g　PO　kg　cat　−1　h　−1　.　X-ray　photoelectron　spectrometry　(XPS)　and　UV–visible　diffuse　reflection　(UV–vis　DRS)　characterizations　suggest　that　the　bridging　oxygen　bond　between　molybdenum　and　copper　produces　an　oxygen　vacancy,　which　facilitates　the　formation　of　the　electron-rich　state　of　molybdenum　with　lower　3d　electronic　binding　energy.　In　addition,　the　incorporation　of　Cu　effectively　inhibits　the　formation　of　Bi　2　Mo　3　O　12　and　improves　the　dispersion　of　Mo　species.　Furthermore,　kinetic　studies　show　that　Cu-modified　catalysts　maintain　lower　apparent　activation　energy　for　propylene　epoxidation,　which　obviously　reduced　the　selectivity　of　acrolein　and　then　conspicuously　improved　the　selectivity　of　propylene　oxide.　Our　results　not　only　offer　a　new　solution　for　low　temperature　propylene　epoxidation,　but　also　provide　a　new　strategy　for　the　design　of　other　types　of　low-temperature　epoxidation　catalysts.　©　2018　Elsevier　Inc.