A　series　of　(Bi2-δYδ)Sn2O7　solid　solutions　were　prepared　by　a　one-step　hydrothermal　method　to　investigate　the　correlation　between　the　electronic　structures　and　photocatalytic　activity.　All　the　(Bi2-δYδ)Sn2O7　samples　were　characterized　by　X-ray　diffraction,　transmission　electron　microscopy,　infrared　and　UV-vis　absorption　spectroscopy,　and　the　Brunauer-Emmett-Teller　technique.　The　effects　of　Bi　6s　orbitals　in　(Bi2-δYδ)Sn2O7　solid　solutions　on　the　electronic　structures　and　photogradation　of　colorless　2-naphthol　solution　were　investigated　experimentally　and　theoretically.　It　is　found　that　the　introduction　of　Y3+　induces　the　shrinkage　of　the　lattice　of　(Bi2-δYδ)Sn2O7　solid　solutions.　Consequently,　the　contribution　of　Bi　6s　orbitals　to　electronic　structures　of　(Bi2-δYδ)Sn2O7　solid　solutions　can　be　continuously　tuned　by　Y3+　substitution　for　Bi3+.　Density　function　theory　calculations　reveal　that　the　Bi　6s　and　O　2p　states　dominate　the　top　of　valence　band　of　Bi2Sn2O7,　while　the　bottom　of　conduction　band　mainly　consists　of　the　states　of　Sn　5s,　O　2p　and　Bi　6p.　Once　the　Bi3+　ions　are　substituted　by　Y3+,　the　intensity　of　Bi　6s　states　is　weakening　at　the　top　of　valence　band　while　the　bottom　of　conduction　band　retains　the　same　feature　observed　for　pure　Bi2Sn2O7.　Moreover,　the　band　dispersions　of　valence　band　and　conduction　band　become　narrower　after　Y3+　introduction　into　the　lattice　of　(Bi2-δYδ)Sn2O7　solid　solutions.　As　a　result,　the　photocatalytic　performance　for　decomposition　of　2-naphthol　has　been　suppressed　by　the　Y3+　substitution,　since　the　electronic　structure　limits　the　mobility　of　the　photoinduced　charge　carriers.　Our　results　suggest　that　high　photocatalytic　activity　of　Bi-containing　compounds　should　originate　from　the　good　band　dispersions　of　valence　band　and　conduction　band　involving　the　Bi　6s　orbitals.　©　2015　Elsevier　B.V.　All　rights　reserved.