A　series　of　(Bi　2-δ　Y　δ　)Sn　2　O　7　solid　solutions　were　prepared　by　a　one-step　hydrothermal　method　to　investigate　the　correlation　between　the　electronic　structures　and　photocatalytic　activity.　All　the　(Bi　2-δ　Y　δ　)Sn　2　O　7　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　(Bi　2-δ　Y　δ　)Sn　2　O　7　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　Y　3+　induces　the　shrinkage　of　the　lattice　of　(Bi　2-δ　Y　δ　)Sn　2　O　7　solid　solutions.　Consequently,　the　contribution　of　Bi　6s　orbitals　to　electronic　structures　of　(Bi　2-δ　Y　δ　)Sn　2　O　7　solid　solutions　can　be　continuously　tuned　by　Y　3+　substitution　for　Bi　3+　.　Density　function　theory　calculations　reveal　that　the　Bi　6s　and　O　2p　states　dominate　the　top　of　valence　band　of　Bi　2　Sn　2　O　7　,　while　the　bottom　of　conduction　band　mainly　consists　of　the　states　of　Sn　5s,　O　2p　and　Bi　6p.　Once　the　Bi　3+　ions　are　substituted　by　Y　3+　,　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　Bi　2　Sn　2　O　7　.　Moreover,　the　band　dispersions　of　valence　band　and　conduction　band　become　narrower　after　Y　3+　introduction　into　the　lattice　of　(Bi　2-δ　Y　δ　)Sn　2　O　7　solid　solutions.　As　a　result,　the　photocatalytic　performance　for　decomposition　of　2-naphthol　has　been　suppressed　by　the　Y　3+　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.