A　new　sodium　cesium　strontium　borate,　Na2Cs2Sr(B9O15)(2),　has　been　synthesized　and　its　crystal　structure　determined　by　single-crystal　XRD　methods.　The　compound　crystallizes　in　the　space　group　P2(1)/c　(No.　14)　with　the　following　cell　parameters:　a　=　8.4670(17)　angstrom,　b　=　8.5220(17)　angstrom,　c　=　17.206(3)　angstrom,　beta　=　92.60(3)degrees,　V　=　1240.2(4)　angstrom(3),　Z　=　2.　It　represents　a　new　structure　type　in　which　three　[B3O7](5-)　triborate　groups　are　bridged　by　two　common　oxygen　atoms　to　form　a　[B9O19](11-)　group　that　is　further　condensed　into　a　3D　(3)(infinity)[B9O15](3-)　network,　with　the　shorthand　notation　9:infinity(3)[3　x　(3:2　Delta　+　T)],　where　D　and　T　represent　BO3　triangles　and　BO4　tetrahedra,　respectively.　The　3D　borate　anionic　network　also　affords　intersecting　open　channels　as　well　as　pockets　that　accommodate　Cs+,　Sr2+,　and　Na+　cations.　IR　spectrum　further　confirms　that　this　compound　contains　low　symmetric　BO3　and　BO4　groups.　UV-VIS　diffuse　reflectance　spectrum　shows　a　high　degree　of　transparency　under　the　visible　light　and　a　band　gap　of　about　3.26　eV.　Solid-state　fluorescence　spectrum　demonstrates　a　broad　emission　band　at　around　494.8　nm.　Band　structure　calculations　by　the　density　functional　theory　method　indicate　that　it　is　an　indirect　band-gap　insulator.　(C)　2014　Elsevier　B.V.　All　rights　reserved.