A new open-framework tin(II) sulfate, formulated as C 4 H 12 N 2 •Sn(SO 4 ) 2 •H 2 O, was prepared under the structuredirecting effect of piperazine. This compound features a 3D structure with 16-ring channels. Under ultraviolet light irradiation, it emits bright yellow luminescence with a near-unity photoluminescence quantum yield. Theoretical calculations were carried out to understand the luminescence mechanism.