A new inorganic–organic hybrid solid, Cd(phen)(H 2 PO 4 ) 2 ⋅H 2 O (phen=1,10-phenanthroline), has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, FTIR, elemental analysis, ICP analysis, powder X-ray diffraction and fluorescent spectrum. The compound crystallizes in the triclinic system, space group P-1 (No. 2), a=6.8027(3) Å, b=11.0806(4) Å, c=12.1725(5) Å, α=63.8120(10)°, β=81.043(2)°, γ=86.935(2)°, V=813.19(6) Å3, Z=2. The structure is built from strictly alternating CdO 4 N 2 octahedra and H 2 PO 4 tetrahedra through their vertices, forming an infinite ladder-like architecture. This compound shows intense photoluminescence upon photoexcitation at 358 nm.