Abstract: A novel 3D anionic indium phosphate-phosphite, formulated as |(C₁₀H₁₀N₂)_1.5(H₃O)₃|In₁₈(H₂O)₁₂(HPO₄)₁₂(HPO₃)₁₆(H₂PO₃)₆(1).was hydrothermally prepared by using 4, 4′-bipyridine as a structure directing agent. Single-crystal X-ray diffraction analysis results showed that compound 1 crystallized in the hexagonal system space group P6_3/m(No.176) with unit cell parameters a = 1.378 43(19) nm, b = 1.378 43(19) nm, c = 2.805 8(6) nm, V = 4.617 0(13) nm³. Compound 1 exhibited a unique pillar-layer open-framework constructed from InO6 octahedra, HPO₃ pseudo-tetrahedra and HPO₄ tetrahedra, resulting extra-large 16-MRs channels. The guests molecular of 4, 4’-bipyridine were deposited in these channels. Host-guest assembly leaded to an enhanced fluorescence properties of compound 1