[C4N2H12]2[In3(HPO4)5(H2PO4)F2]: The first 2-D fluorinated indium phosphate with double-sheet layers and 8-ring channels

A new structure type of layered fluorinated indium phosphate with In/P ratio of 1/2, [C4N2H12]2[In3(HPO4)5(H2PO4)F2] (1), has been hydrothermally synthesized in the presence of piperazine as the structure directing agent. Its structure is built up from In-centered octahedra (InO4F2 and InO5F) and P-centered tetrahedra (PO3(OH), PO2(OH)(double bond; length as m-dashO) and PO(OH)2(double bond; length as m-dashO)), forming the unique double-sheet inorganic layers with 8-ring channels along the [0 1 0] directions.