Structural Assembly from Phosphate to Germanophosphate by Applying Germanate as a Binder

Structural assembly from phosphate to germanophosphate by applying germanate as a binder has been achieved. Two isotypic porous compounds, K3[MII4(HPO4)2]­[Ge2O­(OH)­(PO4)4]·xH2O (MII = Fe, Cd; x = 2 for Fe and 3 for Cd, denoted as KFeGePO-1 and KCdGePO-1, respectively), contain a known transition-metal phosphate (TMPO) layer, ∞2{[M2(HPO4)3]2–}, which is built from chains of trans-edge-sharing MO6 octahedra bridged by MO5 trigonal bipyramids that were further linked and decorated by phosphate tetrahedra. The layers are bound by infinite chains of GeO5(OH) octahedra, resulting in a 3D open-framework structure with 1D 12-ring channels that are occupied by K+ ions and water molecules. The curvature of the TMPO layers and shape of the 12-ring windows can be tuned by the transition metals because of their Jahn–Teller effect.