NH₄[BGe₃O₈]:  A New Borogermanate Framework Made of Infinite-Chain Building Blocks

A new microporous borogermanate NH₄[BGe₃O₈] has been synthesized by a molten boric acid flux method with “reagent” quantities of water in which GeO₂, ethylenediamine, H₂O, and H₃BO₃ (5:8:14:25) were heated together at 513 K for 4 days. The structure consists of {Ge₆O₁₈}_n chains, further linked together via BO₄ tetrahedra, forming a three-dimensional open framework with intersecting channel systems including one-dimensional 10-membered-ring (MR) channels. Interestingly, the infinite chains {Ge₆O₁₈}_n as building blocks, built of alternating 4- and 6-MRs made of vertex-sharing GeO₄ tetrahedra, construct the borogermanate framework. It is noteworthy that the high viscosity of the reactive medium and the quantity of water play important roles in the formation of the compound.