The new high-pressure borate Co7B24O42(OH)2·2 H2O-Formation of edge-sharing BO4 tetrahedra in a hydrated borate

► High-pressure/high-temperature synthesis of the new borate hydrate Co7B24O42(OH)2·2 H2O. ► In the structure of Co7B24O42(OH)2·2 H2O, two B2O6 units are connected to “vierer” rings. ► Pressure favours the formation of edge-sharing BO4 tetrahedra in the chemistry of borates.