An acentric borate family, Ag₄B₄O₇X₂ (X = Br, I), has been prepared by slow cooling stoichiometric melts in evacuated silica ampules. Their crystal structure is comprised of two porous interpenetrating frameworks and demonstrates a further development of the "salt-inclusion" architecture toward a "covalent-inclusion" structure. The (Ag₂X)⁺ sublattice shows strong anharmonic vibrations. Thermal expansion is strongly anisotropic because of the presence of condensed rigid kernite boron-oxygen chains aligned perpendicular to the c axes.