A twofold interpenetrating network constructed from silver ions coordinated to fumaric acid and pyrazine: Ag2(fum)(H2fum)(pyz)2 (fum = fumarate, pyz = pyrazine)

► A layer structure containing silver ions coordinated by fumarate anions and fumaric acid prepared by hydrothermal synthesis. ► The layers are cross-linked by pyrazine. ► The structure is twofold interpenetrated.