Frameworks formed of low dimensional chains can be prepared by combining metals and bidentate organic linkers that favour one-directional growth (Fig. ). The electrical conductivity of 1D MOFs, such as Ni(II) with 1,2,4,5-benzenetetramine ligand or Cu(II) with 1,5-diamino-4,8-dihydroxy-9,10-anthraceneedione ligand, originates from the conjugated π-d system. While an intrinsic pore structure is absent, mesopores can be formed from the voids between particles. A large family of two-dimensional MOFs has now also been established (Fig. ). Electrically conductive 2D MOFs, such as Ni3(HITP)2, feature high inplane conjugation. They achieve high conductivity based on the conjugated π-d system as well as through π-π stacking. The stacking structure generates unidirectional pore channels in the bulk material that are accessible to gases and liquids. In contrast, 3D MOFs have interconnected building units along three spatial dimensions such as the prototype MOF-5 built from Zn4O clusters bridged by 1,4-benzodicarboxylate with an interconnected pore structure. Some families of electrically conductive 3D MOFs have now also been reported, and their exploration remains an active area of research.