Electrically Conductive 3D Metal–Organic Framework Featuring π‑Acidic Hexaazatriphenylene Hexacarbonitrile Ligands with Anion−π Interaction and Efficient Charge-Transport Capabilities

Semiconducting metal–organic
frameworks (MOFs) show great potential to foster myriad advanced electronics
and energy technologies, but they must possess adequate charge-carrier
concentration and efficient charge-transport pathways in order to
display useful electrical conductivity. A new intrinsically conducting
3D framework [Ag2(HATHCN)­(CF3SO3)2]n was constructed by employing
a highly π-acidic 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile
(HATHCN) ligand, which assumed a paramagnetic HATHCN•– radical anion character by acquiring electron density from the TfO– anions involved in the anion−π interaction
and facilitated charge movement along the staircase-like [−Ag+–HATHCN−]∞ chains having ample
Ag4d+–N2p orbital overlap
in the valence band region. As a result, the MOF displayed a narrow
band gap (1.35 eV) and promising electrical conductivity (7.3 ×
10–4 S/cm, 293 K) that ranked very high among those
recorded for 3D MOFs. This work presents a new strategy to construct
intrinsically conductive 3D frameworks by exploiting the dual metal
coordination and anion−π interaction capabilities of
a highly π-acidic HATHCN ligand.