Highly Porous, Electrically Conductive Two-Dimensional Nickel-Hexaaminodehydrobenzoannulene Frameworks

Electrically conductive two-dimensional metal-organic frameworks (2D c-MOFs) represent a new frontier in porous crystalline materials, where both charge-carrier transport and mass diffusion are critical to function. However, reconciling high porosity with electrical conductivity remains a major challenge in developing this class of compounds. To address this challenge, we investigate two new 2D c-MOFs featuring hexaamino derivatives of dehydrobenzoannulenes (DBAs)─hexaaminodehydrobenzo[12]annulene (HA12) and hexaamino-dehydrobenzo[18]annulene (HA18) with a C₃-symmetry axis─as organic ligands. These shape-persistent, fully π-conjugated macrocycles can be viewed as core-expanded analogues of hexaaminotriphenylene (HATP), a prototypical ligand for 2D c-MOFs. Their reactions with nickel ions yield highly porous Ni₃(HI12)₂ and Ni₃(HI18)₂. Notably, Ni₃(HI18)₂ exhibits a Brunauer-Emmett-Teller surface area of 1520 m² g^-1, among the highest reported for 2D c-MOFs. Furthermore, both MOFs show electrical conductivities comparable to that of the HATP-based counterpart, Ni₃(HITP)₂, as supported by density functional theory calculations. On the other hand, they differ significantly in electronic properties such as band gap and ionization energy, reflecting variations in their ligand structures. The DBA-based MOFs also demonstrate enhanced chemiresistive sensitivity compared to Ni₃(HITP)₂. Overall, this work presents a ligand design strategy that achieves high porosity while preserving electrical conductivity and at the same time enables diversification of electronic and sensing characteristics of 2D c-MOFs.