Proposed Modification of the Graphene Analogue Ni3(HITP)2 To Yield a Semiconducting Material

The metal–organic framework material Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 (Ni3(HITP)2) is composed of layers of extended conjugated planes analogous to graphene. We carried out density functional theory (DFT) calculations to model the electronic structure of monolayer, bilayer, and bulk Ni3(HITP)2. These materials have intriguing electronic properties; for example, appreciable band dispersion is predicted not only in-plane but also perpendicular to the stacking planes. This suggests that, unlike graphene, the material may have appreciable conductivity in all crystallographic directions. Moreover, the bulk and bilayer structures are predicted to be metallic; in contrast, a 2D monolayer of the material exhibits a band gap. Insight obtained from studies of the transition of the material from semiconducting to metallic as the dimensionality increases from 2D to 3D suggests the possibility of producing a 3D semiconducting material by inserting spacer moieties between the layers. Our calculations suggest that it is not energetically favorable for Ni3(HITP)2 to accept a spacer linker (i.e., pyridine); however, changing the coordinating metal to Cr makes spacer insertion energetically favorable. The proposed 3D material is predicted to possess a band gap of ∼1 eV with electron/hole effective masses similar to that of silicon.