Electronic, Optical and Charge Transport Properties of Zn-Porphyrin-C60 Mofs: A Combined Periodic and Cluster Modeling

Density functional theory (DFT) calculations were performed on the 5,15 meso-positions of nine porphyrin-containing MOFs; Zn<inf>2</inf>(TCPB)-(NMe<inf>2</inf>-ZnP); (H<inf>4</inf>TCPB = 1,2,4,5-tetrakis(4-carboxyphenyl)benzene), (NMe<inf>2</inf>-ZnP = [5,15-bis[(4-pyridyl)-ethynyl]-10,20-bis-(dimethylamine) porphinato]zinc(ii)) functionalized with nitrogen-, oxygen-, and sulfur-containing groups to study their effects on the electronic, optical and transport properties of the materials. The properties of these materials have also been investigated by encapsulating fullerene (C<inf>60</inf>) in their pores (C<inf>60</inf>@MOFs). The results indicate that the guest C<inf>60</inf> in the MOF generates high photoconductivity through efficient porphyrin/fullerene donor-acceptor (D-A) interactions, which are facilitated by oxygen and sulfur functionalities. DFT calculations show that C<inf>60</inf> interacts favorably in MOFs due to negative E<inf>int</inf> values. Encapsulated C<inf>60</inf> molecules modify the electronic band structure, affecting the conduction band and unoccupied states of MOFs corresponding to C<inf>60</inf> p orbitals. TD-DFT calculations show that incorporating C<inf>60</inf> promotes D-A interactions in MOFs, leading to charge transfer in the near-infrared and visible photoinduced electron transfer (PET) from porphyrins to C<inf>60</inf>. Nonequilibrium Green s function-based calculations for MOFs with sulfur group, with and without C<inf>60</inf>, performed using molecular junctions with Au(111)-based electrodes show increased charge transport for the doped MOF. These insights into tuning electronic/optical properties and controlling charge transfer can aid in the design of new visible/near-infrared MOF-based optoelectronic devices. © 2024 The Royal Society of Chemistry.