Electronic, optical and charge transport properties of Zn-porphyrin-C 60 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 2 (TCPB)-(NMe 2 -ZnP); (H 4 TCPB = 1,2,4,5-tetrakis(4-carboxyphenyl)benzene), (NMe 2 -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 60 ) in their pores (C 60 @MOFs). The results indicate that the guest C 60 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 60 interacts favorably in MOFs due to negative E int values. Encapsulated C 60 molecules modify the electronic band structure, affecting the conduction band and unoccupied states of MOFs corresponding to C 60 p orbitals. TD-DFT calculations show that incorporating C 60 promotes D-A interactions in MOFs, leading to charge transfer in the near-infrared and visible photoinduced electron transfer (PET) from porphyrins to C 60 . Nonequilibrium Green's function-based calculations for MOFs with sulfur group, with and without C 60 , 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.