Photoconductive metal-organic frameworks based on 10,20-meso-substituted Zn-porphyrin and fullerene C60

Abstract

Metal-organic frameworks (MOFs) with electrical conductivity have potential applications as electrochemical sensors, electrocatalysis, and energy storage. We present the design of a new class of conductive MOFs based on porphyrin, substituted in the 10,20 meso-positions (1 amine, 2 hydroxy, 3 methoxy, 4 nitro, and 5 dimethylamine). Furthermore, these MOFs are doped with fullerene molecules (C60) within their pores, resulting in 1@C60, 2@C60, 3@C60, 4@C60, and 5@C60. To study the electronic and optical properties of these MOFs before and after the incorporation of C60, theoretical calculations based on density functional theory (DFT) (PBE+D3/DZP) and time-dependent DFT (TPSSh/6-31G) were performed. Incorporating C60 causes a decrease in the bandgap of MOFs due to its unoccupied crystalline p orbitals (LUCOs). It also promotes the Q and Soret (B) bands of porphyrin in the MOF to absorb at longer wavelengths. Charge transport properties were calculated using the Keldysh nonequilibrium Green's function (NEGF) formalism and molecular junctions with Au(111)-based electrodes for 1 and 1@C60. When a bias voltage of 0.2 V is applied, an increase in current is obtained for 1@C60 concerning 1. Our results suggest that MOF@C60 is a promising alternative for designing new photoconductive materials because of the donor-acceptor interactions generated.