Towards developing efficient metalloporphyrin-based hybrid photocatalysts for CO2 reduction; an ab initio study

Abstract

A series of thiophene-based donor–acceptor–donor (D–A–D) oligomer substituted metalloporphyrins (MPors) with different 3d central metal-ions (M = Co, Ni, Cu, and Zn) were systematically investigated to screen efficient hybrid photocatalysts for CO₂ reduction based on density functional theory (DFT) and time-dependent DFT simulations. Compared with base MPors, the newly designed hybrid photocatalysts have a lower bandgap energy, stronger and broader absorption spectra, and enhanced intermolecular charge transfer, exciton lifetime, and light-harvesting efficiency. Then, the introduction of D–A–D electron donor (ED) groups into the meso-positions of MPors is a promising method for the construction of efficient photocatalysts. According to the calculated adsorption distance, adsorption energy, Hirshfeld charge and electrostatic potential analysis, it was revealed that CO₂ physically adsorbed on the designed photocatalyst surface. In addition, among the studied model systems the ZnPor(ED)₄ catalyst with four D–A–D electron donors exhibits the best photocatalytic performance due to its broadest absorption spectra with λ_max = 500.12 nm and the highest adsorption energy of about 26 kJ mol⁻¹. Finally, the sensing ability of the ZnPor(ED)₄-based multi-terminal molecular junction for CO₂ gas detection is determined using Green's functions. The transmission plots of this molecular junction are barely changed due to the physical adsorption of CO₂ on the molecular surface, leading to the low sensitivity of the device. We believe that such a theoretical design can provide a general approach for further experimental and computational studies of photocatalysts used in the CO₂ reduction process.