Exploring the capabilities of metal-doped phthalocyanine (MPC, M = Co, Cu, Fe, Ni, Zn) for adsorption of CO2: A DFT study.

Phthalocyanine-based covalent organic frameworks (PC-COFs) are a novel subclass of COFs that integrate phthalocyanine units to enhance electronic, optical, and catalytic properties. These frameworks are particularly effective in CO2 adsorption due to their high surface area, tunable porosity, and exceptional stability. In this study, we have employed density functional theory (DFT) calculations to explore the electronic properties of phthalocyanine doped with various metal centers (Co, Cu, Fe, Ni, Zn) and their impact on CO2 adsorption. The geometries of metal-doped phthalocyanines and their CO2 complexes were optimized using the B3PW91 functional with the LANL2DZ basis set. Adsorption energies, electronic structures, and reactivity indices such as HOMO-LUMO gaps, ionization potentials, and electron affinities were analyzed. The findings revealed that Fe-doped phthalocyanines exhibited the highest reactivity and strongest CO2 adsorption due to favorable charge transfer interactions. Additionally, aromaticity indices (HOMA and Bird) indicated enhanced aromatic character upon CO2 adsorption. These insights provide a foundation for designing more efficient PC-COF materials for CO2 capture, emphasizing the crucial role of electronic properties and metal center selection in optimizing adsorption performance.