Theoretical design of metal-porphin systems for selective interaction with trace geosmin

Geosmin, even at minuscule concentrations, can significantly compromise the taste and odor of drinking water, making its removal a critical challenge. In this study, an integrated computational strategy encompassing DFT, QTAIM, NCI analysis, RDG, DOS, and Molecular Dynamics simulations was used to probe how geosmin interacts with both pristine Porphin and its copper-coordinated variant. The findings clearly show that copper coordination markedly enhances geosmin adsorption. Specifically, the average isosteric heat increases from 18.66 to 20.67 kcal/mol, while the energy distribution narrows, suggesting more consistent interaction strength. Mulliken charge and electrostatic potential analyses indicate a partial charge transfer involving the hydroxyl group of geosmin, supporting the conclusion that van der Waals and hydrogen-bonding interactions play a significant role. Additionally, copper coordination dramatically reduces the HOMO-LUMO gap from 0.0756 eV to 0.00083 eV signaling increased electronic reactivity and a shift towards semi-metallic character. Molecular Dynamics simulations confirm that these frameworks are both structurally and thermally stable, with total energy fluctuations remaining within ±0.17 kcal/mol. Altogether, these results highlight copper-modified Porphin as a highly promising platform for geosmin adsorption, offering robust thermal stability, enhanced selectivity, and notable electronic property modulation. Such frameworks are potential candidates for next-generation VOC sensors and advanced water purification technologies.