Potential of pyridine nanobelt in detecting and trapping of harmful UV filters

Sunscreens, a primary defense against ultraviolet (UV) radiation, use UV filters to mitigate the harmful effects of UVA and UVB radiation, including DNA damage, skin aging, and cancer. However, organic UV filters like benzophenones, oxybenzone, sulisobenzone, and PABA are persistent pollutants, posing environmental risks due to their incomplete removal by conventional wastewater treatment. This study investigates the encapsulation of hazardous UV filters inside a stable belt[14]pyridine nanobelt to facilitate their removal through host-guest interactions. The higher values of interaction energies (E_int) of the designed host-guest complexes ranging from - 13.70 to -26.11 kcal/mol, ensure the stability of the complexes. Frontier molecular orbital (FMO) analysis reveal the significant role of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the host nanobelt towards the HOMO and LUMO of complexes, which is confirmed via density of states (DOS) analysis. Natural bond orbital (NBO) analysis determines the direction of charge transfer, i.e., from the host towards guest species in all complexes. The highest magnitude of NBO charge is observed for sulisobenzone@belt complex, i.e., 0.022|e|. Electron density difference (EDD) analysis visually illustrate the accumulation of charge density over the guest in all the complexes, i.e., a validation of the direction of charge transfer predicted via NBO analysis. The results of non-covalent interaction index (NCI) and quantum theory of atoms in molecules (QTAIM) analyses reveal that the host-guest complexes are stabilized via van der Waals interactions, and a greater number of bond critical points (BCPs) are found for sulisobenzone@belt i.e., 15. Moreover, the recovery time decreases with increasing temperature and is highest for the complex with greater E_int i.e., 1.4[Formula: see text]10⁷ s (at 298 K) for oxybenzone@belt complex. Overall, the study aims to design stable host-guest complexes for effective encapsulation of harmful UV filters, in order to reduce their harmful effects.