First-principles investigation of aspirin, paracetamol, and ibuprofen adsorption on triquinoxalinylene and benzoquinone-based covalent organic framework.

Pharmaceutical contaminants such as aspirin (ASP), paracetamol (PAR), and ibuprofen (IBU) present increasing risks to environmental and human health, necessitating efficient detection and removal strategies. In this study, we performed a comprehensive first-principles investigation of their adsorption on a triquinoxalinylene and benzoquinone-based covalent organic framework (TQBQ-COF). The geometries were optimized and the adsorption complexes were characterized using density functional theory. The results reveal that all three drug molecules are effectively accommodated within the electron-rich central cavity of the COF, forming stable host-guest assemblies through van der Waals interactions while preserving the structural integrity of the framework. Frontier molecular orbital and global reactivity analyses indicate that drug adsorption, particularly for IBU, significantly reduces the HOMO-LUMO gap and chemical hardness, enhancing electronic sensitivity, reactivity, and charge-transfer capability. Electron density difference and non-covalent interaction analyses confirm directional electron flow from the drugs to the COF and identify stabilizing interactions governing adsorption. Simulated UV-Vis spectra show pronounced red-shifts upon drug adsorption, with the IBU@TQBQ-COF complex exhibiting the largest effect. Thermodynamic analyses further confirm spontaneous, exothermic adsorption dominated by enthalpy contributions. Collectively, these findings highlight TQBQ-COF as a highly sensitive and robust platform for drug detection and removal in aqueous and biologically relevant environments.