Aqueous-phase DFT insights into ciprofloxacin adsorption on COOHfunctionalized carbon nanotubes: energetics, electronic structure, and sesign principles

Context Pharmaceutical residues such as ciprofloxacin (CIP) are increasingly recognized as persistent aquatic contaminants with adverse ecological impacts. Understanding their interactions with functionalized nanomaterials is essential for designing efficient adsorbents. Here, we explore the adsorption mechanism of CIP on carboxyl-functionalized carbon nanotubes (CNT?COOH) under aqueous conditions. The study reveals favorable binding energetics, significant stabilization through solvation effects, and electronic structure changes that highlight CNT?COOH as an effective platform for pharmaceutical pollutant removal. Methods All calculations were carried out using density functional theory (DFT). Geometry optimizations, harmonic vibrational frequency analyses, and solvation modeling were performed within the polarizable continuum model (PCM, water). Electronic structure calculations were conducted with B3LYP, M06-2X, and ?B97X-D functionals in combination with the 6-311++G(d,p) basis set. The Gaussian 09W package was employed for all computations, and GaussView 6 was used for molecular visualization and analysis.