High-Precision Multistage Molecular Dynamics Simulations and Quantum Mechanics Investigation of Adsorption Mechanisms of Cerium-Based H3BTC MOF (Ce-H3BTC-MOF) on Pristine and Functionalized Carbon Nanotubes

Metal-organic frameworks (MOFs) and carbon nanotubes (CNTs) exhibit exceptional physicochemical properties, making them promising candidates for nanotherapeutics, catalysis, and drug delivery. However, CNTs face inherent limitations in solubility and functionalization, which hinder their practical applications. This study systematically investigates the adsorption mechanisms of cerium-based benzene-1,3,5-tricarboxylate MOFs (Ce-H₃BTC-MOF) on pristine (PCNT), mildly functionalized (MFCNT), and densely functionalized (DFCNT) CNTs using multistage molecular dynamics simulations and quantum mechanics calculations. Functionalization was achieved by grafting 5 (-COOH) groups on the MFCNT and 20 (-COOH) groups on the DFCNT, enhancing interfacial interactions. Loading configurations of 1-5 Ce-H₃BTC MOF molecules were analyzed to understand binding stability and molecular dispersion. Simulation results demonstrated enhanced adsorption on functionalized CNTs due to π-π stacking and electrostatic interactions, with 5CeBTC-1DFCNT exhibiting the highest cohesive energy (311.01 kcal/mol) and optimized solubility (1.13 MPa^1/2). Density functional theory calculations revealed a HOMO-LUMO energy gap of 0.21029 eV for BTC and 0.23089 eV for CeO₂, indicating electronic stability. Root mean square deviation (rmsd) and radius of gyration (R_g) analyses confirmed structural stability, with 1CeBTC-1MFCNT maintaining the lowest rmsd (∼2.47 Å) and 5CeBTC-1DFCNT exhibiting significant fluctuations (∼6.87 Å) due to steric hindrance. This study advances the understanding of CNT-MOF hybrid systems by elucidating their interfacial dynamics, providing a foundation for future applications in nanomedicine and catalysis.