Tailored SO2 capture in multivariate UiO-66(Zr) MOFs: Experimental insights and theoretical mechanisms

Sulfur dioxide (SO 2 ) emissions present significant environmental and health risks, yet efficiently capturing SO 2 remains challenging due to its corrosive nature and the limited performance of conventional adsorbents. In this study, we developed multivariate metal-organic frameworks (MTV-MOFs) based on UiO-66(Zr) for effective SO 2 capture. Through systematic ligand functionalization with -OH, -NH 2 , -SO 3 H, and -(NH 2 ) 2 groups on terephthalic acid linker, we developed a series of MTV-UiO-66 materials with tailored pore environments and adsorption characteristics. UiO-66-NH 2 exhibited superior performance with an SO 2 uptake of 252.9 mL g −1 at 298 K and 1 bar. Ideal adsorbed solution theory (IAST) calculations demonstrated improved selectivity for SO 2 over N 2 (847) and CO 2 (31), surpassing that of the parent UiO-66. Dynamic breakthrough experiments further confirmed the practical viability of MTV-UiO-66 materials for SO 2 capture under both dry and humid (50 % RH) conditions, with UiO-66-NH 2 retaining a capacity of 30.73 mL g −1 in dry settings and exhibiting robust performance in moisture-rich environments. Grand Canonical Monte Carlo (GCMC) simulations and density functional theory (DFT) calculations provided molecular-level insights into the adsorption mechanisms, revealing that functional groups play a crucial role in modulating binding interactions through hydrogen bonding, dipole-dipole interactions, and spatial confinement effects. The computational binding energies corroborated the experimental isosteric heats of adsorption, validating the integrated experimental-computational approach.