Methylene blue adsorption in DUT-5: Relatively strong host-guest interactions elucidated by FTIR, solid-state NMR, and XPS

The existence of dyes in water causes environmental and health problems. Thus, a Metal-Organic Framework entitled DUT-5 was explored in the methylene blue adsorption process. DUT-5 showed a high adsorption performance exhibiting a maximum adsorption capacity of 140.66 mg g⁻¹ in a short contact time of 45 min and stability at different pHs from 4 to 8. The adsorption isotherms and kinetic data followed the Temkin and PSO models, respectively, which suggested the involvement of physico-chemical forces in the adsorption process. The thermodynamic study confirmed the exothermic nature of the process. The key to the high adsorption of MB was the relatively strong host-guest interactions by cooperative and different physicochemical interactions, which were elucidated by FTIR, solid-state NMR, and XPS. Moreover, DUT-5 proved to be an exceptional candidate for methylene blue remediation with remarkable chemical stability and cyclability.