Adsorptive removal of pharmaceutical pollutants by defective metal organic framework UiO-66: Insight into the contribution of defects.

The development of defective structure in MOFs can offer a novel approach to tailor the properties of MOFs-type adsorbent for better adsorption performance. In this study, the contribution of defective structure in UiO-66 to the adsorptive removal of pharmaceutical pollutants from aqueous solution was investigated. The results showed that the controlled defects in UiO-66 greatly affected adsorption equilibrium time, adsorption capacity and adsorption selectivity. Slightly defected UiO-66 contained more open frameworks, and it exhibited faster adsorption equilibrium. However, a high degree of destruction to the amorphous state resulted in a longer equilibrium time, due to the interference in the diffusion process as the result of severe structural collapse and interpenetration. Moreover, a higher degree of structural damage of UiO-66 led to a higher adsorption capacity because of the increased active sites. The maximum adsorption capacity was 321 mg/g for the as-prepared defective UiO-66, which was much higher than that of perfective UiO-66 (54.5 mg/g). Furthermore, defective UiO-66 had a higher adsorption affinity for diclofenac sodium than other studied pharmaceutical pollutants. This study could provide insight into the relationship between defective property and adsorption performance. The results will deepen the understanding of the adsorption mechanism of MOFs-type adsorbents, and help the design of MOFs-type adsorbents with fast adsorption equilibrium, higher adsorption capacity and adsorption selectivity.