Hierarchical-pore UiO-66-NH₂ xerogel with turned mesopore size for highly efficient organic pollutants removal

Persistent organic pollutants in water are not only a potential threat to human health, but also cause damage to the ecological environment. Hence, the removal of large organic pollutants from wastewater is of great importance for environmental protection. Herein, hierarchical-pore UiO-66-NH₂ xerogels (H-UiO-66-NH₂ xerogels) with different mesopore size, H-UiO-66-NH₂-11.6 nm and H-UiO-66-NH₂-3.7 nm, were successfully synthesized by combining sol-gel-based method and acid modulator, featuring the characteristics of simple operation, rapid and scalable process, low cost, and the high space-time yield (STY). N₂ adsorption-desorption isotherms reveal that the obtained H-UiO-66-NH₂ xerogels possess high surface area, hierarchical-pore structures, large pore volume, and turntable mesopore size. Batch adsorption experiments demonstrate that H-UiO-66-NH₂-11.6 nm has excellent adsorption performance for reactive red 195 (RR 195) dye removal. The maximum adsorption capacity of H-UiO-66-NH₂-11.6 nm is 884.96 mg g^-1, which is 4.7 times of the microporous UiO-66-NH₂ (185.15 mg g^-1). Moreover, the removal efficiency of H-UiO-66-NH₂-11.6 nm for RR 195 can exceed 99 %. The adsorption mechanism reveals that the excellent RR 195 capture stems from the large mesoporous structure and abundant adsorption sites provided by the Zr cluster and -NH₂ groups in H-UiO-66-NH₂-11.6 nm. Besides, H-UiO-66-NH₂-11.6 nm also exhibits a much larger adsorption capacity for some other organic pollutants, such as tetracycline, reactive black 5, and amoxicillin, demonstrating that the H-UiO-66-NH₂ xerogel has great potential for organic pollutant removal.