Amine-functionalized Zr-MOF/CNTs nanocomposite as an efficient and reusable photocatalyst for removing organic contaminants

In the current study, a new water-stable nanocomposite and amine-functionalized zirconium-based metal-organic framework/carbon nanotube (UiO-66-NH₂@CNT) was synthesized using the hydrothermal approach, displaying superior photodegradation of anionic and cationic dyes under visible-light irradiation. Methyl orange (MO) and Rhodamin B (RhB) were used as organic contaminant models. The prepared materials were fully characterized by FTIR, XRD, SEM, TEM, BET, TGA, UV–Vis absorption, and ICP analysis. The optimal nanocomposite, UiO-66-NH₂@CNT(3 wt%) exhibited the highest degradation efficiency of RhB (100%) and MO (93%) in less than 30 min under optimum conditions in comparison with other prepared materials (F-CNT, UiO-66, Ui-66-NH₂, and other UiO-66-NH₂@CNT-X samples). Different effective parameters such as initial dye concentration, catalyst dosage, and solution pH have been also studied. The possible mechanism for photodegradation of dyes over UiO-66-NH₂@CNT(3 wt%) showed that the increase in the photocatalytic activity can be attributed to the range of improved visible-light absorption (lower band gap), and the great specific surface area based on composite and water stability as well as the formation of an effective hetero-junction. Trapping studies also revealed that hydroxyl radicals (OH^•) and photo-generated holes (h⁺) had the most influence on the photocatalytic degradation of both dyes. The kinetic study for the dye degradation process was fitted with a first-order kinetic model. Also, after six-reuse cycles, the optimum composite still showed high photodegradation ability (>90%).