Activation and Zr precursor influence on UiO-66-NH2 composites for efficient cationic and anionic dye removal

• The ZrCl 4 precursor yielded a higher surface area and micropores. • The ZrOCl 2 ·8H 2 O precursor achieved 60% crystallinity and 60% mesopores. • Activation processes enhanced adsorption capacity and improved dye removal efficiency. • Maximum adsorption capacities were 263.1 mg/g for methylene blue (MB) and 277.77 mg/g for Congo red (CR). • The activated composites retained over 96 % MB adsorption efficiency after four cycles. This study investigates the synthesis of UiO-66-NH 2 @HTC composites, focusing on the control of surface charge, textural properties, and crystallinity. Surface charge modification was achieved through activation processes to enhance affinity for specific pollutants. By utilizing ZrCl 4 and ZrOCl 2 ⋅8H 2 O precursors, the textural properties were optimized, leading to higher mesopore content and improved crystallinity with the ZrOCl 2 ⋅8H 2 O precursor. The UiO-66-NH 2 (ZrCl 4 )@HTC composite exhibited a crystallinity of 51.7 %, with 40 % mesopores and 57 % micropores, while the UiO-66-NH 2 (ZrOCl 2 )@HTC composite showed a crystallinity of 60 %, consisting of 60 % mesopores and 37 % micropores. Adsorption followed the Langmuir isotherm model, with maximum adsorption capacities of 263.1 mg/g for methylene blue (MB) and 277.77 mg/g for Congo red (CR), driven by hydrogen bonding and electrostatic interactions. The activated UiO-66-NH 2 @HTC composites demonstrated remarkable reusability. These findings emphasize the significant role of surface charge modification, pore structure optimization, and crystallinity enhancement in developing high-performance adsorbents.