A facile approach to fabricate an immobilized-phosphate zirconium-based metal-organic framework composite (UiO-66-P) and its activity in the adsorption and separation of organic dyes

A novel immobilized-phosphate zirconium-based metal-organic framework composite, denoted as UiO-66-P, was synthesized by a solvothermal method using UiO-66 nanoparticles and Na₃PO₄ ligands. The products were characterized by powder X-ray diffraction, energy dispersive spectrometry, field emission scanning electron microscopy, thermogravimetric analysis, infrared spectroscopy, zeta potential analysis, and gas adsorption measurements. The UiO-66-P nanocrystals, which comprised negatively charged frameworks, exhibited high stability, excellent porosity, and efficient charge-selective capture and separation of the cationic dye Methylene Blue (MB). An uptake capacity of 91.1mgg^-1 was achieved at room temperature over 24h when 5mg of UiO-66-P was immersed in 40mL of a 500mgL^-1MB solution. This capacity is much higher than that of UiO-66 (24.5mgg^-1). The adsorption capability of UiO-66-P for MB was improved by 272% compared to that of pristine UiO-66. The effects of variables such as initial pH, MB concentration, and contact time were investigated. In addition, the as-obtained UiO-66 nanocrystals exhibited excellent adsorption capability for the anionic dyes Congo Red, Acid Chrome Blue K, and Methyl Orange.