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 scantling 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 91.1 mg g(-1) was achieved at room temperature over 24 h when 5 mg of UiO-66-P was immersed in 40 mL of a 500 mg L-1 MB solution. This capacity is much higher than that of UiO-66 (24.5 mg g(-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. (C) 2017 Elsevier Inc. All rights reserved.