Cationic Metal–Organic Framework Nanoparticles Based on UiO-66 for Effective ReO₄^– Capture

ReO4– as a hazardous waste severely threatens environmental safety and human health. The high-efficiency adsorbent for the removal of ReO4– is of immense interest but still faces challenges. Herein, we established cationic metal–organic framework nanoparticles by an amino protonation strategy. Based on a facile and green method, we first introduced dense amino groups (6.59 mmol/g) in UiO-66 in situ to prepare UiO-66-(NH2)2, during which acetic acid as a modulator was applied to construct defects. Subsequently, UiO-66-(NH2)2 was acidified to the cationic UiO-66-(NH3+Cl–)2. Notably, this cationic adsorbent exhibits a high adsorption capacity of 590.2 mg g–1 and a short adsorption equilibrium time of 240 min for ReO4–. Besides, the excellent chemical stability and reusability endow UiO-66-(NH3+Cl–)2 with promising potential in practical applications. Experimental characterization and density functional theory (DFT) calculations suggest that the electrostatic interaction, ion exchange, and coordination interaction jointly contribute to the effective removal of ReO4–. Thus, this work provides a highly efficient cationic metal–organic framework nanoparticle for ReO4– removal and, importantly, proposes a feasible strategy for constructing cationic adsorbents.