Construction of low-vacancy hexagonal Prussian blue analogues for efficient rubidium recovery

Abstract

Prussian blue analogues (PBAs) are considered a promising adsorbent for rubidium recovery due to their high ion exchange capacity and selectivity. However, the development of PBAs-based rubidium adsorbents with excellent stability and adsorption capacity is still hindered by the inevitable CN ligand vacancies. Herein, a synthetic strategy is proposed to slow down crystal nucleation and promote the self-repair of crystal defects by incorporating N-doped porous carbon (NPC) as a solid modifier during the synthesis process. As a result, the vacancy content of Zn-PBA-NPC is significantly decreased and large size twinned crystals are produced, which remarkably improves the thermal and acid-base stability. Benefiting from the high content of K⁺ in the low-vacancy Zn-PBA-NPC, it achieves a high adsorption amount of 199.1 mg/g and rapid adsorption kinetics of just 5 min for Rb⁺. In addition, it shows good selectivity in the presence of other alkali metal ions. This work not only prepares a high-performance adsorbent for efficient recovery of Rb⁺, but also facilitates insights into the design and construction of low-vacancy PBAs.