Exceptional alkaline-resistant Prussian blue analogue via montmorillonite protection for cesium (I) removal from...

The structural instability of ferrocyanides in alkaline solutions, which leads to framework collapse and hazardous cyanide release, has long constrained the broader application of Prussian Blue (PB) and its analogues (PBAs) in environmental and energy applications. Herein, we propose a montmorillonite (Mt)-stabilization strategy to mitigate pH-induced structural degradation in PBAs. Structural integrity of transition-metal (TM)-based PBAs (TM-PBAs, TM = Cu, Co, Ni, CuCo, CuNi, CoNi) was evaluated through free cyanide (FCN) release measurements. This strategy significantly inhibits FCN generation below WHO/EPA thresholds, especially Cu-PBA/MMt achieves 94.12 % FCN suppression at pH 12 with exceptional Cs⁺ uptake (181.57 mg/g), outperforming other TMs (CuCo > CuNi > Co > CoNi > Ni). These enhancements stem from Cu-PBA's crystallographic advantages, including minimized unit cell, maximized surface area, and optimized mesoporosity. Synergistic cation-exchange and lattice-entrapment mechanisms govern Cs⁺ adsorption, with CN^- ligands modulating K⁺ binding affinity. DFT calculations reveal Cu-PBA's minimal (C + N) Bader charge (-0.477 |e|) facilitates K⁺ release for efficient Cs⁺ uptake. Our stabilization strategy prevents PB/PBA framework collapse and cyanide leakage, maintaining performance in harsh conditions for environmental and energy applications.