Dual-Functional Ice/Water Interface Allows High-Yield Formation of Al₁₃ with Low Energy

Keggin Al₁₃[(AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺ is a well-known efficient coagulant widely used in water purification and treatment. The production of high-content Al₁₃ is still costly, and it is therefore essential to develop new eco-efficient and low energy demand synthesis methods for practical application. Solid–water interfaces play a dominant role in heterogeneous reactions, which can be utilized in various processes through rationally designed interfaces. Here, we designed an Al³⁺ and OH^– interface by using NaOH-doped ice as a solid and AlCl₃ solution as liquid for Al₁₃ production. This system provides a natural and renewable solid–water interface through ice melting, while simultaneously minimizing external energy input and maintaining an effective heterogeneous interface reaction for production of high-quality Al₁₃ species. The dual-function of ice/water interface enables the formation of Al₁₃ with a high yield of up to 90% compared to initial total Al. Moreover, global areas with cold winter climate conditions may exploit this process reducing the need for external artificial energy. As AlCl₃ can be obtained with low cost, this method may have great potential for industrial mass production of Al₁₃.