Green and Scalable Synthesis of Metal–Organic Framework via a Two‐Stage Crystallization Approach

Abstract Green synthesis of metal–organic framework (MOF) is urgently demanded to enable scalable manufacturing and practical applications. However, the current one‐step approaches typically require prolonged energy input or involvement of organic‐solvent conditions for MOF crystallization. Herein, a two‐stage crystallization approach is reported that yields high‐quality MOF in water with just 5 min of energy input. In the first stage, nucleation is triggered mechanochemically, where 5 min of water‐assisted milling generates a critical partially ordered intermediate. In the second stage, crystal growth proceeds solely via an in situ standing process under ambient conditions, during which the intermediate spontaneously transforms and grows into a crystalline framework, as observed by in situ characterization. Moreover, the aqueous ambient conditions promote thermodynamically controlled crystal growth, thereby yielding MOF with uniform morphology, high crystallinity, and a surface area of up to 1376 m ² g ⁻¹ . Furthermore, this approach is successfully scaled to 100 g quantities, and the resulting scale‐up MOF shows strong potential for practical CO ₂ adsorption applications.