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

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 m² g^-1. Furthermore, this approach is successfully scaled to 100 g quantities, and the resulting scale-up MOF shows strong potential for practical CO₂ adsorption applications.