A mechanochemical synthetic strategy of isoreticular flexible metal-organic frameworks with pre-designed mixed metal clusters

Mechanochemistry has emerged as a sustainable alternative to traditional solvothermal methods for synthesizing metal-organic frameworks (MOFs), offering reduced solvent usage, shorter reaction times, and scalability. However, the synthesis of flexible MOFs, such as the MIL-88 series, remains challenging due to the difficulty in forming secondary building units (SBUs) under mechanochemical conditions. Herein, we present a novel strategy for the mechanochemical synthesis of the MIL-88 series using pre-assembled mixed-metal clusters as precursors. This approach effectively overcomes limitations in controlling metal ratios and suppressing undesired phase mixtures, enabling the efficient and rapid formation of MIL-88 frameworks under mild conditions. The synthesized MIL-88s, including mixed-metal variants, were comprehensively characterized to confirm phase purity, structural fidelity, and tunable metal compositions. This strategy not only facilitates access to flexible MOFs that were previously difficult to synthesize mechanochemically but also demonstrates the feasibility of precisely controlling metal ratios in mixed-metal systems. These advancements underscore the significant potential of this approach for further expanding the scope and applications of mechanochemical synthesis.