Breaking Phase-Selectivity Barriers: Scalable Room-Temperature Synthesis and Catalytic Properties of Functionalized...

The pursuit of sustainable and scalable synthesis for metal-organic frameworks (MOFs) is crucial for their industrial application, yet achieving phase purity under room temperature remains a significant challenge, particularly for kinetically metastable phases like MIL-101(Fe). In this work, we developed a room-temperature synthesis strategy that enables gram-scale production (∼50 g/batch) of phase-pure MIL-101(Fe) with solvent recyclability. The use of pyridine as a phase-directing agent within a ternary solvent system (dioxane/pyridine/H2O) kinetically favors the formation of MIL-101(Fe) over the thermodynamic products MIL-53 or MIL-88B. Furthermore, we established substituent-dependent synthesis rules by systematically investigating steric effects on solvent selection, where MIL-101(Fe) with small substituents was synthesized using the original dioxane/pyridine/H2O mixtures, and MIL-101(Fe) with bulky/multiple substituents required N,N-dimethylformamide (DMF)/N,N-dimethylacetamide (DMA) to achieve phase-pure products. The functionalized MIL-101(Fe) derivatives were evaluated as heterogeneous catalysts for solvent-free diindolylmethane synthesis. This work establishes a framework linking substituent identity, synthetic conditions, and catalytic performance in functionalized MIL-101(Fe) materials.