Lawrence Berkeley National Laboratory

The material demands for metal-organic frameworks (MOFs) for next-generation energy-efficient CO2 capture technologies necessitate advances in their expedient and scalable synthesis. Toward that end, the recently discovered expanded MOF-74, or M2(dobpdc), where M = divalent metal cation and dobpdc = 4,4′-dioxido-3,3′-biphenyldicarboxylate, can now be prepared in minutes via a controlled dissolution-crystallization route from divalent metal oxides as precursors. We show that the available surface area of the metal oxide plays a critical role in the precursor dissolution, which was found to be rate-limiting. Based on this understanding of the reaction trajectory, we pushed the chemical transformation to its fringe kinetic limit by configuring the metal oxide precursors as ligand-free colloidal metal oxide nanocrystals, which allowed MOF formation in less than 1 min. MOFs prepared by this strategy were highly crystalline, with BET surface areas on par with conventional multihour syntheses from metal halide salts. This method was also applied successfully in the synthesis of M2(dobdc) MOFs, highlighting its generality. Our work challenges the conventional wisdom that plurality of steps in MOF formation is inherently time-intensive.