Highly mesoporous metal–organic framework assembled in a switchable solvent

The mesoporous metal–organic frameworks are a family of materials that have pore sizes ranging from 2 to 50 nm, which have shown promising applications in catalysis, adsorption, chemical sensing and so on. The preparation of mesoporous metal–organic frameworks usually needs the supramolecular or cooperative template strategy. Here we report the template-free assembly of mesoporous metal–organic frameworks by using CO(2)-expanded liquids as switchable solvents. The mesocellular metal–organic frameworks with large mesopores (13–23 nm) are formed, and their porosity properties can be easily adjusted by controlling CO(2) pressure. Moreover, the use of CO(2) can accelerate the reaction for metal–organic framework formation from metal salt and organic linker due to the viscosity-lowering effect of CO(2), and the product can be recovered through CO(2) extraction. The as-synthesized mesocellular metal–organic frameworks are highly active in catalysing the aerobic oxidation of benzylic alcohols under mild temperature at atmospheric pressure.