Pronounced Catalytic Enhancement through Phase Partitioned Metal-Organic Framework Gas Shuttles

Three-phase catalytic processes, such as hydrogenation, play a vital role in the chemical industry. However, the low solubility of gases in conventional solvents often limits reaction rates due to poor mass transfer. To tackle this challenge, current approaches rely on high pressures, elevated temperatures, or specialized reactor designs─measures that significantly increase capital costs. Here we report the design of a phase partitioned metal-organic framework, U6P@U6, featuring a hydrophobic UiO-66 core that can remain porous in water, and a hydrophilic UiO-66 exterior that ensures colloidal stability. In a model hydrogenation reaction of hydroxymethylfurfural to 2,5-bis(hydroxymethyl)furan catalyzed by Pd-on-carbon, U6P@U6 functions as a permanently porous gas shuttle that can efficiently transport hydrogen from the gas-liquid interface to catalyst surfaces. We show that addition of only 3.7 wt % of U6P@U6 to the reaction mixture resulted in a 350% increase in HMF conversion due to accelerated H₂ mass transfer. This allows for six times the amount of Pd-on-carbon catalyst to be used in the reaction without mass transfer limitations. A mechanistic study reveals that the enhancement of mass transfer results from a 140-fold increase in the diffusion rate of H₂ into the porous particles at the gas-liquid interface compared with that into water.