Gas-liquid-solid three-phase catalysis is a key process in the global chemical industry.[1] One of the main challenges associated with this system is that the mass transfer of gas reactants often limits the reaction rates. This is because most non-polar gases (e.g. H2 and O2) are poorly soluble in conventional solvents under atmospheric pressure.[2] Therefore, costly engineering solutions are often necessary to increase the solubility or accelerate the mass diffusion rate of gases.
An innovative solution to this challenge is to disperse a bespoke porous material such as metal–organic frameworks (MOFs) in conventional solvents. These permanently porous particles can act as nanosized gas shuttles to efficiently transport gas from the gas–liquid interface to catalyst surfaces.[3] Our group recently pioneered this field by using a phase partitioned MOF particle featuring a hydrophobic core that can remain dry in water, and a hydrophilic shell that will ensure the stability of this colloidal dispersion. We demonstrated that a mere 2 vol% addition of such porous additive in water can dramatically accelerate H2 mass transfer during the hydrogenation of hydroxymethylfurfural (HMF) due to a shuttling effect, leading to a 350% increase of HMF conversion.[3]
Further advancing this research requires a better method for the quantification of the mass transfer rate of gases in catalytic systems. This work aims to develop a general method to investigate the rate of mass transfer in the three-phase systems and compare the structure-property relationships of different MOF materials as gas shuttles.