Metal–organic framework-based porous matrix membranes for improving mass transfer in forward osmosis membranes

Abstract

Internal concentration polarization (ICP) in substrate layer is one of the most critical bottlenecks of the forward osmosis (FO) process. In this study, we explored the use of metal–organic frameworks (MOFs) as a removable filler to prepare MOF-based porous matrix membranes (PMMs) for improving the mass transfer in the FO substrates and hence controlling the ICP. MOF-based porous matrix substrates (PMSs) with three different types of MOFs were prepared via phase inversion by adding MOF particles into the polyacrylonitrile (PAN) dope solution. A thin selective layer was prepared using a layer-by-layer (LbL) deposition method on top of the porous matrix FO substrate. The bond dissociation energy (BDE) between metal ions and organic linker of MOF particles played an important role for the selection of fillers of PMMs. For MOF particles with lower BDE (<~200kJ/mol), the corresponding MOF-based porous matrix FO membranes had higher membrane bulk porosity. This study shows the effect of different types of MOF particles in MOF-based porous matrix FO substrate for controlling the ICP in FO application for the first time, which provides an additional dimension for ICP control in osmotically-driven membrane processes.