Solution-Processable polyMOF Nanosheets for Fabricating CO2 Separation Membranes

The inferior solution processability of metal-organic frameworks (MOFs) significantly hinders their deployment in membrane-based separations. However, existing modification strategies often involve laborious procedures or lead to unfavorable pore blockage. In this study, we developed a one-step synthesis of solution-processable two-dimensional (2D) polymer-MOF (polyMOF) nanosheets using microporous polymer ligands. Carboxylated polymer of intrinsic microporosity-1 (cPIM-1) ligands enhance the dispersion of the resulting polyMOF nanosheets in various solvents, thereby improving membrane processability. More importantly, the incorporation of microporous ligands well preserves the porosity, overcoming the pore-blocking limitations associated with conventional nonporous polymer modification. The synthesized polyMOF nanosheets exhibit a thickness of approximately 4 nm and lateral dimensions exceeding 10 μm. The cPIM-1 component enhances MOF-CO2 affinity and regulates nanosheet stacking orientation, enabling the formation of efficient CO2 transport channels. These polyMOF nanosheets can be readily assembled into ultrathin lamellar membranes, achieving CO2 permeance exceeding 400 gas permeation units (GPU) and a CO2/CH4 selectivity of 25. Furthermore, owing to their increased organic character, the polyMOF nanosheets can be effectively incorporated into mixed-matrix membranes (MMMs), resulting in improved interfacial compatibility.