Polymer-functionalized metal-organic framework nanosheet membranes for efficient CO2 capture

Two-dimensional metal-organic frameworks (2DMOFs) have emerged as highly appealing candidates as advanced separation membrane materials. However, constructing 2DMOF membranes with appropriate channel sizes to separate CO 2 from N 2 remains a great challenge. Here, we propose an in-situ crystallization approach to synthesize CO 2 -philic-polymer functionalized Zr-based MOF nanosheets, enabling the fabrication of efficient CO 2 capture membranes. The in-situ MOF crystallization with polyethylenimine (PEI) polymers leads to a uniform distribution of amines, resulting in the formation of PEI-NUS hybrid nanosheet characterized by both high porosity and strong affinity to CO 2 . These nanosheets are assembled into ultrathin lamellar membranes with thicknesses ranging from 40 to 120 nm. The amines of PEI polymers significantly facilitate the CO 2 transfer as reaction carriers, resulting in a substantially improved CO 2 /N 2 separation performance with a CO 2 permeance of 410 GPU and a CO 2 /N 2 selectivity of 90, which are among the best for MOF membranes in CO 2 separation. This in-situ functionalization strategy paves the way for the fabrication of ultrathin 2D membranes for various separations.