Orientation-controlled two-dimensional Zr-MOF nanosheet membranes for efficient CO₂ capture

We report orientation-controlled synthesis of zirconium-based MOFs (Zr-MOFs) in which lowering DMF concentration transforms 3D UiO-66 nanoparticles into 2D MIL-140A nanosheets (Zr-DMF50). Supported Zr-DMF50 membranes grown on a porous support exhibit continuous leaf-like morphology, maintain the MIL-140A phase, and display molecular-sieving capability beyond Knudsen transport behavior. Furthermore, exfoliation of bulk Zr-DMF50 powder yields high-aspect-ratio nanosheets that disperse stably in polar solvents and integrate uniformly within a 6FDA-DAM polymer matrix. The resulting mixed matrix membranes (MMMs) show stronger filler–polymer interactions and enhanced mechanical properties compared to those with 3D fillers. Remarkably, a small loading (6 wt%) of 2D nanosheets achieves CO₂ permeability comparable to 20 wt% 3D nanoparticles while simultaneously enhancing CO₂/N₂ selectivity. These performance gains originate from increased diffusivity selectivity, whereas solubility selectivity remains unchanged. In addition, nanosheet-based MMMs exhibit enhanced resistance to CO₂ plasticization, with onset pressures of ∼25 bar. These findings demonstrate that 2D Zr-MOF nanosheets, synthesized through simple solvent concentration control, provide a promising route to highly selective and stable membranes for post-combustion CO₂ capture.