Ultrathin c-oriented Cu-TCPP membrane towards shape-selective molecular separation

Highly c-oriented Cu-TCPP ultrathin membrane was prepared through in-situ conversion method. • Green solvents and minimal amount of ligand were used in membrane preparation process. • The membrane can efficiently discriminate linear molecules from non-linear and non-planar molecules. • The shape-based separation mechanism was verified by DFT calculation. Efficient separation of molecules with similar molecular weights is highly demanded in chemical and pharmaceutical industries, yet still hard to achieve with traditional polymer-based membranes. Metal-organic framework (MOF) membranes, especially ultrathin two-dimensional (2D) MOF membranes, offer a good opportunity for realizing these separations. However, current 2D MOF membranes are mainly prepared through the deposition method, which can bring uncertainty to the pore channels, compromising the separation ability. This work reports the preparation of a highly c-oriented ultrathin Cu-TCPP membrane through an electrostatic-assisted in-situ oriented transformation strategy using electrostatically adsorbed copper hydroxide nanostrands as a precursor layer. The resultant membrane has explicit transport channel to be the pores of Cu-TCPP, which enables the efficient discrimination of linear molecules from non-linear and non-planar molecules with similar and even lower molecular weights. Both the experimental work and density functional theory calculations confirm the sieving effect of the Cu-TCPP membrane towards two model molecules (methyl orange and hematoxylin). This work provides a paradigm for fully utilizing the potential of MOF membranes in the precise separation of molecules with similar molecular weights. Effective nanofiltration separation of molecules with similar molecular weights based on steric shape difference is enabled by the ultrathin c-oriented Cu-TCPP membrane prepared through a green and facile electrostatic assisted in-situ conversion strategy Download: Download high-res image (321KB) Download: Download full-size image