Simulation insights into the spirobifluorene aryl diamine (SBAD-1)/porous organic cage mixed-matrix membranes for organic solvent nanofiltration

Mixed-matrix membranes (MMMs) have emerged as promising materials for organic solvent nanofiltration (OSN) applications due to their potential to synergize polymer and porous nanomaterials. Theoretically understanding the role of nanofillers within MMMs in determining the OSN performance is crucial for the development of new MMMs. In this work, the molecular simulations are performed to investigate the swelling process and OSN performance of the spirobifluorene aryl diamine (SBAD-1)/porous organic cage (POC) MMMs. Three POCs (i.e., CC3, CC5, and CC17) and three organic solvents (i.e., methanol, acetonitrile, and acetone) are studied. The pure SBAD-1 and pure POC membranes are also constructed for comparison. Results show that the attractive interactions between SBAD-1 and POC can restrict the flexibility of polymer chains, and thereby decrease the dilation of polymer matrix and also the porosity of swollen MMM. Based on this, the solvent resistant property and dye rejection would be well enhanced. Moreover, compared with pure SBAD-1 and pure POC membranes, the solvent permeabilities through swollen MMMs are found to drop due to the blockage of POC pores by SBAD-1 chains and the smaller porosity in membrane. This work reveals the pivotal role of interaction between SBAD-1 and POC in the swelling and OSN performance of SBAD-1/POC MMMs, and would provide theoretical support for the development of MMMs for OSN applications.