Self-adaptive flexible metal-organic framework enables hybrid membrane for enhanced separation of VOCs

Hybrid membranes that incorporate functional fillers into the polymer matrix have emerged as promising membranes for separation of volatile organic compounds (VOCs). However, the pore architectures of the commonly used fillers are usually unable to perfectly match the size of the targets. Excessively large pores will compromise molecular selectivity, while ultramicropores will restrict the permeation properties. Herein, we report a hybrid membrane that incorporates a flexible metal-organic framework (Al-CDC) into poly (ether-block-amide) (Pebax) matrix to create self-adaptive transport pathways for efficient toluene/N 2 separation. The flexible Al-CDC exhibits a stimulus-response upon absorption of toluene, which triggers framework expansion (∼20% unit-cell volume increase) and concurrently imposes enhanced diffusion resistance on weakly interacting N 2 . This dynamic pore-opening and occupation mechanism enables selective absorption and low-resistance permeation of toluene. As a result, the optimized membrane (Pebax-Al-CDC-3) achieves a toluene permeability of 1.48 × 10 −6  mol μm m −2 s −1  Pa −1 and a toluene/N 2 selectivity of 1030 with stable performance over 120 h of continuous operation. Moreover, the developed membrane can also significantly enhance the separation of n -heptane/N 2 , indicating the wide effectiveness towards both aromatic and aliphatic VOCs. This work establishes that integrating flexible MOF fillers with self-adaptive pore regulation offers a promising strategy to overcome the intrinsic selectivity-permeability trade-off, providing new insights into the design of high-performance hybrid membranes for VOCs separation.