Adjustable free volume of polyamide membrane medicated by confined organic alkane molecules for efficient hydrogen separation.

[Display omitted] • Polyamide membranes were fabricated using an in-situ confinement strategy. • Alkane molecules with different alkyl chains were confined in polyamide network. • Membrane microstructure was dynamicly regulated upon thermal stimulation. • Membrane exhibited excellent H 2 separation performance and stability at 100 °C. Rational design of polyamide cross-linked network is of vital significance for fabricating advanced separation membranes. Herein, polyamide membranes with tunable free volume cavity are constructed utilizing an in-situ confinement strategy during interfacial polymerization process, where organic alkane molecules with different alkyl chain such as n-octane, n-dodecane, and n-hexadecane are confined in stiff polyamide skeleton and entangled with nearby polyamide chains. The efficient confinement of organic alkane molecules is confirmed by thermogravimetric coupled with mass spectrometry analysis, and corresponding variations in chain architecture of polyamide network are verified by X-ray diffraction and positron annihilation lifetime spectroscopy techniques. Upon thermal stimulation, the inherent flexibility of confined organic alkane molecules along with stiffness of polyamide skeleton, allow enlargement of chain d-spacing and dynamic regulation of membrane microstructure for fascinating H 2 permeation separation. The optimized modified membrane exhibits a H 2 permeance of 116.1 GPU and a H 2 /CH 4 selectivity of 70.8, which can be stably operated at 100 °C for over 400 h. This study provides a deep understanding of polyamide membranes with confinement of organic molecules and thermally induced separation performances, advancing the design of novel membranes with promising H 2 separation performances at elevated temperatures. [ABSTRACT FROM AUTHOR]