One-dimensional confinement-induced MOF-in-COF layer on polymeric substrate for helium separation

Hetero-structured nanocomposite membranes have great potential in advanced gas separation due to the synergy of hierarchical pores. Herein, we report a MOF (metal–organic framework)-in-COF (covalent organic framework) layer supported on a polyacrylonitrile (PAN) ultrafiltration substrate prepared by a contra-diffusion reaction of MOF inside a one-dimensional (1D) pore-channels of COF layer. Such 1D confinement-induced membrane features a unique ultramicropore-in-nanopore structure, which intensifies the molecular sieving while preserving high-speed transfer pathways. The prepared ZIF-67-in-TAPB-BPDA-PAN membrane exhibited an excellent helium (He) permeance of ∼1500 GPU together with an enhanced separation selectivities of 3.89 for He/N 2 and 5.38 for He/CH 4 , respectively. The overall performance is competitive among the reported He-selective membranes. A continuous gas permeation test for 100 h indicates good stability. This work would bring insights into the engineering and preparation of nanocomposite functional materials applied in various separation fields.