In situ polymer-grafted ZIF-9-based mixed-matrix membranes for efficient separation of H2 and CO2 from CH4

6FDA-APBIA was in-situ incorporated into the ZIF-9 framework via coordination bonds. • 6FDA-APBIA incorporation effectively increased the ultra-microporous volume of ZIF-9. • polyZIF-9 based MMMs exhibit excellent H 2 /CH 4 and CO 2 /CH 4 separation performance. • pZ9–30 MMM shows 2.2-fold (H 2 /CH 4 ) and 1.4-fold (CO 2 /CH 4 ) selectivity over pure PI. • pZ9–30 MMM has good interfacial compatibility and long-term operational stability. Mixed-matrix membranes (MMMs) have broad application prospects in the field of gas separation, particularly for the efficient separation of H 2 /CH 4 and CO 2 /CH 4 , which is of great significance for hydrogen energy recovery and natural gas purification. This study proposes a strategy to in situ incorporate 6FDA-APBIA polymer into the ZIF-9 framework via coordination bonds, constructing polyimide-based ZIF-9 materials (pZ9) with tunable pore structure. The characterization results confirm that the appropriate incorporation of polymer increased the ultra-microporous volume of ZIF-9 for achieving molecular sieving. Furthermore, pZ9 materials were used as fillers to prepare self-supported MMMs with varying loadings. Notably, the gas permeation tests revealed that the MMM with 30 wt% pZ9 loading exhibited excellent H 2 /CH 4 and CO 2 /CH 4 separation performance (α H2/CH4  ≈ 328.05, α CO2/CH4  ≈ 95.21), both exceeding the corresponding upper bounds. This work provides insights into the design of high-performance MMMs, showing promise for applications in hydrogen recovery and natural gas purification. Download: Download high-res image (100KB) Download: Download full-size image