Small molecule DOPO-p-DP crosslinked 6FDA-DAM-Br-85% carbon molecular sieve membrane with superior aging for efficient gas separation

Carbon molecular sieve (CMS), as the gas separation membrane materials, still faces challenges for regulation pore diameter precisely. In this work, we propose to reconstruct the 6FDA-DAM-Br-85% polyimide CMS membranes by introducing 6,6'-(1,4-phenylenebis(((4-hydroxyphenyl)amino)methylene))bis(dibenzo[c,e][1,2] oxaphosphinine6-oxide) small molecule compound (DOPO-p-DP) as crosslinking agent to regulate the pore distribution. The crosslinked precursors were obtained via the reaction between C–Br bond in 6FDA-DAM-Br-85% polyimide and N–H bond in DOPO-p-DP compound, the precursors and CMS membranes (550 °C- 2 h) were characterized with ATR-TFIR, XRD and XPS. The pore size distribution of crosslinked CMS membranes was range in 4.5–8.0 Å from the N2 adsorption data. The crosslinked CMS membranes exhibited excellent gas separation performance, which was strongly dependent on the mass fraction of DOPO-p-DP, an increasing mass fraction of DOPO-p-DP leaded to improve in gas selectivity, while reduced its permeability. The 6FDA-DAM-Br-85%/DOPO-p-DP-20% CMS membrane showed the impressive permeability and superior gas selectivity, the permeabilities of O2, CO2, and H2 are 798, 3018, and 13560 Barrer combined with the O2/N2, CO2/CH4, and H2/CH4 selectivities of 7.8, 65.6, and 294.8 respectively, the separation performances surpassed the latest trade-off relationship. In addition, the 20% of the DOPO-p-DP crosslinked CMS membrane revealed the superior aging behaviour than that of the 6FDA-DAM-Br-85% CMS membrane over 480 h aging under vacuum conditions.