“…Upper bound plot for selected cross-linked membranes of CO 2 /CH 4 , Polymers are labelled as follows: (1) PPM-Ƴ-CD-425 (Askari et al, 2012), (2) BMPI-60%-450 (Xu et al, 2021a), (3) 75%-X-PI , (4) 6FDA-DAT/DATCA-450 (Tian et al, 2018), (5) 6FDA-DAT1-450-3h (Yerzhankyzy et al, 2022), ( 6) PI-Im-COOH-450-1 (Shi et al, 2022), ( 7) FDA-DAPI-DABA-40min (Dose et al, 2019), ( 8) PIM-BM-70(250C-10h) (Chen et al, 2020), ( 9) PIM-BM-70(300C-5h) (Chen et al, 2020), (10) 50%-X-PI , ( 11) PIM-300-2d (Li et al, 2012). Adapted from (Liu et al, 2023).…”