Melamine-containing co-polyimide membranes for natural gas separation

A melamine-containing copolyimide comprising:

• a structural repeat unit of Formula (I):
• and
• a structural repeat unit of Formula (II):
• wherein:
• Ring moiety A is selected from phenylene, biphenylene, terphenylene, and polycyclic aromatic hydrocarbon, wherein the phenylene, biphenylene, terphenylene, and polycyclic aromatic hydrocarbon are each optionally substituted with one, two, three, or four independently selected R4;
• X and Y are each independently selected from a bond, —O—, —C(O)—, —O-phenyl-C1-4 alkylene-phenyl-O—, and C1-4 alkylene optionally substituted with one, two, three, or four independently selected R5;
• each R1 and R2 is independently selected from halo,C1-4 alkyl, and C1-4 haloalkyl;
• R3 is selected from H, —OH, halo, C1-6 alkyl, C1-6 haloalkyl, phenyl, C1-4 alkyl-phenyl, C3-20 cycloalkyl, C6-20 aryl, C6-20 heteroaryl, C6-20 heterocycloalkyl, and —NRaRb, wherein Ra and Rb are each independently selected from H and C1-6 alkyl, wherein the C1-4 alkyl-phenyl, C3-20 cycloalkyl, C6-20 aryl, C6-20 heteroaryl, and C6-20 heterocycloalkyl are each optionally substituted with one, two, three, or four independently selected R6;
• each R4, R5, and R6 is independently selected from hydrogen, halo, —OH, —NH2, —SH, —C(O)OH, —N3, and C1-4 alkyl optionally substituted with one, two, three, or four independently selected R7, wherein each R7 is independently selected from hydrogen, halo, —OH, —NH2, —SH, —C(O)OH, and —N3;
• a and b are each independently 0, 1, 2, or 3;
• and m+n=1.