Synthesis and Gas Separation of HOF-21/Triphenylamine Polyimide Mixed Matrix Membranes

A novel trianiline diamine monomer, 4,4'-diamino-4-(3,4,5-trimethoxy)triphenylamine (DATT), was synthesized from 3,4,5-trimethoxyaniline and 4-fluoronitrobenzene and copolymerized with 9,9'-bis(4-amino-3-fluorophenyl)fluorene (FFDA) and 4,4'-(hexafluoroisopropylidene) phthalic anhydride (6FDA) to prepare a novel category of polyimide MTPI which contains triphenylamine, methoxy, fluorenyl, and hexafluoroisopropylidene groups, mixed matrix membranes (MMMs) of HOF-21/MTPI were prepared by blending with HOF-21. The MMMs exhibits outstanding thermal stability ( T _10% > 278 ℃, T _g > 398 ℃), hydrophobicity (water contact angle > 82°). In terms of gas separation performance, the 4%HOF-21/MTPI exhibit high CO ₂ permeability (29.61 bar) and CO ₂ /N ₂ selectivity (25.32 bar) with improvements of 22.6% and 14.7%, respectively, compared to the substrate membrane, approaching the Robertson upper limit in 2008.