Synthesis and gas separation properties of polyimide membranes derived from oxygencyclic pseudo-Troger's base

Two neoteric oxygencyclic pseudo-Troger's base (TB) -derived naphthalene diamines characterized by large pi conjugated naphthalene rings and half-open cavity structure unit, 16H-8,16-methanodinaphtho [2,1-d:1',2'-g] (Yampolskii, 2012; Maqsood et al., 2014) [1,3]dioxocine-3,13-diamine (OTB) and its furan-based bicyclic analogue, 7a, 14c-dihydronaphtho [(Xu et al., 2014; Yampolskii, 2012) 2,12,1-b]naphth [1',2':4,5]furo [(Maqsood et al., 2014; Xu et al., 2014) 3,23,2-d] furan-3,12-diamine (FB), were successfully synthesized. Their 6FDA-based polyimides (6FDA-OTB and 6FDA-FB) were obtained for membrane-based gas separation study. 6FDA-OTB and 6FDA-FB exhibited good solubility and excellent thermal stability due to the presence of large pi conjugated aromatic rings and half-open cavity structure unit. The two polymer membranes showed high gas pair selectivity and modest gas permeability as well as good physical aging properties. The 6FDA-FB membrane performed a high selectivity of H-2/CH4 (104.0) and CO2/CH4 (49.1), which arises from the larger permeation activation energy difference of different gases. The performances of 100 days aged 6FDA-OTB and 6FDA-FB membranes are almost overlapped with the 1991 Robeson upper bounds for CO2/CH4 and H-2/CH4. In short, introducing the novel rigid oxygencyclic pseudo-Troger's base into the polyimide chains could make attractive membrane materials for various gas separation applications.

Automated summary

The study successfully synthesized two novel neoteric oxygencyclic pseudo-Troger's base derivatives and prepared them into polyimide membranes for gas separation, showing promising performance such as high gas pair selectivity, moderate gas permeability, and good physical aging properties. Introducing oxygencyclic pseudo-Troger's base into polyimide chains could potentially create attractive membrane materials for various gas separation applications.