Fine tune gas separation property of intrinsic microporous polyimides and their carbon molecular sieve membranes by gradient bromine substitution/removal

Carbazole-Based Polyimide Membranes with Hydrogen-Bonding Interactions for Gas Separation

“…The average interchain spacing and the aggregation state of the prepared membranes were tested by utilizing wide-angle X-ray diffraction (WAXD) on fresh methanol-annealing membranes. As seen in Figure S32 (Supporting Information), both membranes display noncrystalline diffraction peaks, respectively, centering at 14.8 and 15.4° (2θ), , which are mostly ascribed to the chain–chain stacking. Another shoulder peak emerging at ∼27° suggests the presence of the face-to-face π–π stacking within both membranes. ,,, To further study the free volume inside the two membranes, positron annihilation lifetime spectroscopy (PALS) technique, which is frequently utilized to investigate atomic and subnanoscale holes inside polymers, is herein performed on fresh methanol-annealing membranes.…”

“…The average interchain spacing and the aggregation state of the prepared membranes were tested by utilizing wide-angle X-ray diffraction (WAXD) on fresh methanol-annealing membranes. As seen in Figure S32 (Supporting Information), both membranes display noncrystalline diffraction peaks, respectively, centering at 14.8 and 15.4°(2θ), 69,70 which are mostly ascribed to the chain− chain stacking. Another shoulder peak emerging at ∼27°s uggests the presence of the face-to-face π−π stacking within both membranes.…”

Current Progress on Dual‐Layer Hollow Fiber Mixed‐Matrix Membrane in CO2 Capture

“…Besides, inorganic membranes exhibit characteristics of a molecular sieve. Due to their ability to distinguish different gas molecules, depending on size of the pores and its shape, these membranes exhibit remarkably higher gas molecule diffusivity and selectivity [103,104]. Examples of gas separation performance of inorganic membranes reported in the literature are shown in Tab.…”

Carbon molecular-sieve membranes developed from a Tröger’s base polymer and possessing superior gas-separation performance

“…The characteristic high free volume tends to be retained, as evinced by higher gas diffusivity, greater gas sorption uptake (due to more cavities), and a larger population of ultramicropores [20][21][22][23][24]. Additional efforts have likewise observed a direct dependence of CMS transport properties on relevant characteristics of the polyimide precursor [16,17,19,25,26], especially in the case of stiff-chain polymers [27][28][29]. This leads to a accepted rule of thumb: an increase in the rigidity of the precursor chain is accompanied by an increase in the gas permeability of the corresponding CMS.…”