List of symbols
$b_1$, $b_2$	Langmuir constant ($ba{r}^{-1}$)
$dm/dT$	Change in mass per unit temperature ($mg {}^o{C}^{-1}$)
$D$	Diffusivity (${\mathrm{m}}^2/\mathrm{s}$)
$p$	Pressure ($bar$)
$P$	Permeability (Barrer or $\mathrm{m}\mathrm{o}\mathrm{l}·\mathrm{m}/{\mathrm{m}}^2·\mathrm{s}·\mathrm{b}\mathrm{a}\mathrm{r}$)
$-Q_{st}$	Isosteric heat of adsorption ($kJ mo{l}^{-1}$)
$q$	Adsorbed amount (mmol g−1)
$q_{sat,1}$, $q_{sat,2}$	Saturation loading (mmol g−1)
$R$	Molar gas constant ($J mo{l}^{-1} K^{-1}$)
$S$	Solubility ($\mathrm{m}\mathrm{o}\mathrm{l}/{\mathrm{m}}^3·\mathrm{b}\mathrm{a}\mathrm{r}$)
$T$	Temperature ($K$)
$x_1$, $x_2$	Mole fractions of the adsorbed phase
$y_1$, $y_2$	Mole fractions of the gas phase
$\rho$	Density ($g c{m}^{-3}$)
Abbreviations
6FDA	4,4′-(hexafluoroisopropylidene) diphthalic anhydride
Ac2O	Acetic anhydride
BuI	5-tert-butyl isophthalic acid
C2H4	Ethylene
C2H6	Ethane
CA	Cellulose acetate
Cu(NO3)2.3H2O	Copper(II) nitrate trihydrate
C9H6O6	Trimesic acid
DAM (or TMPDA)	2,4,6-trimethyl-m-phenylenediamine
DBzPBI	Substituted polybenzimidazole
DMAc	Dimethylacetamide
NMP	N-methyl-2-pyrrolidone
ODPA	4,4′-oxydiphthalic anhydride
PBI	Polybenzimidazole
TEA	Triethylamine