Based on the NH4Cl-catalyzed cycloaddition reaction between nitriles and azides, tetrazole polyacrylonitrile (TZPAN) copolymers were synthesized. The copolymers were further modified through alkylation reaction with bromodecane and bromohexadecane, respectively, to obtain alkylated TZ-PAN (D-TZ-PAN and H-TZ-PAN). The successful alkylation via the tetrazole group was confirmed by H-1 NMR spectroscopy, and the degree of functionalization (DF) was well controlled by the doses of reactants (NH4Cl and NaN3). Porous membranes of D-TZ-PAN and H-TZ-PAN were prepared via nonsolvent induced phase separation. Due to the hydrophobic nature of the long alkyl chain, the hydrophobicity of the alkylated PAN membranes was improved. The water contact angle was 113 +/- 2 degrees for D-TZ-PAN with DF of 20% (D-TZ-PAN-20), much higher than that for the pristine PAN membrane (88 +/- 1 degrees). Both D-TZ-PAN and H-TZ-PAN membranes were used in a membrane contactor for CO2 absorption. The improvement in membrane hydrophobicity enhanced the wetting resistance as well as the CO2 absorption flux. The absorption flux at a water flow rate of 240 mL min(-1) was 1.897 mmol m(-2) s(-1) for D-TZ-PAN-20 membrane, 2.5 times higher than that for the pristine PAN membrane. This study proposed a novel method to fabricate hydrophobic PAN membrane and expanded its use for CO2 absorption.