Fabrication of azobenzene-functionalized porous polymers for selective CO2 capture

Many solid adsorbents have been prepared for the CO₂ capture. In particular, the photoresponsive adsorbents have attracted extensive interests because of their tunable pore structure and variable responsive behaviors provoked by the external light. However, it is challenging to fabricate the photoresponsive adsorbents featured the big CO₂ capacity and high CO₂ selectivity. Herein, copolymerized between 4-phenylazobenzoyl chloride, 2,4,6-trichloro-1,3,5-triazine and melamine, a series of azobenzene-functionalized porous polymers (PTM-AZOs) are successfully synthesized. The PTM-AZOs are verified in possession of proper pore structures, large surface area and photoconductive properties through a series of characterization. The PTM-AZO-2 with the trans-isomerization exhibits the best CO₂ adsorption amount of 2.7 mmol·g^-1 (273 K and 0.1 MPa), while the CO₂/N₂ selectivity can reach 2459 and 607 on the trans- and cis-isomerization, respectively. The regulatable pore structures controlled by the photoresponsive azobenzene groups affect the CO₂ capture performance of the PTM-AZOs.