调控强活性位点的智能光响应CO₂吸附剂

Light-responsive CO₂ adsorbents can effectively adjust their ability to capture CO₂ through external light irradiation, and have the advantages of good controllability and high energy efficiency during the adsorption process. However, the currently reported light-responsive CO₂ adsorbents can only realize the regulation of weak adsorption sites, and the regulation of strong adsorption sites is still a challenging task. In this work, a light-responsive smart adsorbent was constructed by in situ synthesis, and the light-responsive control of strong adsorption sites for CO₂ was realized. The construction of adsorbent was achieved by introducing the azobenzene derivative with cis and trans isomers and silane coupling agent containing primary amines into mesoporous silica. The characterization results show that the adsorbents have uniform pore channels, and primary amine and light-responsive groups are dispersed on the pore walls. The strong interaction between primary amine and CO₂ can lead to the selective adsorption of CO₂, while azobenzene as a molecular switch can regulate the adsorption performance of primary amine. Before light irradiation, azobenzene is in trans configuration, which decreases the electrostatic potential of the primary amine, and exposes the active site, thus CO₂ can be freely adsorbed; after light irradiation, azobenzene is converted to the cis configuration, which increases the electrostatic potential of the primary amine and shields the active sites. The change amount of adsorption capacity can reach 43%, and this process is reversible. Both the light-responsive properties of azobenzene groups and the adsorptive performances of adsorbents can be well maintained after 5 cycles. Azobenzene in different configuration has distinctive influences on the electrostatic potential of primary amine, thereby achieving the regulation of adsorption ability. This work utilizes the specific interaction between stimuli-responsive groups and target-specific adsorption sites, realizing the regulation of strong active cites for CO₂, which gives clues to the development of new smart adsorbents.