RESUMEN
Adsorption and desorption are equally important in an adsorptive separation process, while conventional adsorbents with fixed pores benefit only one of them rather than both. Here, a new generation of adsorbents was fabricated by incorporating thermo-responsive polymers (TRPs) into pores. The TRPs act as molecular switches, making pore spaces and active sites responsive to adsorption/desorption conditions. The adsorbents can thus realize both selective adsorption and efficient desorption, which are extremely desirable for adsorptive separation.
RESUMEN
A smart adsorbent RA@MS is fabricated by incorporating a di-block copolymer through the combination of the thermo-responsive block poly(N-isopropylacrylamide) (R) and the active block poly{N-[3-(dimethylamino) propyl]methacrylamide} (A, tertiary amines as basic sites) into mesoporous silica. The di-block copolymer RA preserves the thermo-responsive nature, which makes the active sites reversibly exposed/blocked in light of temperature variation. The obtained adsorbent possessing thermo-responsive properties can thus realize both selective adsorption and efficient regeneration for temperature-swing adsorption (TSA) of dyes.
RESUMEN
Selective adsorption and efficient regeneration are two crucial issues for adsorption processes; unfortunately, only one of them instead of both is favored by traditional adsorbents with fixed pore orifices. Herein, we fabricated a new generation of smart adsorbents through grafting photoresponsive molecules, namely, 4-(3-triethoxysilylpropyl-ureido)azobenzene (AB-TPI), onto pore orifices of the support mesoporous silica. The azobenzene (AB) derivatives serve as the molecular gates of mesopores and are reversibly opened and closed upon light irradiation. Irradiation with visible light (450 nm) causes AB molecules to isomerize from cis to trans configuration, and the molecular gates are closed. It is easy for smaller adsorbates to enter while difficult for the larger ones, and the selective adsorption is consequently facilitated. Upon irradiation with UV light (365 nm), the AB molecules are transformed from trans to cis isomers, promoting the desorption of adsorbates due to the opened molecular gates. The present smart adsorbents can consequently benefit not only selective adsorption but also efficient desorption, which are exceedingly desirable for adsorptive separation but impossible for traditional adsorbents with fixed pore orifices.