Smart Removal of Dye Pollutants via Dark Adsorption and Light Desorption at Recyclable Bi2O2CO3 Nanosheets Interface.

The adsorbents for water treatment and purification are commonly not recyclable because of the lack of a reagent-less "switch" to readily release the adsorbed compounds. Herein, the interface of Bi2O2CO3 (BOC) nanosheets is designed, synthesized, and modified with citric acid, namely, modified Bi2O2CO3 (m-BOC). The m-BOC is able to selectively adsorb methylene blue (MB) in the dark and the adsorbed MB could be released in the light from m-BOC without the addition of any chemicals. The adsorption mechanism is attributed to the electrostatic attraction between positively charged MB and the negatively charged surface of m-BOC. In contrast, the desorption of MB has resulted from the photo-induced charge redistribution on the surface of m-BOC, which unlocks the coordination bond between m-BOC and the carboxylic group. As a result, BOC is recycled. Such a mechanism was verified by both experimental investigation and DFT calculation. This work provides a promising interfacial engineering strategy for the remediation of dye-polluted water and smart separation in chemical engineering.