Immobilization of laccase on different functional groups and degree of conjugation modified COFs for simultaneous photochemical-enzymatic removal of 2,4-dichlorophenol and uranium (U(vi))†

To fabricate an efficient photocatalyst-enzyme hybrid system (PEHS), laccase immobilization of covalent organic frameworks (COFs) with different pore sizes as well as pore environments was performed to investigate the catalytic performance of simultaneous uranium (U(VI)) photoreduction and 2,4-dichlorophenol (2,4-DCP) photooxidation. The results indicated that (i) Lac@COFs showed satisfactory removal of 2,4-DCP, and the regulation of conjugation degrees and functional groups significantly enhanced the photocatalytic reduction removal performance of U(VI); (ii) the heterogeneous phase Lac@COFs generated a large number of reactive species, such as h⁺, e⁻, ˙O₂⁻, ˙OH and H₂O₂, which were used for 2,4-DCP degradation and the U(VI) reduction under visible light; (iii) meanwhile, Cu ions at the T1 active site in laccase absorbed e⁻ from 2,4-DCP to further promote the U(VI) photoreduction. Thus, the coupling of laccase immobilization and photocatalytic COFs has led to efficient synergistic removal performance with practical applications. Organic/inorganic pollutants can be removed simultaneously in the enzyme-catalyzed and photocatalytic processes, showing excellent pollutant removal effects.