Facile preparation of covalent organic frameworks@alginate composite beads for enhanced uranium(VI) adsorption

Covalent organic frameworks (COFs) have broad application prospects in adsorption and separation. Yet, as COFs are generally in powder form, their superior performance at the laboratory scale is difficult to transfer into pilot- or industrial-scale use. Thus, there is a strong and urgent need to structure COFs into monolithic materials. Herein, a facile strategy was developed to prepare COFs@alginate composite beads. Three composite beads comprising different COFs including TpPa-1 (2,4,6-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa-1) as monomers), TpDb (Tp and 2,5-diaminobenzonitrile (Db) as monomers) and TpTt (Tp and 1,3,5-triazine-2,4,6-triamine (Tt) as monomers) with controlled COF loading and product size have been facilely achieved via this strategy, validating the applicability of this method. Furthermore, the representative TpDb@alginate composite beads showed good adsorption performance of uranium(VI) in aqueous solution with high adsorption capacity (635 mg·g−1), good interference immunity and recyclability. This work offers a practical approach for incorporation of COFs into polymer matrix, which can serve as potential adsorbents for radioactive wastewater treatment.Graphical abstract