CTAB assisted evaporation-induced self-assembly to construct imidazolium-based hierarchical porous covalent organic...

Evaporation-induced self-assembly method (EISA) was a facile and reliable method to synthesize porous materials. Herein, we report a kind of hierarchical porous ionic liquid covalent organic polymers (HPnDNH₂) under cetyltrimethylammonium bromide (CTAB) assisted by EISA for ReO₄^-/TcO₄^- removal. Unlike covalent organic frameworks (COFs), which usually needed to be prepared in a closed environment or with a long reaction time, HPnDNH₂ in this study was prepared within 1 h in an open environment. It was worth noting that CTAB not only served as a soft template for forming pore, but also induced ordered structure, which was verified by SEM, TEM, and Gas sorption. Benefit from its hierarchical pore structure, HPnDNH₂ exhibited higher adsorption capacity (690.0 mg g^-1 for HP1DNH₂ and 808.7 mg g^-1 for HP1.5DNH₂) and faster kinetics for ReO₄^-/TcO₄^- than 1DNH₂ (without employing CTAB). Additionally, the material used to remove TcO₄^- from alkaline nuclear waste was seldom reported, because combining features of alkali resistance and high uptake selectivity was not easy to achieve. In this study, in the case of HP1DNH₂, it displayed outstanding adsorption efficiency toward aqueous ReO₄^-/TcO₄^- in 1 mol L^-1 NaOH solution (92%) and simulated Savannah River Site High-level waste (SRS HLW) melter recycle stream (98%), which could be a potentially excellent nuclear waste adsorbing material.