A Thermally Promoted Homogenous-Floating-Concentrating Strategy Synthesizing Highly Crystalline...

In this work, a "thermally promoted homogenous-floating-concentrating" strategy is reported for the rapid synthesis of highly crystalline triazine/hydroxyl-rich COFs under mild conditions, using for the effectively adsorbing 4-nitrophenol (4-NP) in aqueous solutions. This strategy originates from an optimized "homogenous-floating-concentrating" method as reported in the previous work. Both gradually improving concentration and heat treatment promote the condensation reaction between amino and aldehyde groups, resulting in high crystallinity and shorter reaction time. The obtained COFs demonstrate better crystallinity and higher surface area in comparison with the counterparts prepared by solvothermal strategy. A maximum surface area of 2391 m² g^-1 is achieved. The COFs exhibit excellent 4-NP adsorption capacity (Q_max = 1402.0 mg g^-1 ), which is attributed to abundant triazine/hydroxyl-groups on the COF skeleton and their strong H-bonding interaction with 4-NP.