Modulating conjugated microporous polymers via molecular isomerism engineering for photoenhanced extraction of uranium from rare earth wastewater

When designing new conjugated microporous polymers (CMPs), major efforts are typically focused on selecting specific linkages and variations of building blocks to control their terminal structure and function. However, the constitutional isomerism of CMPs has seldom been considered so far as a crucial aspect. Herein, we successfully synthesize a pair of isomeric CMPs, named DBP-TEP (with phenanthrenequinone units) and DBQ-TEP (with anthraquinone units). Benefiting from the construction of the extended D-π-A conjugated skeleton, our isomeric CMPs are characterized by low band gaps and high charge transport efficiency, thus remarkably enhancing uranium photoreduction performance. Interestingly, the experiment results show that the adsorption capacity of DBP-TEP is 1.5 times that of DBQ-TEP under light irradiation. Additionally, both experiments in real-life and theoretical calculations prove that the phenanthrenonequinone unit does have a profound effect on the photocatalytic activity, which is predominantly attributed to the stronger electronic push-pull system and higher π-conjugated system in DBP-TEP.