Highly efficient enrichment mechanism of U(VI) and Eu(III) by covalent organic frameworks with intramolecular hydrogen-bonding from solutions

[Display omitted] •TpPa-1 exhibited high sorption capacities for U(VI)/Eu(III).•Intramolecular H-bonding regulated electron density and lowered charge of U(VI)/Eu(III).•The adsorption mechanism of U(VI)/Eu(III) were proposed and TpPa-1 was promising adsorbent. In this investigation, TpPa-1 were synthesized and exploited for radionuclides ions elimination. According to Langmuir model, at pH 6.5 and 298 K, the maximum adsorption quantity of TpPa-1 were 1194.07 mg(U(VI))/g and 1107.63 mg(Eu(III))/g, respectively. The superior adsorption performance could be attributed to: (i) a great quantity of heteroatom activated sites on the pore wall could conduct as cation receptors; (ii) the forming intramolecular CN…H…O hydrogen bonding in the network of TpPa-1, which was U(VI) and Eu(III) ions adsorption sites; (iii) hydrogen bonding could adjust the electron density of the complex and abate the total charge of radionuclides. The outcomes of this work suggest that TpPa-1 is a promising adsorbent, which is appropriate to enrichment and separation radionuclides from polluted wastewater.