Huaixin Hao

A novel macrocyclic ion receptor has been designed by anchoring twelve 2,6-bis-triazolyl-pyridine (PyTri) units onto a pillar[6]arene platform, which demonstrates outstanding Am/Eu selectivity under highly acidic conditions.

Three new hydrophilic N-donor bistriazolyl-based CHON-compliant ligands with different selectivity for Am vs. Eu and different solubility in aqueous media.

Addressing the challenges of nuclear waste management and strategic resource recovery necessitates novel functional materials for the integrated and efficient capture of critical elements. This work reports a class of multifunctional eutectic mixtures (EMs) constructed from crown ether (hydrogen‐bond acceptor, HBA) and partially esterified organophosphorus acids (hydrogen‐bond donor, HBD). This design integrates the high selectivity of crown ether toward Sr(II) with the strong affinity of organophosphorus ligands for U(VI)/Pu(IV), achieving unprecedented single‐step extraction efficiencies exceeding 99.9% for U(VI), 99.8% for Pu(IV), and 99% for Sr(II) under extreme and nearly realistic conditions. This exceptional performance originates from the differentiated metal coordination of crown ether and phosphoric esters, coupled with a synergistic “coordination‐encapsulation” effect mediated by the formation of reverse micellar supramolecular structures. Our findings not only provide high‐performance materials for the simultaneous recovery of critical radionuclides but also demonstrate the great potential of EMs as a sustainable platform for addressing complex separation scenarios.

The pentavalent neptunyl ion (Np(V)) is the most stable form of neptunium in aqueous solutions. Studying its complexation is essential for developing ligands for Np separation and environmental management. This work investigates Np(V) complexation with three aromatic substituted amidoxime ligands: Benzamidoxime (BzAO), 2-Pyridylamidoxime (Py-2-AO), and 3-Pyridylamidoxime (Py-3-AO). Speciation and stability constants were determined by spectrophotometric titrations, while coordination structures were optimized using DFT calculations. The coordination strength follows the order: Py-2-AO > Py-3-AO > BzAO. Py-2-AO exhibits the strongest coordination due to a synergistic chelation from its pyridine and amidoxime N atoms in the equatorial plane. DFT results confirm that Py-2-AO forms the most stable complex via a five-membered chelate ring, displacing two equatorial water molecules. In contrast, BzAO and Py-3-AO primarily bind in a bidentate fashion through the amidoxime O and N atoms, wherein each ligand also displaces two water molecules. These findings offer fundamental insights for designing effective Np(V) ligands for separation and remediation.

The extraction and complexation of trivalent americium (Am) and lanthanides (Ln) using an asymmetric picolinic acid-derived tridentate N,O-hybrid ligand, 6-(dioctylcarbamoyl)picolinic acid (DOAPA), have been studied through both experimental and theoretical methods. DOAPA exhibits effective and fast extraction of Am(III) and Ln(III). The extraction is driven by favorable enthalpy change. Slope analysis, absorption spectroscopy and NMR titration indicate that both Am(III) and Ln(III) coordinate with DOAPA to form complexes of a 1 : 3 stoichiometry (metal to ligand). Meanwhile, luminescence and mass spectral studies suggest that three deprotonated tridentate DOAPA ligands (L⁻) substitute all the H₂O molecules in the primary coordination sphere of Eu(III), resulting in the extraction of a neutral complex into the organic phase. Further theoretical calculations reveal that a more robust interaction between DOAPA and Am(III) relative to Eu(III) as well as a higher degree of covalence in Am–N/O bonds than in Eu–N/O bonds leads to slight selectivity of Am(III) over Eu(III).

Mo dramatically boosts the extraction of Np( v ) by TRPO through the catalytic reduction effect in both the aqueous phase and organic phase.

The redox effect in a biphasic extraction system leads to unprecedented stabilization of Am(v) and record high Ln/Am separation factors (>10⁵).

Adding hydrophilic ligands into aqueous solutions for the selective binding of actinides(III) is acknowledged as an advanced strategy in Ln(III)/An(III) separation. In view of the recycling and radioactive waste disposal of the minor actinide, there remains an urgent need to design and develop the appropriate ligand for selective separation of An(III) from Ln(III). Herein, four novel hydrophilic ligands with hard-soft hybrid donors, derived from the pyridine and phenanthroline skeletons, were designed and synthesized as masking agents for selective complexation of An(III) in the aqueous phase. The known N,N,N',N'-tetraoctyl diglycolamide (TODGA) was used as lipophilic extractant in the organic phase for extraction of Ln(III), and a new strategy for the competitive extraction of An(III) and Ln(III) was developed based on TODGA and the above hydrophilic ligands. The optimal hydrophilic ligand of N,N'-bis(2-hydroxyethyl)-2,9-dicarboxamide-1,10-phenanthroline (2OH-DAPhen) displayed exceptional selectivity toward Am(III) over Ln(III), with the concentrations of HNO₃ ranging from 0.05 to 3.0 M. The maximum separation factors were up to 1365 for Eu/Am, 417.66 for Eu/Cm, and 42.38 for La/Am. The coordination mode and bonding property of 2OH-DAPhen with Ln(III) were investigated by ¹H NMR titration, UV-vis spectrophotometric titration, luminescence titration, FT-IR, ESI-HRMS analysis, and DFT calculations. The results revealed that the predominant species formed in the aqueous phase was a 1:1 ligand/metal complex. DFT calculations also confirmed that the affinity of 2OH-DAPhen for Am(III) was better than that for Eu(III). The present work using a competitive extraction strategy developed a feasible alternative method for the selective separation of trivalent actinides from lanthanides.

Two novel bistriazolyl-phenanthroline (BTrzPhen) ligands, bearing benzene-sulphonate (DS-BTrzPhen) and amino-acidic (DAA-BTrzPhen) hydrophilizing moieties were developed and found to be more soluble in aqueous acidic media with improved selectivity for Am(III) over Eu(III) in solvent extraction studies having SF_Eu/Am values reaching >300. The remarkable activities of both ligands suggest that BTrzPhen ligands are generally still worth exploring and improving.