Architectured Mesoporous Vaterite Nanohourglasses for High-Efficiency Uranium Capture

Developing high-efficiency materials for uranium extraction from seawater is critical to alleviating global uranium resource shortages and advancing sustainable nuclear energy, while it remains a great challenge. Inorganic carbonates are traditionally regarded as poor uranium capture materials due to low capacity and slow kinetics, but this work challenges this notion via structural and crystalline phase engineering and, for the first time, clarifies the phase-dependent capture mechanism. A novel vaterite mesoporous CaCO₃ (V-mCaCO₃) with uniform nanohourglass architecture is synthesized via a triethylamine-assisted gas diffusion strategy. By adjusting the Ca²⁺/CO₃^2- feeding ratio or introducing shear force, the morphology was precisely tailored to nanospindles or nanodiscs. Compared to conventional calcite, vaterite CaCO₃ exhibits exceptional uranium capture performance, with a high saturation capacity of 1325 mg U/g and a record seawater extraction capacity of 125 mg U/g, along with outstanding selectivity against interfering ions. Density functional theory (DFT) calculations reveal that the layered crystal structure of vaterite enables rotation of CO₃^2- groups parallel to the c-axis, enhancing uranium affinity through multidentate coordination with uranyl. Stronger electron localization and binding at the uranyl-vaterite interface (vs calcite) and a more negative adsorption energy (-6.32 eV) for uranyl carbonate complexes in seawater confirm its superior activity. This finding not only provides fundamental insights into structure-activity relationships in mineral-based capture materials but also establishes a new strategy for designing advanced materials for sustainable uranium recovery from seawater.