How Central Metal Ions in MOF Affect the Uranyl Elimination Performance: Insights from Experimental and Theoretical Studies

Abstract Conventional strategies for enhancing the performance of metal‐organic framework (MOF) adsorbents primarily focus on modifying functional groups, while the critical role of central metal ions remains underexplored. Herein, a definitive structure‐activity relationship governing uranyl (U(VI)) elimination by engineering isomorphic HHTP MOFs (HHTP = 2,3,6,7,10,11‐hexahydroxytriphenylene) with Zn 2+ , Ni 2+ , and Cu 2+ centers is revealed. Advanced characterization confirms that the identity of the metal dictates electronic configurations and binding thermodynamics without altering crystallographic topology. Remarkably, Zn‐HHTP achieves a record U(VI) uptake capacity of 458.73 mg·g −1 , surpassing Ni‐HHTP (441.27 mg·g −1 ) and Cu‐HHTP (317.24 mg·g −1 ), coupled with ultrafast kinetics (80 min) and exceptional selectivity. Mechanistic studies reveal that the optimal electronegativity (χ = 1.65) of Zn 2+ endows it with superior Lewis acidity, facilitating enhanced charge transfer (Δq = 0.065 e − ) via Zn─O─U coordination, as demonstrated by combined XPS analysis and DFT calculations. This lower electronegativity of Zn 2+ promotes greater electron acceptance from U‐O, yielding a robust binding energy ( E ads = −35.16 kcal·mol −1 ). This work establishes the modulation of central metal ions as a critical design paradigm for next‐generation MOF adsorbents, positioning Zn‐HHTP as a transformative material for high‐efficiency radioactive wastewater remediation.