Metal–organic frameworks (MOFs) manifest enormous potential in promoting electromagnetic wave (EMW) absorption thanks to the tailored components, topological structure, and high porosity. Herein, rodlike conductive MOFs (cMOFs) composed of adjustable metal ions of Zn, Cu, Co, or Ni and ligands of hexahydroxytriphenylene (HHTP) are prepared to attain tunable dielectric properties for a tailored EMW absorption. Specifically, the influences of the cMOFs’ composition, charge transport characteristic, topological crystalline structure, and anisotropy microstructure on dielectric and EMW absorption performance are ascertained, advancing the understanding of EMW attenuation mechanisms of MOFs. The boosted conductive and polarization losses derived from the conjugation effects and terminal groups, as well as shape anisotropy, lead to a prominent EMW absorption of the cMOFs. The Cu-HHTP confers a minimum reflection loss (RLmin) of −63.55 dB at the thickness of 2.9 mm and a maximum effective absorption bandwidth of 5.2 GHz. Moreover, Zn-HHTP showcases the absorption superiority in the S-band (2–4 GHz) with an RLmin of −62.8 dB at a thickness of 1.9 mm. This work not only hoists the mechanistic understanding of the structure–function relationships for the cMOFs but also offers guidelines for preparing functional MOF materials.
Owing to their high density of active coordination sites, metal-organic frameworks (MOFs) have been extensively explored for uranium(VI) removal. However, the adsorption performance of pristine ZnHHTP is often limited by strong interlayer π-π stacking interactions, which reduce the effective porosity, hinder mass transport, and restrict the accessibility of uranium-binding sites. Herein, we demonstrate a facile ammonia-triggered assembly and etching strategy to construct defect-rich hierarchical pores within ZnHHTP nanostructures. Morphological and structural characterizations demonstrate that ammonia modulation introduces abundant mesopores into the originally low-porosity framework, creating a hierarchical architecture. This structural evolution leads to a significantly increased specific surface area, enriched defect sites, and enhanced surface hydrophilicity. Consequently, the optimized m-ZnHHTP-25 exhibits outstanding uranium(VI) elimination performance, reaching near-equilibrium within only 100 min and a remarkable maximum adsorption capacity of 521.41 mg·g −1 . Mechanism studies revealed a synergistic effect contributing to the enhanced performance. The hierarchical mesopores function as ion-transport channels, significantly accelerating the mass transfer kinetics. Moreover, the abundant and highly accessible defect sites function as high-density binding locations, where catechol oxygen atoms form strong chemical coordination bonds with UO 2 2+ . This study not only presents a promising candidate material for radioactive wastewater treatment but also offers a powerful protocol for rationally designing hierarchical porosity in porosity-deficient coordination networks for environmental remediation.
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