Ultrastable Thorium Metal–Organic Frameworks for Efficient Iodine Adsorption

Two novel thorium-based metal-organic frameworks (MOFs), namely Th-SINAP-7 and Th-SINAP-8, have been synthesized via the solvothermal reactions of thorium nitrate and 1,4- or 2,6-naphthalenedicarboxylic acid in the presence of acid modulators. Bearing the rigid aromatic architectures, Th-SINAP-7 and Th-SINAP-8 exhibit exceptional chemical (from pH 1 to 12) and thermal stabilities (up to 520 °C), as well as ionizing radioresistance (2 × 10⁵ Gy β and γ irradiations). The highly porous nature and conjugated π-electrons of naphthalene on the organic linkers endow high affinity of both MOFs toward I₂ molecules owning to the charge transfer between π-electrons of the host networks and the guest iodine molecules, as evidenced by combined techniques including of FTIR, PXRD, SEM-EDS, UV-vis spectroscopy, XPS, and Raman spectroscopy. Particularly, Th-SINAP-8 can efficiently remove >99% I₂ from cyclohexane solution and exhibit guest uptake of iodine vapor with an adsorption capacity of 473 mg/g.