Ultrastable Thorium Metal–Organic Frameworks for Efficient Iodine Adsorption

Abstract

Two\nnovel thorium-based metal–organic frameworks (MOFs), namely <b>Th-SINAP-7</b> and <b>Th-SINAP-8</b>, have been synthesized\nvia the solvothermal reactions of thorium nitrate and 1,4- or 2,6-naphthalenedicarboxylic\nacid in the presence of acid modulators. Bearing the rigid aromatic\narchitectures, <b>Th-SINAP-7</b> and <b>Th-SINAP-8</b> exhibit exceptional chemical (from pH 1 to 12) and thermal stabilities\n(up to 520 °C), as well as ionizing radioresistance (2 ×\n10⁵ Gy β and γ irradiations). The highly porous\nnature and conjugated π-electrons of naphthalene on the organic\nlinkers endow high affinity of both MOFs toward I₂ molecules\nowning to the charge transfer between π-electrons of the host\nnetworks and the guest iodine molecules, as evidenced by combined\ntechniques including of FTIR, PXRD, SEM-EDS, UV–vis spectroscopy,\nXPS, and Raman spectroscopy. Particularly, <b>Th-SINAP-8</b> can efficiently remove >99% I₂ from cyclohexane solution\nand exhibit guest uptake of iodine vapor with an adsorption capacity\nof 473 mg/g.