Robust Zirconium Metal–Organic Framework with Optimal Pore Architecture for Discriminatory and Stoichiometric Naphthalene and Anthracene Separation through a Synergistic Supramolecular Mechanism

Direct and selective adsorption of naphthalene over anthracene in the solid phase by porous materials offers an energy-efficient and environmentally friendly approach toward naphthalene/anthracene purification. However, the exploration on this topic has been rare. In this work, we report the exploitation of a robust zirconium metal-organic framework (Zr-MOF), namely SJTU-9, which exhibits unique sandwich-type aromatic walls and optimal pore dimensions capable of exclusively accommodating naphthalene, leading to discriminatory and stoichiometric separation of an equimolar solid mixture of naphthalene and anthracene at room temperature. Single-crystal X-ray diffraction (SCXRD) studies unambiguously demonstrate that the guest naphthalene molecules are firmly trapped within the sandwich-type pockets via equidistant π···π interactions. This optimal confinement, dictated by the pore dimension of the Zr-MOF, further promotes the formation of paired intermolecular van der Waals interactions among the naphthalene guests within the three-dimensional porous space─a structural feature that is key to the exceptional naphthalene/anthracene adsorption selectivity. SJTU-9 represents a unique example of a chemically stable and scalable MOF that holds potential for facile, selective, and recyclable extraction of naphthalene from anthracene.