Encage the Carcinogens: A Metal–“Organic Cage” Framework for Efficient Polycyclic Aromatic Hydrocarbon Removal From Water

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic and persistent organic pollutants in water. Their removal is highly challenging for existing generic and nonspecific adsorbents, creating an urgent need for tailored solutions. Herein, a metal-“organic cage” framework, MOF-CC-1, designed for the effective scavenging of PAHs from water is is introduced. This framework is constructed using a propeller-shaped cofacial organic cage (CC-1), equipped with three triazole pillars that coordinate with Ag(I) ions. The cationic MOF-CC-1 adopts a chiral (10,3)-a srs net structure, spontaneously resolving into homochiral crystals. Additionally, bulk homochirality is achieved through chirality induction using chiral counteranions. MOF-CC-1 uniquely encapsulates diverse PAH molecules within the cavities of CC-1, as confirmed by single-crystal X-ray diffraction, marking it as the first metal–“organic cage” framework with structural evidence of guest inclusion inside the organic cage linker. Further, MOF-CC-1 exhibits soft porosity, remaining nonporous to N₂ gas when compressed but expanding to encapsulate PAHs in solution. Moreover, MOF-CC-1 exhibits exceptional efficacy in scavenging ppb levels of PAHs from water. This work represents a significant advancement in utilizing organic cages as ligands toward MOF construction, paving the way for tailored adsorbents for PAH removal, and addressing a critical need for selective and efficient materials in environmental remediation.