Selective recognition and enrichment of C70 over C60 using an anthracene-based nanotube

Abstract

Selective recognition and enrichment of fullerenes (e.g., C₆₀ and C₇₀) remains challenging due to the same diameter and geometrical similarity. Herein, we report a hexagonal anthracene-based nanotube (1) through a one-pot Suzuki–Miyaura cross-coupling reaction. With anthracene-based side walls and pyridine linkers, 1 features a nano-scale tubular cavity measuring 1.2 nm in diameter and 0.9 nm in depth, along with pH-responsive properties. Interestingly, the electron-rich 1 shows high binding affinity (K_a ≈ 10⁶ M⁻¹) and selectivity (K_s ≈ 140) to C₇₀ over C₆₀ in toluene, resulting from their different contribution of π–π interactions with the host. The protonation of 1 simultaneously alters the electronic properties within the nanotube, resulting in the release of the fullerene guests. Lastly, the selective recognition and pH stimuli-responsive properties of the nanotube have been utilized to enrich C₇₀ from its low-content mixtures of fullerenes in chloroform.