High toluene uptake at a trace concentration in a novel gallium-based metal–organic framework

Abstract

A novel gallium-based MOF, termed Ga-BPT_SC (single crystal) and Ga-BPT_P (powder), was synthesized. Structural analysis reveals that Ga-BPT_SC and Ga-BPT_P are isostructural with a slight difference in the unit cell parameters. Specifically, both Ga-BPT_SC and Ga-BPT_P are constructed from a trinuclear gallium oxide cluster and BPT³⁻ linker, consisting of a 3D structure with unique micro-channels decorated with small adsorption cavities (∼6.5 Å). These structural features enable Ga-BPT_P to adsorb a significant amount of toluene and xylenes at trace levels (toluene and xylene uptakes of 6.29 mmol g⁻¹ at P/P₀ = 0.005 and ∼6.1 mmol g⁻¹ at P/P₀ = 0.01, respectively). The toluene uptake of Ga-BPT_P exceeds that of the recently reported MOFs, ZJU-520 and ZJU-620, as well as benchmark MOFs (e.g. UiO-66 and HKUST-1) at P/P₀ = 0.005. Moreover, the breakthrough toluene capture of Ga-BPT_P at 200 ppm reveals an uptake of 4.89 mmol g⁻¹, which is considerably higher than that of the benchmark MOFs (e.g. ZIF-8, MIL-100, MIL-101, UiO-66, HKUST-1 and UiO-66-NH₂). The development of the Ga-BPT synthetic protocol and its exceptional adsorption and separation capacities pave the way to the discovery and application of a new class of gallium-based MOFs constructed from trinuclear gallium oxide clusters.