A Single-Molecule Propyne Trap: Highly Efficient Removal of Propyne from Propylene with Anion-Pillared Ultramicroporous Materials

Propyne/propylene (C H /C H ) separation is a critical process for the production of polymer-grade C H . However, optimization of the structure of porous materials for the highly efficient removal of C H from C H remains challenging due to their similar structures and ultralow C H concentration. Here, it is first reported that hybrid ultramicroporous materials with pillared inorganic anions (SiF = SIFSIX, NbOF = NbOFFIVE) can serve as highly selective C H traps for the removal of trace C H from C H . Especially, it is revealed that the pyrazine-based ultramicroporous material with square grid structure for which the pore shape and functional site disposition can be varied in 0.1-0.5 Å scale to match both the shape and interacting sites of guest molecule is an interesting single-molecule trap for C H molecule. The pyrazine-based single-molecule trap enables extremely high C H uptake under ultralow concentration (2.65 mmol g at 3000 ppm, one C H per unit cell) and record selectivity over C H at 298 K (>250). The single-molecule binding mode for C H within ultramicroporous material is validated by X-ray diffraction experiments and modeling studies. The breakthrough experiments confirm that anion-pillared ultramicroporous materials set new benchmarks for the removal of ultralow concentration C H (1000 ppm on SIFSIX-3-Ni, and 10 000 ppm on SIFSIX-2-Cu-i) from C H .