The diversity of metal–organic frameworks enables the design of highly efficient adsorbents and membranes towards hydrocarbon separations for energy consumption mitigation.

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 .

Here we demonstrate the deep removal of SO 2 with high uptake capacity (1.55 mmol g À1) and record SO 2 /CO 2 selectivity (> 5000) at ultra-low pressure of 0.002 bar, using ionic ultramicroporous polymers (IUPs) with high density of basic anions. The successful construction of uniform ultramicropores via polymerizing ionic monomers into IUPs enables the fully exploitation of the selective anionic sites. Notably, the aperture size and surface chemistry of IUPs can be finely tuned by adjusting the branched structure of ionic monomers, which play critical roles in excluding CH 4 and N 2 , as well as reducing the coadsorption of CO 2. The swelling property of IUPs with adsorption of SO 2 contributed to the high SO 2 uptake capacity and high separation selectivity. Systematic investigations including static gas adsorption, dynamic breakthrough experiments, stability tests and modeling studies confirmed the efficient performance of IUPs for trace SO 2 capture.

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