Temperature-dependent rearrangement of gas molecules in ultramicroporous materials for tunable adsorption of CO(2) and C(2)H(2)

The interactions between adsorbed gas molecules within porous metal-organic frameworks are crucial to gas selectivity but remain poorly explored. Here, we report the modulation of packing geometries of CO(2) and C(2)H(2) clusters within the ultramicroporous CUK-1 material as a function of temperature. In-situ synchrotron X-ray diffraction reveals a unique temperature-dependent reversal of CO(2) and C(2)H(2) adsorption affinities on CUK-1, which is validated by gas sorption and dynamic breakthrough experiments, affording high-purity C(2)H(2) (99.95%) from the equimolar mixture of C(2)H(2)/CO(2) via a one-step purification process. At low temperatures (<253 K), CUK-1 preferentially adsorbs CO(2) with both high selectivity (>10) and capacity (170 cm(3) g(−1)) owing to the formation of CO(2) tetramers that simultaneously maximize the guest-guest and host-guest interactions. At room temperature, conventionally selective adsorption of C(2)H(2) is observed. The selectivity reversal, structural robustness, and facile regeneration of CUK-1 suggest its potential for producing high-purity C(2)H(2) by temperature-swing sorption.