Temperature-dependent rearrangement of gas molecules in ultramicroporous materials for tunable adsorption of CO2 and C2H2
Zhaoqiang Zhang, Yinlin Chen, Kungang Chai, Chengjun Kang, Shing Bo Peh, He Li, Junyu Ren, Xiansong Shi, Xue Han, Catherine Dejoie, Sarah J. Day, Sihai Yang⧫, Dan Zhao
Abstract
Abstract 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.