| Summary: | Selective-adsorption separation is an energy-efficient technology for the capture of acetylene (C<sub>2</sub>H<sub>2</sub>) from carbon dioxide (CO<sub>2</sub>) and ethylene (C<sub>2</sub>H<sub>4</sub>). However, it remains a critical challenge to effectively recognize C<sub>2</sub>H<sub>2</sub> among CO<sub>2</sub> and C<sub>2</sub>H<sub>4</sub>, owing to their analogous molecule sizes and physical properties. Herein, we report a new microporous metal–organic framework (<b>NUM-14</b>) possessing a carefully tailored pore system containing moderate pore size and nitro-functionalized channel surface for efficient separation of C<sub>2</sub>H<sub>2</sub> from CO<sub>2</sub> and C<sub>2</sub>H<sub>4</sub>. The activated <b>NUM-14</b> (namely <b>NUM-14a</b>) exhibits sufficient pore space to acquire excellent C<sub>2</sub>H<sub>2</sub> loading capacity (4.44 mmol g<sup>−1</sup>) under ambient conditions. In addition, it possesses dense nitro groups, acting as hydrogen bond acceptors, to selectively identify C<sub>2</sub>H<sub>2</sub> molecules rather than CO<sub>2</sub> and C<sub>2</sub>H<sub>4</sub>. The breakthrough experiments demonstrate the good actual separation ability of <b>NUM-14a</b> for C<sub>2</sub>H<sub>2</sub>/CO<sub>2</sub> and C<sub>2</sub>H<sub>2</sub>/C<sub>2</sub>H<sub>4</sub> mixtures. Furthermore, Grand Canonical Monte Carlo simulations indicate that the pore surface of the <b>NUM-14a</b> has a stronger affinity to preferentially bind C<sub>2</sub>H<sub>2</sub> over CO<sub>2</sub> and C<sub>2</sub>H<sub>4</sub> via stronger C-H···O hydrogen bond interactions. This article provides some insights into customizing pore systems with desirable pore sizes and modifying groups in terms of MOF materials toward the capture of C<sub>2</sub>H<sub>2</sub> from CO<sub>2</sub> and C<sub>2</sub>H<sub>4</sub> to promote the development of more MOF materials with excellent properties for gas adsorption and separation.
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