Customizing Pore System in a Microporous Metal–Organic Framework for Efficient C(2)H(2) Separation from CO(2) and C(2)H(4)

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