Discriminatory Gate‐Opening Effect in a Flexible Metal–Organic Framework for Inverse CO<sub>2</sub>/C<sub>2</sub>H<sub>2</sub> Separation
Weize Wang, Gang‐Ding Wang, Bin Zhang, Xiu‐Yuan Li, Lei Hou, Qing‐Yuan Yang, Bo Liu
Abstract
Abstract Considering the significant application of acetylene (C 2 H 2 ) in the manufacturing and petrochemical industries, the selective capture of impurity carbon dioxide (CO 2 ) is a crucial task and an enduring challenge. Here, a flexible metal–organic framework (Zn‐DPNA) accompanied by a conformation change of the Me 2 NH 2 + ions in the framework is reported. The solvate‐free framework provides a stepped adsorption isotherm and large hysteresis for C 2 H 2 , but type‐I adsorption for CO 2 . Owing to their uptakes difference before gate‐opening pressure, Zn‐DPNA demonstrated favorable inverse CO 2 /C 2 H 2 separation. According to molecular simulation, the higher adsorption enthalpy of CO 2 (43.1 kJ mol −1 ) is due to strong electrostatic interactions with Me 2 NH 2 + ions, which lock the hydrogen‐bond network and narrow pores. Furthermore, the density contours and electrostatic potential verifies the middle of the cage in the large pore favors C 2 H 2 and repels CO 2 , leading to the expansion of the narrow pore and further diffusion of C 2 H 2 . These results provide a new strategy that optimizes the desired dynamic behavior for one‐step purification of C 2 H 2 .