Molecular Trapdoor in HEU Zeolite Enables Inverse CO<sub>2</sub>‐C<sub>2</sub>H<sub>2</sub> Separation
Jizhen Jia, Nana Yan, Xin Lian, Shanshan Liu, Shanshan Liu, Bin Yue, Yuchao Chai, Guangjun Wu, Jian Xu, Landong Li
Abstract
Abstract The adsorptive separation of molecules with very similar physical properties is always a challenging task. Reported herein is the design and tailoring of zeolite adsorbent for the precise discrimination and separation of CO 2 ‐C 2 H 2 mixture through the pronounced trapdoor effect. Typically, Sr exchanged K‐type clinoptilolite, namely Sr/K‐HEU, is developed as a robust zeolite adsorbent for inverse CO 2 ‐C 2 H 2 separation, showing the‐state‐of‐the‐art dynamic CO 2 /C 2 H 2 selectivity of 48.0 and sustainable CO 2 dynamic uptake of 0.96 mmol/g at the same time. The perfect recyclability and the intrinsic low‐cost nature of Sr/K‐HEU make it a promising candidate for practical applications. Three‐dimensional electron diffraction determines the precise structure of Sr/K‐HEU and density functional theory calculations reveal the intricate interplay between guest molecules and the gate‐keeping extraframework cations. Briefly, extraframework Sr 2+ cations from the ten‐membered rings of HEU zeolites act as the molecular trapdoor, allowing the entry of CO 2 molecules while excluding C 2 H 2 . This work presents a new example of molecular trapdoor in zeolite and its successful application in the challenging inverse CO 2 ‐C 2 H 2 separation, which not only expands the scope of molecular trapdoor concept but also improves current understanding on the nature of molecular trapdoor.