Optimal Host–Guest Fit in Metal–Organic Frameworks to Achieve Record C₂H₂ Packing Density for Trace Acetylene Capture

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Summary:
The authors from Shanxi University, Shantou University, China University of Petroleum-Beijing, and University of Limerick developed a dimethyl-functionalized MOF (SXU-10) with record C₂H₂ packing density (483.9 mg cm⁻³ at 1 kPa, 733.97 mg cm⁻³ at 100 kPa), achieving polymer-grade C₂H₄ purification from 1 % C₂H₂/C₂H₄ under 80 % RH.

Background:
1. To remove trace C₂H₂ from C₂H₄, prior MOFs showed trade-offs between capacity/selectivity and suffered from humidity instability.
2. The authors proposed steric-substituent engineering of the CPL-1 platform to optimize host–guest fit and suppress gate-opening, obtaining SXU-10 with steep low-pressure uptake.

Research Content:
1. Synthesis: SXU-10 was synthesized in water at room temperature by slow diffusion of Na₂pzdc into Cu(NO₃)₂ and 2,5-dimethylpyrazine.
2. Characterizations:
   1) BET 232 m² g⁻¹; ultramicropores ~0.5 nm.
   2) Single-crystal X-ray shows isomorphous P2₁/c frameworks with 1D channels.
   3) In-situ C₂H₂-loaded structures, TG (stable to 558 K), PXRD confirm humidity tolerance.
3. Application: Dynamic breakthrough gives 111 min g⁻¹ C₂H₂ retention for 1 % C₂H₂/99 % C₂H₄ at 298 K, 10.3 mL min⁻¹; 48.1 mmol g⁻¹ polymer-grade C₂H₄ produced.
4. Mechanism: Dual methyl groups block metastable sorption sites, constrain gliding flexibility (Δα 2.7° vs 8.0° for CPL-1), and enhance shape complementarity, eliminating gate-opening and boosting trace C₂H₂ uptake.

Outlook:
SXU-10 offers an industrially viable, low-cost, green-synthesized adsorbent for humid C₂H₂/C₂H₄ separation, demonstrating that sub-Å host–guest fit engineering can surpass traditional binding-strength strategies.

Optimal Host–Guest Fit in Metal–Organic Frameworks to Achieve Record C₂H₂ Packing Density for Trace Acetylene Capture
Authors: Jun-Hao Wang, Yu-Chi Wan, Ji-Ning Cao, Ye-Fan Zhang, Rui-Min Wu, Hai-Feng Zhang, Xu-Dong Wu, Jin-Sheng Zou, Mei-Jing Cheng, Yong-Liang Huang, Mian Li, Ying Zhang, Yun-Lei Peng, Michael J. Zaworotko
DOI: 10.1002/anie.202524692
Link: https://onlinelibrary.wiley.com/doi/10.1002/anie.202524692

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