The paper describes how the ultramicroporous adsorbent Zn-fa-atz (2) – where fa stand for fumaric acid and atz for 3-amino-1,2,4-triazolate – can be used for effective one-step ethylene production from the quaternary CO₂/C₂H₂/C₂H₄/C₂H₆ mixture. Based on the experimental and simulated breakthrough data, it reports how the Zn-fa-atz (2) coordination network synchronously weakens the affinity for three C₂ hydrocarbons, including C₂H₄, while enhancing CO₂ adsorption due to optimized CO₂-host interaction and faster CO₂ diffusion.

The paper concludes that precise control of the adsorption selectivity of C₂H₄ in the complex separation systems can be achieved through fine-tuning of the size and shape of the pores, and of the local pore chemistry. The presented design principles could be helpful to advance the synthesis and application of this new-generation physisorbent for more complex industry-related separation systems.

Abstract of the paper

Purification of ethylene (C₂H₄) as the most extensive and output chemical, from complex multi-components is of great significance but highly challenging. Herein we demonstrate that precise pore structure tuning by controlling the network hydrogen bonds in two highly-related porous coordination networks can shift the efficient C₂H₄ separation function from C₂H₂/C₂H₄/C₂H₆ ternary mixture to CO₂/C₂H₂/C₂H₄/C₂H₆ quaternary mixture system. Single-crystal X-ray diffraction revealed that the different amino groups on the triazolate ligands resulted in the change of the hydrogen bonding in the host network, which led to changes in the pore shape and pore chemistry. Gas adsorption isotherms, adsorption kinetics and gas-loaded crystal structure analysis indicated that the coordination network Zn-fa-atz (2) weakened the affinity for three C2 hydrocarbons synchronously including C₂H₄ but enhanced the CO₂ adsorption due to the optimized CO₂-host interaction and the faster CO₂ diffusion, leading to effective C₂H₄ production from the CO₂/C₂H₂/C₂H₄/C₂H₆ mixture in one step based on the experimental and simulated breakthrough data. Moreover, it can be shaped into spherical pellets with maintained porosity and separation performance.

Paper details

Yang, R., Wang, Y., Cao, JW. et al.: Hydrogen bond unlocking-driven pore structure control for shifting multi-component gas separation function. Nat Commun 15, 804 (2024). DOI: 10.1038/s41467-024-45081-w