Enhancing the natural gas upgrading and acetylene extraction performance of stable zirconium-organic frameworks PCN-605 by ligand functionalization. Issue 5 (October 2022)

• Record Type: Journal Article
• Authors: Hao, Chunlian; Zhu, Houyu; Ren, Hao; Chi, Yuhua; Zhao, Wen; Liu, Xiuping; Guo, Wenyue
• Is Part Of: Journal of environmental chemical engineering. Volume 10:Issue 5(2022)
• Publication Date: 2022-10
• Subjects: Zirconium metal–organic frameworks -- Ligand functionalization -- Acetylene extraction -- Natural gas upgrading -- Molecular simulation; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2022.108383
• Languages: English
• ISSNs: 2213-2929

Abstract

Abstract: Exploring stable adsorbents for efficient separation of C2 H2 and CO2 from CH4 is of great significance to meet the requirements of natural gas upgrading and high-purity C2 H2 production. Despite excellent structure stability and large surface area/pore volume, low adsorbate affinity and co-adsorption of mixtures in zirconium-organic frameworks (Zr-MOFs) seriously limit their applications in gas separation. To overcome these limitations, we designed a series of stable adsorbents based on Zr-based PCN-605 by replacing two H atoms from two central ligand-aromatic rings with different functional groups (–F, –OH, –NH2, –SO3 H, and –SO3 Ag), which are expected to gain steric hindrance effect and charge-tuning effect in varying degrees. The adsorption and separation performances of C2 H2 /CH4 and CO2 /CH4 in PCN-605 materials were theoretically investigated by combining grand canonical Monte Carlo and density functional theory. Thereinto, PCN-605-SO3 Ag shows the largest selectivity of C2 H2 /CH4 (1031.5) and CO2 /CH4 (271.1) under molar ratio 1:99 at 298 K, or increased by 43.3 and 11.9 times, as against the parent PCN-605. This improvement is attributed to a good synergism of steric hindrance effect with charge-tuning effect exerted by –SO3 Ag, which modifies not only the pore surface structure but also the charge distribution, favoring special three-way adsorption to recognize C2 H2, strengthening CO2 affinity with –SO3 Ag, but suppressing CH4 uptake, etc. This work highlights the effect of precise surface-structure and charge-distribution control by ligand functionalization on C2 H2 /CH4 and CO2 /CH4 separation in PCN-605 materials, and provides a feasible strategy to design function-oriented Zr-MOF adsorbents for applications of natural gas upgrading and C2 H2 extraction. Graphical Abstract: The good synergism of steric hindrance effect with charge-tuning effect exerted by –SO3 Ag in Zr-based PCN-605 contributes more greatly to improving the separation of C2 H2 /CH4 and CO2 /CH4 at lower pressures and lower concentrations of C2 H2 and CO2 . ga1 Highlights: Stable Zr-based PCN-605 with ligand functionalization is explored. Separating C2 H2 and CO2 from CH4 is studied by GCMC and DFT. PCN-605-SO3 Ag shows the highest C2 H2 /CH4 and CO2 /CH4 selectivity. Effects of functional groups on gas separation in PCN-605 are deeply analyzed. Cooperation of steric hindrance and charge-tuning exerted by –SO3 Ag dominates.