C2H4 and C2H6 adsorption-induced structural variation of pillared-layer CPL-2 MOF: A combined experimental and Monte Carlo simulation study. (8th June 2020)

• Record Type: Journal Article
• Authors: Xiang, Huan; Carter, Joseph H.; Tang, Chiu C.; Murray, Claire A.; Yang, Sihai; Fan, Xiaolei; Siperstein, Flor R.
• Is Part Of: Chemical engineering science. Volume 218(2020)
• Publication Date: 2020-06-08
• Subjects: CPL-2 MOF -- C2H4 -- C2H6 -- Adsorption -- Linker rotation -- Pore expansion; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2020.115566
• Languages: English
• ISSNs: 0009-2509

Abstract

Graphical abstract: Highlights: CPL-2 exhibits gradual and reversible linker rotation upon C2 H4 and C2 H6 adsorption. The gradual structural change of CPL-2 results in a fully reversible isotherm. The linker rotation increases the pore volume, rendering additional adsorption site. The linker rotation enhances C2 H4 and C2 H6 adsorption uptakes ( ca. 60%) at 10 bar. Abstract: Coordination pillared-layer metal-organic frameworks (CPL-MOFs), such as CPL-2, are interesting versatile and porous materials with the potential for gas adsorption and separation. CPL-2 shows the unusual and gradual linker rotation upon the adsorption of ethylene (C2 H4 ) and ethane (C2 H6 ), leading to a fully reversible adsorption isotherm specifically under the conditions studied. Grand canonical Monte Carlo (GCMC) simulations showed that it is impossible to accommodate the experimentally observed loadings of C2 H4 and C2 H6 in CPL-2 using the crystallographic structure reported in the literature. According to the simulation findings, the pore expansion might be initiated by the clockwise 4, 4'-bipyridine (bpy) pillar linker rotation. The pillar rotation leads to the enlarged pore volume, rendering additional adsorption sites, which are not present in the pristine structure. In situ synchrotron PXRD experiments for C2 H4 and C2 H6 adsorption on CPL-2 confirmed the occurrence of pore expansion in CPL-2 MOF. The combined experimental and simulation study shows for the first time that the linker rotation in CPL-2 can result in a adsorption isotherm without hysteresis. This work developed a real insight into the nature of pillared-layer MOFs, and the revealed structural changes could be potentially exploited to enhance alkene and alkane working capacities of such microporous materials.