Influence of Metal Substitution on the Pressure-Induced Phase Change in Flexible Zeolitic Imidazolate Frameworks

• DOI: 10.1021/jacs.8b09631
• Publication Date: 2018-11-07T18:43:55Z
• Authors: C. Michael McGuirk; Tomče Runčevski; Julia Oktawiec; Ari Turkiewicz; Mercedes K. Taylor; Jeffrey R. Long
• Keywords: Zeolitic imidazolate framework; Imidazolate

Metal-organic frameworks that display step-shaped adsorption profiles arising from discrete pressure-induced phase changes are promising materials for applications in both high-capacity gas storage and energy-efficient separations. The thorough investigation of such through chemical diversification, measurements, situ structural characterization is therefore crucial broadening their utility. We examine a series isoreticular, flexible zeolitic imidazolate (ZIFs) the type M(bim)2 (SOD; M = Zn (ZIF-7), Co (ZIF-9), Cd (CdIF-13); bim- benzimidazolate), elucidate effects metal substitution on pressure-responsive resulting CO2 CH4 step positions, pre-step uptakes, capacities. Using ZIF-7 as benchmark, we reexamine poorly understood transition responsible its steps and, high-pressure verify it displays isotherms. ZIF-9 material shown to undergo an analogous change, yielding with similar capacities ZIF-7, but shifted threshold pressures. Further, Cd2+ analogue CdIF-13 reported here first time, behavior distinct ZIF-9, negligible adsorption, ∼50% increase capacity, dramatically higher Remarkably, single-crystal-to-single-crystal change pore-gated also achieved CdIF-13, providing insight into yields these ZIFs. Finally, show endothermic provides intrinsic heat management during adsorption.