Intrinsic flexibility of the zeolitic imidazolate framework ZIF-7 unveiled by CO₂ adsorption and Hg intrusion.
ZIF-7, built as an assembly of Zn(II) centers and benzimidazolate ligands, shows prominent S-shaped isotherms upon CO2 adsorption that can be attributed to sorbate-induced gate-opening phenomena involving a narrow-to-large pore phase transition. This peculiar sorption pattern can be captured via the formulation of thermodynamic isotherms, providing a direct enthalpic and entropic view of the gate-opening process. Relying on such an approach, an energy barrier with preferential enthalpic nature for CO2 adsorption/desorption in the gate-opening region could be unveiled. Moreover, the elastic energy involved during the gate-opening process was revisited to 1.4-2.8 kJ mol(-1) of solid in the temperature range 273-323 K, matching the value measured by isostatic compression of a ZIF-7_lp sample filled with DMF and showing a dominant entropic contribution.
Eco-Efficient Products and Processes Laboratory (E2P2L), UMI 3464 CNRS/Solvay, 3966 Jin Du Road, Xin Zhuang Industrial Zone, 201108 Shanghai (China); University of Lyon, Institut de Recherches sur la Catalyse et l'Environnement de Lyon (IRCELYON), UMR 5256 CNRS/UCBL1, 2 Av. Albert Einstein, 69626 Villeurbanne (France). marc.pera-titus-ext@solvay.com.
Marc
M
Pera-Titus
CO2; compression; gate opening; thermodynamic isotherm; zeolitic imidazolate framework