Abstract
Structural changes in ZIFs upon adsorption remain a paradigm due to the sensitivity of the adsorption mechanism to the nature of the organic ligands and gas probe molecules. Synchrotron X-ray diffraction under operando conditions clearly demonstrates for the first time that ZIF-4 exhibits a structural reorientation from a narrow-pore (np) to a new expanded-pore (ep) structure upon N2 adsorption, while it does not do so for CO2 adsorption. The existence of an expanded-pore structure of ZIF-4 has also been predicted by molecular simulations. In simulations the expanded structure was stabilized by entropy at high temperatures and by strong adsorption of N2 at low temperatures. These results are in perfect agreement with manometric adsorption measurements for N2 at 77 K that show the threshold pressure for breathing at ∼30 kPa. Inelastic neutron scattering (INS) measurements show that CO2 is also able to promote structural changes but, in this specific case, only at cryogenic temperatures (5 K).
Original language | English |
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Pages (from-to) | 14552-14558 |
Number of pages | 7 |
Journal | Journal of Materials Chemistry A |
Volume | 7 |
Issue number | 24 |
DOIs | |
State | Published - 2019 |
Externally published | Yes |
Funding
The authors would like to acknowledge nancial support from the MINECO (MAT2016-80285-p), Generalitat Valenciana (PROMETEOII/2014/004), H2020 (MSCA-RISE-2016/NanoMed Project), Spanish ALBA synchrotron (Projects AV-2017021985 and IH-2018012591) and Oak Ridge beam time availability (Project IPTS-20843.1). JSA and JGL acknowledge nancial support from UA (ACIE17-15) to cover all the expenses for INS measurements at Oak Ridge. JGL acknowledges GV (GRISOLIAP/2016/089) for the research contract. The computing resources were made available through the VirtuES and the ICE-MAN projects, funded by the Laboratory Directed Research and Development program at ORNL.
Funders | Funder number |
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Oak Ridge National Laboratory | |
Laboratory Directed Research and Development | |
Horizon 2020 Framework Programme | AV-2017021985, MSCA-RISE-2016, IH-2018012591, 734641, IPTS-20843.1, GRISOLIAP/2016/089 |
Ministerio de Economía y Competitividad | |
Generalitat Valenciana | PROMETEOII/2014/004 |