TY - JOUR

T1 - Role of the metal cation in the dehydration of the microporous metal–organic frameworks CPO-27-M

AU - Rosnes, Mali H.

AU - Pato-Doldán, Breogán

AU - Johnsen, Rune E.

AU - Mundstock, Alexander

AU - Caro, Jürgen

AU - Dietzel, Pascal D.C.

N1 - Funding Information: The authors would like to thank Dr. Dmitry Chernyshov, Dr. Alexey Mikheykin, Dr. Vadim Diadkin, and Dr. Wouter van Beek at the Swiss–Norwegian Beamlines for their support in performing the experiments at the ESRF, and acknowledge the support from the Research Council of Norway through the FRINATEK Program (grant 221596 ), ISP-KJEMI Program (grant 209339 ) and SYNKNOYT (grants 227702 and 247734 ).

PY - 2020/12/15

Y1 - 2020/12/15

N2 - The dehydration of the CPO-27-M (M-MOF-74, M = Zn, Co, Ni, Mg, Mn, Cu) metal-organic framework series has been investigated comprehensively using in situ variable temperature powder X-ray diffraction (VT-PXRD) and thermal analysis (TG) coupled with mass spectrometry (MS). Significant differences in the order of water desorption from different adsorption sites on heating are found with varying metal cation in the otherwise isostructural material. For all CPO-27-M (except M = Cu), water is bonded significantly more strongly to the accessible open metal sites, and these water molecules are only desorbed at higher temperatures than the other water molecules. CPO-27-Cu is an exception, where all water molecules desorb simultaneously and at much lower temperatures (below 340 K). MS and TG data show that all CPO-27-M start to release traces of CO2 already at 300–350 K, and thus long before bulk thermal decomposition is observed. Only for CPO-27-Co, the CO2 release is essentially constant on its baseline between 450 and 700 K, and it is the only CPO-27-M member that shows a stable plateau in the TG in this region. Additional rehydration studies on CPO-27-Co show that the MOF incorporates any water molecules present until the pores are fully loaded. CPO-27-Co consequently behaves as an efficient trap for any water present.

AB - The dehydration of the CPO-27-M (M-MOF-74, M = Zn, Co, Ni, Mg, Mn, Cu) metal-organic framework series has been investigated comprehensively using in situ variable temperature powder X-ray diffraction (VT-PXRD) and thermal analysis (TG) coupled with mass spectrometry (MS). Significant differences in the order of water desorption from different adsorption sites on heating are found with varying metal cation in the otherwise isostructural material. For all CPO-27-M (except M = Cu), water is bonded significantly more strongly to the accessible open metal sites, and these water molecules are only desorbed at higher temperatures than the other water molecules. CPO-27-Cu is an exception, where all water molecules desorb simultaneously and at much lower temperatures (below 340 K). MS and TG data show that all CPO-27-M start to release traces of CO2 already at 300–350 K, and thus long before bulk thermal decomposition is observed. Only for CPO-27-Co, the CO2 release is essentially constant on its baseline between 450 and 700 K, and it is the only CPO-27-M member that shows a stable plateau in the TG in this region. Additional rehydration studies on CPO-27-Co show that the MOF incorporates any water molecules present until the pores are fully loaded. CPO-27-Co consequently behaves as an efficient trap for any water present.

KW - CPO-27-M

KW - Dehydration

KW - In situ techniques

KW - M-MOF-74

KW - Metal-organic frameworks

KW - Phase transitions

KW - Thermal analysis

KW - X-ray diffraction

UR - http://www.scopus.com/inward/record.url?scp=85090888800&partnerID=8YFLogxK

U2 - 10.1016/j.micromeso.2020.110503

DO - 10.1016/j.micromeso.2020.110503

M3 - Article

AN - SCOPUS:85090888800

VL - 309

JO - Microporous and Mesoporous Materials

JF - Microporous and Mesoporous Materials

SN - 1387-1811

M1 - 110503

ER -