NMR relaxation and exchange in metal-organic frameworks for surface area screening

Journal Article · Sun Mar 15 00:00:00 EDT 2015 · Microporous and Mesoporous Materials

DOI:https://doi.org/10.1016/j.micromeso.2014.07.037· OSTI ID:1211090

Chen, JJ; Mason, JA; Bloch, ED; Gygi, D; Long, JR; Reimer, JA

We describe a robust screening technique that correlates the surface area of metal organic frameworks to the proton T-2 relaxation behavior of imbibed solvent at low field (13 MHz). In frameworks with small pore sizes (<1 nm) or strong solvent-framework interactions, diffusional exchange between the pore-confined and inter-particle solvent populations remains slow compared to the T-2 of the pore-confined solvent, allowing for a direct porosity analysis of the T-2 spectrum obtained from Laplace inversions. Increases in framework pore-size (>1 nm) lead to corresponding increases in the rate of solvent exchange, as confirmed by T-2 relaxation exchange (REXSY) experiments; increases in the pore size also increases the T-2 of the pore-confined solvent. The combination of these two effects results in comparable rates of relaxation and exchange, which precludes the direct analysis of Laplace inversions. Thus, two- and three-site kinetics models were applied to extract porosity from relaxation decays, thereby improving the utility of the porosity screening tool. (C) 2014 Elsevier Inc. All rights reserved.

• Sponsoring Organization: USDOE Advanced Research Projects Agency - Energy (ARPA-E)
• DOE Contract Number: DE- AR0000103
• OSTI ID: 1211090
• Journal Information: Microporous and Mesoporous Materials, Vol. 205; ISSN 1387-1811
• Country of Publication: United States
• Language: English