Theoretical and experimental analysis of H2 binding in a prototype metal organic framework material

TL;DR

This paper combines experimental and theoretical methods to analyze hydrogen binding in a specific metal-organic framework, revealing binding site locations, energies, and vibrational shifts consistent with experimental data.

Contribution

It provides a detailed theoretical and experimental analysis of H2 binding sites and energies in Zn2(BDC)2(TED) MOF, using vdW-DF calculations and infrared spectroscopy.

Findings

Deepest H2 binding sites are within two narrow channels.

Binding energies and site counts match experimental adsorption data.

H-H stretch frequency shifts by approximately -30 cm-1 at strongest sites.

Abstract

Hydrogen adsorption by the metal organic framework (MOF) structure Zn2(BDC)2(TED) is investigated using a combination of experimental and theoretical methods. By use of the nonempirical van der Waals density-functional (vdW-DF) approach, it is found that the locus of deepest H2 binding positions lies within two types of narrow channel. The energies of the most stable binding sites, as well as the number of such binding sites, are consistent with the values obtained from experimental adsorption isotherms and heat of adsorption data. Calculations of the shift of the H-H stretch frequency when adsorbed in the MOF give a value of approximately -30 cm-1 at the strongest binding point in each of the two channels. Ambient temperature infrared absorption spectroscopy measurements give a hydrogen peak centered at 4120 cm-1, implying a shift consistent with the theoretical calculations.