Formaldehyde encapsulated in lithium-decorated metal-organic frameworks: a density functional theory study.
The stability of monomeric formaldehyde encapsulated in the lithium-decorated metal-organic framework Li-MOF-5 was investigated by means of density functional calculations with the M06-L functional and the 6-31G(d,p) basis set. To assess the efficiency of Li-MOF-5 for formaldehyde preservation, we consider the reaction kinetics and the thermodynamic equilibrium between formaldehyde and its trimerized product, 1,3,5-trioxane. We propose that trimerization of encapsulated formaldehyde takes place in a single reaction step with an activation energy of 34.5 kcal  mol(-1). This is 17.2 kcal  mol(-1) higher than the corresponding activation energy in the bare system. In addition, the reaction energy of the system studied herein is endothermic by 6.1 kcal  mol(-1) and the Gibbs free energy (ΔG) of the reaction becomes positive (11.0 kcal  mol(-1)). Consequently, the predicted reverse rate for the trimerization reaction in the Li-MOF-5 is significantly faster than the forward rate. The calculations show that the oligomerization of formaldehyde in Li-MOF-5 is a reversible reaction, suggesting that such a zeolite might be a good candidate material for preserving formaldehyde in its monomeric form.
Laboratory for Computational and Applied Chemistry, Department of Chemistry, Faculty of Science and Center of Nanotechnology, Research and Development Institute, Kasetsart University, Bangkok 10900, Thailand.
Thana
T
Maihom
Saowapak
S
Choomwattana
Pipat
P
Khongpracha
Michael
M
Probst
Jumras
J
Limtrakul