Tuning of Gate Opening of an Elastic Layered Structure MOF in CO2 Sorption with a Trace of Alcohol Molecules

Abstract

It is important to tune the sorption behavior of metal-organic framework (MOF) materials. Ethanol treatment on the hydrated form of [Cu(bpy)(2)(BF(4))(2)], which is a representative flexible MOF showing the fascinating gate phenomenon on CO(2) sorption, induces an easier dehydration and a significant decrease in the CO(2) gate pressure. The results of IR, X-ray diffraction (XRD), and X-ray absorption fine structure (XAFS) measurements indicated that water molecules in the lattice of the hydrated form can be removed even at room temperature after the ethanol treatment and the basic 2D layered structure remains with a slight interlayer expansion. The results of thermogravimetric (TG) and gas chromatograph/mass spectrometry (GC/MS) analyses and of CO(2) sorptions indicated that the change of the gate phenomenon was caused by a trace of residual ethanol molecules included in the structure. Similar phenomena were observed on alcohols with different polarity and molecular size.