Evaluation of copper-1,3,5-benzenetricarboxylate metal-organic framework (Cu-MOF) as a selective sorbent for Lewis-base analytes

The metal-organic framework copper-1,3,5-benzenetricarboxylate (Cu-BTC) was evaluated for its ability to selectively interact with Lewis-base analytes by examining retention on gas-chromatographic columns packed with Chromosorb W HP that contained 3.0% SE-30 along with various loadings of Cu-BTC. Scanning electron microscopy images of the support material showed the characteristic Cu-BTC crystals embedded in the SE-30 coating on the diatomaceous support. The results indicated that the Cu-BTC-containing stationary phase had limited thermal stability (220 °C) and strong general retention for analytes. Kováts index calculations showed selective retention (amounting to about 300 Kováts units) relative to n-alkanes for many small Lewis-base analytes on a column that contained 0.75% Cu-BTC compared with an SE-30 control. Short columns that contained lower loadings of Cu-BTC (0.10%) allowed elution of nitroaromatics; however, selectivity was not observed for aromatic compounds (including nitroaromatics) or nitroalkanes. Observed retention characteristics are discussed.