Intercalation and Oligomerization of Organic Molecules in the Interlayer Nanospace of Alkali Metal-Graphite Intercalation Compounds

Abstract

Intercalation of organic molecules into alkali metal (AM)-graphite intercalation compounds (GIC) and their secondary reactions, such as oligomerization, in the interlayer space are reviewed.Some aromatic molecules such as benzene and tetrahydrofuran (THF) have been known to be intercalated to AM-GICs, resulting ternary GICs. It has been proven that benzene molecules intercalated in the GICs oligomerize slowly in the interlayer nanospace, probably under the catalytic effect of Cs+ ion.On the other hand, aliphatic hydrocarbons have been known to be physintercalated to stage 2 AM-GICs, in particular CsC24. Among aliphatic hydrocarbons, ethylene and acethylene, which have a double or triple bond, showed unusual behavior: Contrary to usual physintercalation, the temary GICs of C2H4 and C2H2 with CsC24 were found to be very stable even in air. Further investigations on the C2H4 temary GIC, by using XRD, chemical analysis/MS, calorimetry etc., have revealed that the observed unusual stability is caused by the oligomerization of C2H4 molecules in the interlayer nanospace. In contrast to other organic molecule-temary GICs, the intercalation of C2H4 molecules into CsC24 gives very little effect in its electrical conductivity, indicating that the backdonation of conduction electrons from graphene layers isrelatively small.The possible secondary reaction of intercalated molecules, in particular oligomerization or polymerization, will give a vast prospects in obtaining new functional GICs with high electrical conductivity and stability.