Ultramicroporous Carbon Synthesis Using Lithium-Ion Effect in ZSM‑5 Zeolite Template

Zeolite templating
is a versatile synthesis route to produce various
types of ordered microporous carbon. However, the synthesis thus so
far has been limited to the use of wide-pore zeolites with 12-membered
ring (12MR) pore mouths or more because of the diffusion limitation
of organic carbon precursors. Here, we report an extension of the
carbon synthesis to a 10MR zeolite, through acetylene carbonization
in Li+-ion-exchanged ZSM-5 zeolite. The promoting effect
of the Li+ ions on the carbon synthesis could be relevant
to the carbide-forming property of the element, similar to the recently
reported cases of La3+, Y3+, and Ca2+ cations in 12MR zeolites. The resultant carbon exhibited an ordered
array of ultramicropores of 0.5 nm diameter, which corresponded to
the thickness of the zeolite framework. Because of the ultramicroporosity,
the ZSM-5-templated carbon exhibited an anomalously high value of
surface-area-normalized electrical double-layer capacitance.