A CVD route for the preparation of templated and activated carbons for gas storage applications using zeolitic imidazolate frameworks (ZIFs) as template

Abstract

Templated porous carbon materials were prepared via a chemical vapour deposition (CVD) method using zeolitic imidazolate framework (ZIF) templates impregnated with furfuryl alcohol (FA). ZIF-templated carbons prepared at CVD temperature of between 700 and 850°C are highly microporous and exhibit surface area in the 350–970m2/g range (with up to 96% from micropores) and pore volume of between 0.28 and 0.66cm3/g. After chemical activation (with KOH) the surface area and pore volume increase significantly to as high as 2400m2/g and 1.6cm3/g, respectively. This increase in porosity is accompanied by a broadening of the micropore size distribution and formation of larger pores, although the activated carbons remain predominantly microporous. The increase in textural properties after activation is reflected in enhancement of hydrogen storage capacity; activated ZIF-templated carbons prepared at CVD temperature of 700 and 850°C achieve high hydrogen uptake (at 20bar and −196°C) of 6.2 and 5.1wt%, respectively. Activation also improves the CO2 uptake; the CO2 storage capacity (at 25°C and 1bar under flow conditions) increases from ca. 1.8mmol/g for ZIF-templated carbons to as high as 2.4mmol/g after activation. The best porosity and gas uptake properties were achieved by a sample whose preparation required temperatures no higher than 700°C. Our findings show that incorporation of a CVD step not only simplifies the templating process by reducing the temperature required but also removes the need for a washing step prior to activation.