Unique thermal contraction of zeolite-templated carbons enabling micropore size tailoring and its effects on methane storage

Abstract

Zeolite-templated carbons (ZTCs) were prepared by the carbon replication of two different zeolite structures, i.e., BEA and FAU. We demonstrated that the micropore size of the ZTCs could be systematically controlled via post-synthesis thermal contraction. The thermal contraction was the unique feature of ZTCs, which was not observed with conventional activated carbons. The ZTCs had extra-high H contents on the abundant carbon edge sites because of their 3-dimensionally connected graphene nanoribbon structure. Thermal treatment in the absence of zeolite templates induced further dehydrogenation and densification of carbon framework, which caused such structural contraction. The ZTCs with tailored micropore sizes (1.1-1.5 nm) were used to study the effects of microporous structures on CH4 adsorption. Notably, the ZTCs with micropores smaller than 1.3 nm showed abnormal increases in the isosteric heat of adsorption with increasing CH4 coverage. This strongly indicated the presence of substantial lateral interactions between the adsorbates within these uniform micropores. The ZTC prepared from BEA zeolite and subsequently treated at 873 K showed the most promising volumetric CH4 storage capacity (210 cm(STP)(3)cm(-3)) and working capacity (175 cm(STP)(3) cm(-3)) at 5-65 bar due to its optimum microporous structures and uniform particle morphology enabling efficient particle packing. (C) 2018 Elsevier Ltd. All rights reserved.