Correspondence Fabrication of molecular-sieve-type carbons from Salix viminalis Jerzy P. Lukaszewicz * , Radosław P. Wesołowski Faculty of Chemistry, Nicholas Copernicus University, 87-100 Torun, Poland article info Article history: Received 9 December 2007 Received in revised form 13 April 2008 Accepted 22 April 2008 Available online 25 May 2008 Keywords: Porosity Carbon molecular sieves Carbonization Salix viminalis abstract The discovery of a novel raw material for the fabrication of strictly nanoporous carbons is described. The invention deals with the application of widely accessible wood from Salix viminalis as a precursor for car- bonization. High temperature carbonization intermediately yields carbons of very narrowed pore size distribution (PSD) in the range below 1 nm. Regarding narrowed PSD the carbons may be considered in future as an effective molecular sieves for gas separation. The determined effective pore dimension is similar to the inner diameter of opened carbon nanotubes which size is essential in other applications like gas (hydrogen) storage. Estimated production cost of the production of nanoporous carbons is several orders lower than for carbon nanotubes. Ó 2008 Elsevier Inc. All rights reserved. 1. Introduction Molecular sieves (MS) are often defined as carbonaceous mate- rials possessing narrowed pore sizes distribution [1]. The men- tioned existence of ‘‘tinny” and uniform pores in a solid is the main factor distinguishing MS from other porous solids. According to some researchers, the term MS (carbon molecular sieves CMS, too) should be applied to adsorbents exhibiting molecular sieving effect in practice [2]. Because of the effect, CMS are widely applied for gas separation [3,4], mixture purification or catalytic processes [5]. The phenomenon of selective adsorption depends not only on the size of pores, but also on other properties of CMS, such as shape of pores and/or electron properties of CMS. Unlike the other known molecular sieving materials of mineral character [6], CMSs posses adequate chemical (pH) and thermal (in inert atmosphere) stability and high hydrophobicity (if not chem- ically modified). Number of procedures and precursors for prepar- ing CMS have been proposed and developed since the discovery of molecular sieving effect of Saran char in the late 1940s [7]. More recently, highly-ordered mesoporous materials, like zeolites or MCM-48 silicas, have been found convenient to use as templates for the preparation of mesoporous CMS. In such a matrix, car- bon-containing precursor is placed inside and then carbonized, for instance sucrose in MCM-48 [8], divinylbenzene in MCM-48 [9], or furfuryl alcohol in bentonite and taeniolite [10]. However, the application of proposed methods in mass production of CMSs remains complicated as consisted of several steps and requiring hazardous reagents. Also the yield of the fabrication method seems to be rather low and therefore the whole method is hardly trans- ferable to industrial scale. One may also obtain specific carbon structures of relatively uni- form pore size distribution by the deposition of a carbon precursor into the existing pore system. Some methods reported in literature, exploited chemical vapor deposition of coal tar pitch [11], poly- furfuryl alcohol [12], or benzene [13], into the pores of activated carbon. Also in this case, the fabrication is rather complicated and limited to laboratory scale. Nearly the same shortcomings deal with fabrication of carbon nanotubes (CNTs). In general, after opening and fragmentation, CNTs might be regarded as a carbon-type adsorbent of narrowed PSD due to the frequently reported, uniform inner diameter of the opened tubes [14]. Additionally, in some cases the uniform spaces between aligned CNTs can contribute to the total pore vol- ume of such samples [15]. Narrowed PSD can be observed also for some active carbons obtained by the usual carbonization/activa- tion procedure of some sorts of natural and/or synthetic precur- sors. Such a narrowed PSDs were mentioned for active carbons for which preparation starting materials like wood shells, as of walnut [16], or palm fruits [17], were used. The announcements claim the such fabricated active carbons to posses pore structure typical for molecular sieves but in many cases the determined PSD is not narrowed and therefore being far from the ideal one and one may find that pores of differentiated size contribute con- siderably to the total pore volume [18]. Regarding the mentioned applications of solids of narrowed PSD (including CMSs) and the shortcomings of some already discovered CMS fabrication routes, one has to state that there is an obvious need for an inexpensive carbon-type adsorbent in which pores are really uniform and their size is around 1 nm. This paper reports 1387-1811/$ - see front matter Ó 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.micromeso.2008.04.034 * Corresponding author. Tel.: +48 60 5314300. E-mail address: lukaszju@chem.uni.torun.pl (J.P. Lukaszewicz). Microporous and Mesoporous Materials 116 (2008) 723–726 Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso