Microporous and Mesoporous Materials 25 (1998) 75–80 Stepwise functionalization of mesoporous crystalline silica materials Man Park, Sridhar Komarneni * Materials Research Laboratory, The Pennsylvania State University, University Park, 16802 PA, USA Received 17 November 1997; received in revised form 23 April 1998; accepted 1 May 1998 Abstract Novel properties have been achieved in mesoporous crystalline silica materials by organic functionalization. In this study, localized functionalization and bifunctionalization of silica MCM-41 was attempted through the stepwise post- synthesis silylation. When MCM-41 was treated with various silylating agents for 6 hours before template removal, change in pore size only was observed without any change in surface area and pore volume. MCM-41 was difunctionalized with both decyl groups on edges of pores and methyl groups on inner surfaces of pores. Capillary condensation of water took place at higher relative pressure in MCM-41 with decyl groups on edges than in unsilylated MCM-41, whereas hydrophobic property was observed in MCM-41 which were difunctionalized with decyl groups on edges of pores and with methyl groups on inner surfaces of pores. This study shows that the manipulation of pore size and functionality with/without any change in surface area and pore volume and the combination of two different functionalities could be achieved in MCM-41 through the stepwise functionalization. © 1998 Elsevier Science B.V. All rights reserved. Keywords: MCM-41; Stepwise functionalization; Bifunctionalization; Textural property 1. Introduction to realize their great potential in a wide range of industrial, environmental, and agricultural applications. Mesoporous crystalline materials, MCM-41 Quite recently, organic functionalization of (hexagonal symmetry) and MCM-48 (cubic sym- mesoporous crystalline silica materials is receiving metry), exhibit extremely high surface area and a great deal of attention due to the novel properties well defined pore size as well as high thermal of functionalized silica MCM-41 [9–15]. Silica stability and flexible framework composition [1]. MCM-41 can be organically functionalized either Since their discovery in 1991–2 [2], intensive efforts through direct synthesis [10,11] from the mixture have been devoted to the development of synthesis of an organic-substituted silicon alkoxide and techniques [3–5], framework modification [1,3,6– tetraalkoxysilane or through post-synthesis silyla- 8] and surface functionalization [1,9–15] in order tion [9–13] using an organic-substituted silicon alkoxide. Up to date, a number of silica MCM-41 have been successfully functionalized for various * Corresponding author. Tel: +1 814 865 1542; Fax: +1 814 865 2326; E-mail: sxk1@alpha.mrl.psu.ed purposes. However, both methods not only lead 1387-1811/98/$ – see front matter © 1998 Elsevier Science B.V. All rights reserved. PII: S1387-1811(98)00173-5