# Tunable Effect of the Calcination of the Silanol Groups of KIT-6 and SBA-15 Mesoporous Materials
## 1 Introduction  
According to the IUPAC (International Union of Pure and Applied Chemistry), porous materials can be grouped into three distinct categories according to their porosities [1]. Materials with pores smaller than 2 nm are classified as microporous, those with pores larger than 50 nm are called macroporous, and those with intermediate pore sizes are mesoporous [2]. In the early 1990s, Mobil Oil Corporation researchers published the first syntheses of mesoporous materials (M41S), which were manufactured using an alkyltriethylammonium halide as a template in an alkaline medium [3; 4]. These new compounds presented very characteristic and peculiar properties, such as a high specific surface area (up to 1400 m\({}^{2}\) g\({}^{-1}\)), a pore volume greater than 0.5 cm\({}^{3}\) g\({}^{-1}\) and narrowly distributed cylindrical pores (2-30 nm) [5]. The physicochemical properties of these compounds have been tested and evaluated by many researchers [6; 7; 8; 9; 10; 11; 12]. In 1998, the syntheses of a group of mesoporous materials called SBA, using an organic copolymer (mainly PEO-PPO-PEO) as a template in an acid medium, were published [13; 14]. In this family of compounds, the best known is SBA-15, which is a highly ordered two-dimensional hexagonal (_P6 nm_) thick-walled silica (3 to 6 nm) mesostructured material with uniform, large, adjustable pores up to 30 nm in diameter and high thermal and hydrothermal stability due to the presence of mesoporous interconnected micropores [13]. In 2003, the synthesis of a new mesoporous material called KIT-6 was first published [15]. This material was manufactured in a manner very similar to that used in the production of the SBA-15 but using butanol-1 as a swelling agent. KIT-6 exhibits cubic _la3d_ symmetry with excellent thermal/hydrothermal stabilities and consists of two continuous and interpenetratingchiral channel systems interconnected in a three-dimensional open cylindrical mesoporous network [16]. It has a wall thickness between 4 and 6 nm [17], a specific area of up to 800 m\({}^{2}\) g\({}^{-1}\), and a high pore volume (up to 1.05 cm\({}^{3}\) g\({}^{-1}\)) with pore diameters in the range of 4 to 12 nm [15]. The main pores are interconnected with micropores up to 1.8 nm in diameter at specific points [18; 19]. With the discoveries of these two mesoporous nanosilica (MNS) materials, a wide range of possibilities has been opened for the application of both SBA-15 [20; 21; 22; 23; 24; 25; 26; 27; 28] and KIT-6 [29; 30; 31; 32; 33; 34; 35; 36; 37] in various areas, such as catalysis, adsorption, separation, drug release, optical devices, and sensors. The development of MNS has involved three distinct generations [38]. The first corresponded to the conceptual demonstration of MNS through the discovery of materials such as the M41S and SBA families. The second generation was characterized by the improvement and refinement of the study of these materials in terms of in vitro applications and in situ analysis. Finally, the third and current generation of studies functionalized MNS [39; 40]. Pure silica mesoporous materials have intrinsic limitations in both functionality and strength, and controlling the pore surface chemistry is critical to improving their applications [12]. The surface functionalization of these mesoporous compounds with organic and inorganic functional groups leads to the formation of materials with new physicochemical properties [41], which can be used in various areas, such as catalysis, adsorption, and separation [42; 43]. The formation of the materials SBA-15 and KIT-6 are made by the sol-gel process [44]. This is a traditional methodology based on the hydrolysis and condensation of metal alkoxides (TEOS) to produce colloidal particles (sol) that are converted into a lattice (gel) [45]. The conditions employed directly affect the properties of the materials produced.