## 3 MWW-Type Materials by Post-Synthesis Modifications  
(P)MCM-22 offers diverse possibilities to obtain more open structures. The first example of this is the interlayer expanded zeolite called IZ-MWW, in which silanol groups of the LZP were reacted with alkoxysilanes such as SiMe\({}_{2}\)Cl\({}_{2}\) or Si(EtO)\({}_{2}\)Me\({}_{2}\)[43]. After calcination, a 12-ring pore was formed by the single silicon atoms that act as small pillars, as represented in Figure 4. The increase in pore structure may serve catalytic purposes to diffuse large molecules and as selective adsorbents for adsorption and separation. The successful swelling procedure is a key step to obtain a hybrid organic-inorganic material used to form pillared and delaminated materials with high accessibility. In contrast, this procedure is still challenging (cost- and time-consuming and with the possible formation of competing mesophases). The separation of individual MWW lamellae was carried out using long alkyl organic molecules (hexadecyltrimethylammonium cations, CTA\({}^{+}\), usually) to populate the interlamellar region. An alkaline media was needed to deprotonate the silanol groups and break the hydrogen bonds between the lamellae. Tetrapropylammonium hydroxide is a double agent because it supplies hydroxide ions and its counter ion (TPA\({}^{+}\)) to facilitate the entering of the CTA\({}^{+}\) molecules into the interlamellar region. When NaOH is used, the small Na\({}^{+}\) cations rapidly enter the interlamellar region and compensate negatively charged ions before populating the CTA\({}^{+}\) molecules in the interlamellar region, resulting in an unsuccessfully or partially swollen material [44]. Several studies have sought to better understand swollen materials using different swelling conditions (room temperature or 80 \({}^{\circ}\)C), molecular dimensions of swelling agents, hydroxide sources, and strategies of recycling and reusing the swelling solution [45; 46; 47; 48; 49; 50]. MCM-36 was the first pillared molecular sieve with zeolite properties. The swollen precursor was mixed with a pillaring agent (TEOS) and went through subsequent calcination where rigid silica pillarsformed, keeping the individual MWW lamella separated from each other. Characterization results showed a surface area of 896 m\({}^{2}\cdot\)g\({}^{-1}\) (compared with 400 m\({}^{2}\cdot\)g\({}^{-1}\) for MCM-22) with mesopores between 2 and 4 nm and higher adsorption capacities of bulky molecules as 1,3,5-trimethylbenzene (TMB) with 0.040 mg\(\cdot\)g\({}^{-1}\), whereas MCM-22 showed negligible adsorption [51; 52]. Another important pillared material was reported, but in this case, aryl silsesquioxane molecules acted as organic pillars between MWW lamellae to obtain a multifunctional organic-inorganic catalytic material with a hierarchical structure [53]. The swollen precursor was reacted with a solution of 1,4-bis(triethoxysilyl)benzene (BTEB) and the CTA\({}^{+}\) molecules were removed by acid extraction. Following this, amino groups were incorporated onto the bridged benzene groups in the interlayer space. The obtained materials showed acid sites provided by the MWW structure of lamellae combined with basic sites from amino groups incorporated on the aryl molecules. Characterization results showed a basal spacing of 4.1 nm, a surface area of 556 m\({}^{2}\cdot\)g\({}^{-1}\), and a mesoporous region formed by the separated lamellae. The use of swollen MWW materials treated with ultrasound and acidic medium and a posterior calcination generate ITQ-2, the first delaminated zeolite [54]. Its surface area showed 700 m\({}^{2}\cdot\)g\({}^{-1}\) and a broad distribution of mesopores due to the random stacking of MWW lamellae in edge-to-face orientation, as shown in Figure 4. ITQ-2 had superior capacities (7 times higher than MCM-22) for the adsorption of TMB and superior catalytic performance for reactions with the cracking of bulky molecules, such as 1,3-disopropylbenzene and vacuum gas oil in gasoline and diesel [55].