**3.2 Interlayer expansion with large-sized silane agents assisted by deconstruction-reconstruction**

Although the simple high-temperature acid treatment is able to give interlayerexpanded structures, the assistant of silane agents helps the formation of more ordered and stable structures [69, 70]. The interlayer space of most lamellar precursors is large enough for monomolecular silane agent to insert two additional Si atoms in the pore window. To introduce more Si atoms and construct larger interlayer pore structures, the interlayer silylation achieved by large-sized silane molecules should be performed over the swollen intermediate [71, 72]. However, the conventional swelling process under the basic condition induces severe amorphization of the layer structures. To tailor the interlayer space, an interlayer deconstruction-reconstruction strategy was proposed by Wu et al. [73]. The PLS-3 lamellar precursor was firstly deconstructed by a mild acid treatment to induce the partial removal of SDA molecules and then reconstructed in the aqueous solution

**Figure 7.**

*Single-step delamination of MWW-layered zeolite via the isomorphous substitution of Al for B.*

**83**

**Figure 8.**

*New Trends in Layered Zeolites*

structure refinement.

*DOI: http://dx.doi.org/10.5772/intechopen.86696*

expanded by monomolecular silane agent.

containing bulky ammonium molecules, resulting in a lamellar precursor ECNU-9(P) with an enlarged interlayer space (**Figure 8**). The bulky ammonium molecules are the classical SDA for the PREFER-layered zeolite having the same layer structure as PLS-3. Thus, the layer structure of PLS-3 was well-protected in the reconstruction process. The interlayer-expanded ECNU-9 zeolite with large/extra-large pore system of 14 × 12-R was synthesized by the intercalation of a bulky single four ring-shaped silane agent into ECNU-9(P). Ti-ECNU-9, obtained by incorporating Ti atoms into ECNU-9 via H2TiF6 treatment, exhibited significantly high activity in the epoxidation reaction of cyclohexene, compared with 3D Ti-FER and the one

A similar strategy was also reported in the silylation of HUS-2-layered zeolite [74]. A distance of a half unit cell along [001] the direction for the up-and-down silanols on the layer surface and the presence of silicon vacancy induced the structural collapse of HUS-2 upon calcination [28]. Thus, a dimeric silane agent with two active groups attached to each silicon atom was applied to connect the relative long-distance up-and-down silanols and simultaneously fill the vacancy. The original HUS-2 lamellar zeolite could not offer enough interlayer space to accommodate the bulky dimeric silane agent. Thus, a Sub-HUS-2 material with interlayer deconstructed structure was firstly prepared and then reconstructed with the assistance of bulky ammonium molecules, resulting in an enlarged interlayer space for the following silylation. The obtained interlayer-expanded ECNU-19 zeolite with intersecting 12 × 8-R pore system was confirmed by the

*Scheme description of interlayer-expanded ECNU-9 zeolite via deconstruction-reconstruction strategy.*

### *New Trends in Layered Zeolites DOI: http://dx.doi.org/10.5772/intechopen.86696*

*Zeolites - New Challenges*

area (133 *vs* 53 m2

A more simple and mild delamination strategy without surfactant molecules and sonication was also proposed by Zones and Katz via the isomorphous substitution of Al for B in the B-containing MWW zeolite using aqueous Al(NO3)3 solution (**Figure 7**) [67]. The presence of neutral amine SDA and the careful control of temperature were proved to be critical for the success of this one-step delamination process. The obtained delaminated Al-containing ERB-1-del showed a similar morphology of single thin layers as the conventional delaminated ITQ-2 material and showed higher activity in Friedel-Crafts acylation reactions involving bulky substrates compared to 3D ERB-1C zeolite, due to the enhanced external surface

ERB-1 lamellar precursor with warm Zn(NO3)2 solution with a pH value of ~1 [68]. However, the one-step mild delamination strategy is now restricted to ERB-1 lamel-

Although the simple high-temperature acid treatment is able to give interlayerexpanded structures, the assistant of silane agents helps the formation of more ordered and stable structures [69, 70]. The interlayer space of most lamellar precursors is large enough for monomolecular silane agent to insert two additional Si atoms in the pore window. To introduce more Si atoms and construct larger interlayer pore structures, the interlayer silylation achieved by large-sized silane molecules should be performed over the swollen intermediate [71, 72]. However, the conventional swelling process under the basic condition induces severe amorphization of the layer structures. To tailor the interlayer space, an interlayer deconstruction-reconstruction strategy was proposed by Wu et al. [73]. The PLS-3 lamellar precursor was firstly deconstructed by a mild acid treatment to induce the partial removal of SDA molecules and then reconstructed in the aqueous solution

lar precursor and has its limitations in the general application.

**deconstruction-reconstruction**

**3.2 Interlayer expansion with large-sized silane agents assisted by** 

*Single-step delamination of MWW-layered zeolite via the isomorphous substitution of Al for B.*

/g). An all-silica analog of ERB-1-del can be obtained by treating

**82**

**Figure 7.**

containing bulky ammonium molecules, resulting in a lamellar precursor ECNU-9(P) with an enlarged interlayer space (**Figure 8**). The bulky ammonium molecules are the classical SDA for the PREFER-layered zeolite having the same layer structure as PLS-3. Thus, the layer structure of PLS-3 was well-protected in the reconstruction process. The interlayer-expanded ECNU-9 zeolite with large/extra-large pore system of 14 × 12-R was synthesized by the intercalation of a bulky single four ring-shaped silane agent into ECNU-9(P). Ti-ECNU-9, obtained by incorporating Ti atoms into ECNU-9 via H2TiF6 treatment, exhibited significantly high activity in the epoxidation reaction of cyclohexene, compared with 3D Ti-FER and the one expanded by monomolecular silane agent.

A similar strategy was also reported in the silylation of HUS-2-layered zeolite [74]. A distance of a half unit cell along [001] the direction for the up-and-down silanols on the layer surface and the presence of silicon vacancy induced the structural collapse of HUS-2 upon calcination [28]. Thus, a dimeric silane agent with two active groups attached to each silicon atom was applied to connect the relative long-distance up-and-down silanols and simultaneously fill the vacancy. The original HUS-2 lamellar zeolite could not offer enough interlayer space to accommodate the bulky dimeric silane agent. Thus, a Sub-HUS-2 material with interlayer deconstructed structure was firstly prepared and then reconstructed with the assistance of bulky ammonium molecules, resulting in an enlarged interlayer space for the following silylation. The obtained interlayer-expanded ECNU-19 zeolite with intersecting 12 × 8-R pore system was confirmed by the structure refinement.

**Figure 8.** *Scheme description of interlayer-expanded ECNU-9 zeolite via deconstruction-reconstruction strategy.*
