An Overview of the Challenges and Progress of Synthesis, Characterization and Applications of Plugged SBA-15 Materials for Heterogeneous Catalysis

Abstract

A new generation of SBA-15, plugged SBA-15, was initially synthesized in 2002 using extra silica precursors (Si/organic template molar ratios ≈ 80–140) in the gel mixture. The plugged SBA-15 materials possess short cylinders (length ≈ 20–100 nm), which are connected to neighbors by constricted entrances (windows) through the central axis. The gas adsorption–desorption isotherms of plugged SBA-15 materials present unique hysteresis loop Type H5 classification identified by IUPAC in 2015, which is related to certain pore structures containing open and plugged mesopores. The plugged SBA-15 has been used to support various types of catalysts, including metal complexes, metal nanocatalysts, and active metals by the incorporation in their framework demonstrating excellent (enantio)selectivity, stability against coke, and thermal stability. The plugged SBA-15 materials bear the other unique properties of the ship-in-the-bottle synthesis of, e.g., metal complexes that confine homogeneous catalysts, which is not possible by conventional SBA-15 due to leaching. In this mini-review, the challenges and progress of the synthesis in controlling the plugging and incorporation of metals and organic moiety in their framework, characterizing the short mesochannel dimensions (window and length sizes) by several advanced techniques and applying plugged SBA-15 materials in heterogeneous catalysis for challenging reactions, has been discussed.

Recent developments in state-of-the-art silica-modified catalysts for the fixation of CO2 in epoxides to form organic carbonates

“…Furthermore, it can be functionalized with diverse metal oxides (active phase of the catalyst), resulting in high thermal and hydrothermal stability. 155–161 In addition, it exhibits great potential as a support for the active phase of heterogeneous catalysts and results in easy diffusion due to the minimum obstruction by the adjustment of its pore diameter. 162 In the preceding section, different DFNS- and MCM-41-modified catalysts for CO 2 fixation reactions were summarized.…”

Preparation of Amphiphilic Chitosan-Loaded Bentonite Adsorbent and Its Performance in Removing Organic Matter from Coking Wastewater

“…It can be seen from Figure 5 a–c that these adsorbents contain a certain number of mesopores since their N 2 adsorption–desorption isotherms show a hysteresis loop [ 25 ]. According to hysteresis loop classification proposed by the International Union of Pure and Applied Chemistry (IUPAC), the hysteresis loop types of BT, CTS–BT, and C18CTS–BT belong to the H3 type [ 26 ]. Based on the Brunner–Emmet–Teller (BET) method, the specific surface areas of BT, CTS–BT, and C18CTS–BT are determined to be 34.63 m²·g −1 , 49.87 m²·g −1 , and 51.93 m²·g −1 , respectively.…”

Periodic Mesoporous Organosilica Nanomaterials with Unconventional Structures and Properties

“…Furthermore, leaching of the immobilized catalyst from the pores could dramatically be reduced thanks to the sterical hindrance of the “tight interior”. The effect of the reaction conditions for plug formation in PMOs is less developed compared to the plugged mesoporous materials such as SBA‐15 [34a] and future efforts in other research should address this issue. The same effort should also be made for new synthetic strategies of helical PMOs by employing the synthetic experiences for the preparation of mesoporous materials [56] …”

“…In contrast, PMOs with partially plugged pores have found some applications for the selective adsorption of macromolecules [35] as well as in asymmetric organic synthesis by improving the chiral induction in the confined spaces of the plugged material [36] . However, synthesis and applications of plugged PMOs are not suitably developed compared to other mesoporous silica such as SBA‐15 [34a] …”