Review on Template Removal Techniques for Synthesis of Mesoporous Silica Materials

Abstract

The key step in the preparation of mesoporous silica materials is the removal of organic templates occluded inside the pores including nonionic, cationic, anionic surfactants and even ionic liquid (IL). The most common method to remove templates is conventional calcination under air at 550 °C. Although templates can be completely removed from the pores, calcination suffers many serious drawbacks including significant framework shrinkage, the collapse of the ordered structure, reduction of silanol concentrations on the pore wall (which are of high importance for postmodification), generation of large amounts of CO 2 and organic amine compounds, the presence of carbon deposits or coke as a contaminant, elimination of organic functionalities (such as organoalkoxysilanes with amino groups), and the inability to recover or reuse expensive organic templates. That is why many attempts have been reported in the literature to develop novel methods for removing organic templates that are favorable from both economic and environmental standpoints for potentially large-scale applications. The current study reviews the recent development methods for template removal from various types of mesoporous silica materials. We have divided the template removal approaches into two categories: physical method and chemical method. The effects of those methods are discussed in detail on the textural and structural properties of mesoporous silica materials along with the template removal mechanism and their pores and coins.

Synthesis and Application of Mesoporous Materials: Process Status, Technical Problems, and Development Prospects: A Mini-Review

“…Because of their relatively homogeneous structure, materials synthesized using the hard templating method typically have a more uniform morphology. Many different forms of materials can be synthesized using the soft templating method without requiring complex equipment, and the template agent can be removed relatively easily Figure shows the preparation process of the ordered mesoporous materials using the templating methods.…”

“…Many different forms of materials can be synthesized using the soft templating method without requiring complex equipment, and the template agent can be removed relatively easily. 45 Figure 5 shows the preparation process of the ordered mesoporous materials using the templating methods. 48 explained how the unique synergy between mesoporous silica synthesized in two steps by CO 2 extraction and using a nonionic template can help overcome the poor tolerance of most mesoporous silica materials to hydrothermal environments.…”

A Facile Fabrication of Ordered Mesoporous Carbons Derived from Phenolic Resin and Mesophase Pitch via a Self-Assembly Method

“…The obtained polymeric monolith was collected by filtration, washed with deionized water, dehydrated in an oven at 60 °C, and further retained at 80 °C for 12 h, which led to a color change of the polymeric monolith into salmon pink. Subsequently, the products were carbonized in a tubular furnace under an inert atmosphere (N 2 flow) by heating the products at a heating rate of 1 °C/min up to 600 °C and then maintained further for 6 h. Here, it should be noted that soft template was easily removed by conventional calcination at 600 °C [ 18 , 19 ]. The final products were denoted as OMC-meso-x (here, x denotes the amount of mesophase pitch used.…”

A Comparative Loading and Release Study of Vancomycin from a Green Mesoporous Silica

“…Calcination is the gold standard for the removal of organic templates used in synthesis but has several drawbacks when it comes to large-scale production. The process wastes all of the expensive organic templates and takes a lot of time and energy [ 26 ]. Therefore, shorter calcination times or even complete elimination of this step are significant financial-related objectives that the pharmaceutical industry is seeking to achieve.…”