Industrially compatible synthesis of MCM-41 with spatial organization at the macro- mesoscale

Nowadays industrial requirements point to high-performance processes but cost-effective materials to maximize their benefit/cost balance. This paper describes the properties of a macro- mesoporous MCM-41 silica with very high surface area obtained from inexpensive reagents —industrial sodium silicate as a source of silicon and industrial CTAC as template— with potential use in an environmental application such as CO2 capture. The MCM-41 silica exhibits an aperiodic 3D hierarchical spatial organization at the macro-mesoscale, formed by well-ordered MCM-41 particles with bowl-like mesopores. These particles are interconnected in three dimensions, creating a web-like structure that imparts macroporosity. This organization can be rationalized in terms of the nature and interaction of the reactants. Thus, the conjunction of poly (N-silicate) and features in CTAC, such as the weakly bonding counterion (Cl−), ethanol and unreacted amine, gave rise to different morphologies and variable channel lengths, porosity at different length scales producing meso/macro arrangements, and a spongy structure as a disordered minority phase. The hierarchical organization enhances the potential of the material for uniform APTS loading, thereby improving CO2 capture. Then the use of industrial reactants offers two important advantages: (i) The presence of macro- mesocavities, enabling applications requiring greater porosity than that intrinsic to MCM-41; (ii) A reduction in production costs by at least 80% compared to traditional synthesis methods using alkoxysilanes and CTAB, and negligible costs compared to synthesis with analytical grade CTAC. In summary, this study demonstrates the synthesis of a hierarchically structured MCM-41 silica using cost-effective industrial reagents, offering a promising and economical solution for different applications.