Water-deficient templating system: a general, versatile and efficient synthetic approach for mesoporous silicas

Abstract

Controlled synthesis of mesoporous silicas with tailorable mesostructures and particle morphologies has always been the research target of many materials scientists since the breakthrough in ordered mesoporous silicates in 1992, while the synthesis methodology is the key. Though standing out as a versatile and convenient approach, current non-ionic block copolymer (NBC) surfactant templating systems themselves in a broad sense polarize the two ‘extremes’: either being performed in far too diluted surfactant solution (DSS approach) or in much concentrated ones, i.e., liquid crystal phases (LCP approach). As a result, some limitations associated with each ‘extreme’ are also apparent: low silica content in synthesis mixture and therefore low synthesis efficiency and environmental unfriendliness mainly due to the high acid consumption for the DSS approach, while added synthesis complexity plus restricted functions for the LCP approach. Herein, we report a general, versatile and efficient synthetic approach, called water-deficient templating (WDT) system, bridging the above two ‘divided’ templating approaches based on the commonly used and commercially available NBCs, yet bearing some unusual characteristics in the templating manner that is different from those currently known. This approach to greater extent combines the advantages of both DSS and LCP approaches, enabling the facile engineering on the mesopore arrangements (wormhole-like, 2D-hexagonal or cubic), and effective adjustment in the mesopore sizes and facile tailoring in particle morphologies and even hierarchically macro–mesoporous monoliths. Moreover, significantly reduced synthesis volume and acid consumption in the WDT system re-assure that the NBC templated self-assembly process can be performed in this efficient and green way.