A simple ternary non-ionic templating system for preparation of complex hierarchically meso–mesoporous silicas with 3D-interconnected large mesopores

Abstract

This work for the first time demonstrated that hierarchically meso–mesoporous silicas can be facilely prepared in a simple ternary non-ionic surfactant templating system (TEOS/HCl(aq.)/P123) based on a previously reported partitioned cooperative self-assembly (PCSA) principle. As a result, unique clew-like hierarchically meso–mesoporous (HMM) silica particles with the first mode of worm-like mesostructures (3D-interconnected wormholes with pore size of 7–10 nm) and the second mode of 3D-interconnected intra-particulate mesochannels (16–32 nm in sizes) can be obtained in a controllable way without resorting to complicated synthesis procedures or special additives or multi-templates. Associated with the large mesopore sizes in both modes, very large mesoporosity (up to 2.37 cm³ g⁻¹) can be achieved. Based on systematic investigations on the synthesis conditions, synthesis domains for preparation of such HMM silicas were also presented. It is proposed that the formation of two mode mesoporosities follows different mechanisms: the first mode mesoporosity results from the self-assembly between P123 and silicate, though it is shown to be disordered due to the partitioning effect, while the formation of the second mode mesoporosity starts from loosely packed silicate/P123 hybrid aggregates/flocs formed upon the 1^st addition of TEOS, and then is initiated and finished by the 2^nd TEOS addition. This synthesis protocol therefore constitutes a new, simple and reliable pathway to prepare HMM silicas.