Self-assembly structural transition of protic ionic liquids and P123 for inducing hierarchical porous materials

Abstract

Hierarchical micro–mesoporous silica–zirconium has been obtained by adjusting the interaction between protic ionic liquids (NTA) and Pluronic 123 surfactant through changing the content of NTA and the pH of the solutions. This has resulted in modification of the packing of NTA micelles and P123 micelles, leading to silica–zirconium with different textural and structure characteristics. The structure, crystalline state and textural properties of the materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) analyses and nitrogen adsorption/desorption techniques. The results revealed that NTA displayed notable synergic interaction with P123 by changing the pH of the solution. Two kinds of pore channels could be observed from the materials when the pH was 2. When increasing the pH, a mesocelluar foam, branch-like structure and sphere structure were synthesized, indicating NTA and P123 can exhibit different forms in water at different pH values, which strongly influences the interaction between the NTA and P123, and sequentially changes the self-assembly structure of the mixed micelles in water. Moreover, the formation mechanism of the hierarchical porous silica–zirconium which is based on the interaction between NTA and P123 is tentatively elucidated by studying the size of the NTA/P123 micelles at different compositions. The catalytic behaviors of the materials were investigated in the alkylation of o-xylene with styrene.