Order–disorder–order mesophase transitions in self-assembled mesoporous alumina for enhanced CO2 adsorption

• Published in: Materials today chemistry Vol. 38; p. 102062
• Main Authors: Seah, Geok Leng, Corcoran, Edward W., Usadi, Adam K., McConnachie, Jonathan M., Tan, Kwan W.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2024
• Subjects: CO2 capture; DLVO; Mesophase transitions; Mesoporous alumina; Pore expander; Self-assembly; Solvation; DLVO; Self-assembly; Mesophase transitions; Solvation; Pore expander; Mesoporous alumina; CO2 capture
• ISSN: 2468-5194; 2468-5194
• DOI: 10.1016/j.mtchem.2024.102062

The addition of a hydrophobic micelle pore expander to self-assembling mesostructured hybrid materials enables access to new combinations with differently ordered mesophases and enhanced structural properties. Here we detail our investigations into the influence of 1,3,5-trimethylbenzene (TMB) on the self-assembly behaviors of an F127 Pluronic triblock copolymer with an aluminum oxide sol additive. By varying the chemical mixing sequence, the TMB-to-F127 mass ratio and the acid-to-metal molar ratio, we observe that TMB exhibits dual roles, functioning both as a hydrophobic swelling agent and as a low dielectric co-solvent. This induces a mesophase transition from an ordered p6mm lattice to a disordered state and subsequently back to the ordered p6mm phase. We propose a structure formation mechanism based on the DLVO theory to describe the thermodynamics and kinetic mobility of the hybrid micelles during the order-disorder and ensuing disorder-order mesophase transitions. The resulting ordered mesoporous alumina structures, with considerable pore sizes (up to 12 nm), high surface areas (up to 314 m2/g) and pore volumes (up to 0.74 cm3/g), organized pore geometry and variable inorganic wall thicknesses, have shown excellent CO2 adsorption capacities and are appealing for various applications, including stable high temperature catalyst supports, separation and sensing. •A facile method toward ordered mesoporous alumina with large pores, organized geometry, and variable wall thicknesses.•1,3,5-trimethylbenzene (TMB) acts as a pore expander and a low-dielectric co-solvent in F127-Al2O3 blends.•Increasing TMB concentration induces transitions from p6mm to a disordered structure and back to p6mm, consistent with DLVO theory.•Enhanced CO2 physisorption due to ordered structure and increases in pore size, surface area, microporosity, and isosteric heat.