Hexagonal mesoporous silica layers were prepared by the sol–gel route using silicon alkoxides as silica precursors and alkyltrimethylammonium bromides to form the templating liquid crystal mesophase. The synthesis conditions required to obtain well-ordered crack-free layers were investigated. Thin layers exhibiting these properties were deposited from diluted sols. X-Ray diffraction enabled characterisation of the thermal evolution of their ordered structure and crystalline texture. Their porosity was experimentally measured from nitrogen adsorption–desorption analyses carried out directly on the thin layers. Two main synthesis parameters were identified. The first is the ageing time of the sol before deposition: ²⁹Si NMR showed that the disappearance of the ordered structure in the layers is related to the appearance of the Q₃ species in the sol. The second important synthesis parameter is the surfactant volume fraction in the medium after the removal of the volatile components. Using hexadecyltrimethylammonium bromide, well-ordered hexagonal layers were obtained for surfactant volume fractions ranging from 0.5 to 0.65, as expected from the corresponding water–surfactant binary diagram. For surfactants with shorter alkyl chains, the domain of existence of the hexagonal layers shifts to higher surfactant volume fractions in agreement with the evolution previously observed on the water–surfactant binary diagrams.

Lattice Boltzmann simulations show how fluid flow can perturb adsorption in complex porous media.

We study here the interplay between transport and adsorption in porous systems with complex geometries under fluid flow. Using a lattice Boltzmann scheme extended to take into account the adsorption at solid/fluid interfaces, we investigate the influence of pore geometry and internal surface roughness on the efficiency of fluid flow and the adsorption of molecular species inside the pore space. We show how the occurrence of roughness on pore walls acts effectively as a modification of the solid/fluid boundary conditions, introducing slippage at the interface. We then compare three common pore geometries, namely honeycomb pores, inverse opal, and materials produced by spinodal decomposition. Finally, we quantify the influence of those three geometries on fluid transport and tracer adsorption. This opens perspectives for the optimization of materials’ geometries for applications in dynamic adsorption under fluid flow.