Theorical review of the interconnectivity of hierarchical porous materials – characterization by physical adsorption

Abstract

Hierarchically structured materials, with various levels of porosity, have been researched due to their properties, such as high surface area, accessibility to active sites and controlled mass diffusion. Characterization of these materials to determine pore size, surface area and pore size distribution is necessary for selection and performance optimization in many industrial applications (catalysis, adsorption, separation, energy and biochemistry). This review presents important aspects for the structural characterization of porous materials by gas adsorption, focusing on the interconnectivity of micro-mesopores. The general fundamentals of adsorption for the characterization of materials using independent pore model and development of theoretical and experimental studies for the characterization of materials with interconnected pores, illustrated with the characterization by advanced adsorption, were presented. In recent years, the progress in the synthesis of mesoporous materials, advances in experimental techniques and commercial instrumentation, microscopic approaches and computational methods have shown a great development in research to understand the structure-property relationship of these hierarchical materials. Gas adsorption is the most used method to characterize porous solids and is well established for independent pore modeling. However, the challenge for the development of models for interconnected pores persists. In materials with disordered pores, more research effort in the development of experimental techniques and molecular simulation is needed to understand the behavior of these heterogeneous materials.