This review focuses on important aspects of applying physisorption for the pore structural characterization of hierarchical materials such as mesoporous zeolites. During the last decades major advances in understanding the adsorption and phase behavior of fluids confined in ordered nanoporous materials have been made, which led to major progress in the physisorption characterization methodology (summarized in the 2015 IUPAC report on physisorption characterization). Here we discuss progress and challenges for the physisorption characterization of nanoporous solids exhibiting various levels of porosity from micro- to macropores. While physisorption allows one to assess micro- and mesopores, a widely employed method for textural analysis of macroporous materials is mercury porosimetry and we also review important insights associated with the underlying mechanisms governing mercury intrusion/extrusion experiments. Hence, although the main focus of this review is on physical adsorption, we strongly emphasize the importance of combining advanced physical adsorption with other complementary experimental techniques for obtaining a reliable and comprehensive understanding of the texture of hierarchically structured materials.

In order to investigate the details of the process of pore condensation and hysteresis mechanisms in three-dimensional (3-D) pore networks, we performed a systematic study of the adsorption and pore condensation behavior of N2 (77.4 K) and Ar (77.4 and 87.3 K) in a 3-D ordered pore system, i.e., cubic Ia3̅d mesoporous KIT-6 silica materials with mode pore diameters ranging from ca. 5 nm up to 11 nm. KIT-6 silica is a porous material composed of two intertwined mesoporous subnetworks similar as in MCM-48, but this material can be prepared with much larger mean pore diameters. Accurate pore size analysis was performed by X-ray diffraction modeling and by state-of the art application of nonlocal density functional theory (NLDFT) on N2 (77.4 K) and Ar (87.3 K) sorption data. Furthermore, our data suggest that the width of the adsorption/desorption hysteresis loop observed for 3-D KIT-6 silica can be narrower as compared to that of pseudo-one-dimensional SBA-15 silica of the same pore size (i.e., in the pore diameter range from 6 to 8 nm). This specific behavior correlates well with the existence of the highly interconnected 3-D pore network of the KIT-6 material. Moreover, the results of our investigations are also consistent with previous observations that the SBA-15 pore system becomes more and more interconnected with increasing aging temperatures, i.e., SBA-15 changes from being a material with a pseudo-one-dimensional mesopore system to a material exhibiting a three-dimensional pore system resembling KIT-6 silica. These results provide new insights into the effects of pore interconnectivity on pore condensation and hysteresis behavior in both KIT-6 and SBA-15 silica materials and enable a more thorough understanding of the pore structure and textural properties of these materials.

We report here on an efficient one-step-impregnation method to synthesize crystalline mesoporous bimetal oxides (e.g. NiFe(2)O(4), CuFe(2)O(4), Cu/CeO(2)) using mesoporous silicas as hard templates under optimized mixing conditions. This new procedure enables a true replication of the mesostructure with high yield and phase purity, while retaining particle morphology of the template.

Metal-organic frameworks (MOFs) are commended as photocatalysts for H2 evolution and CO2 reduction as they combine light-harvesting and catalytic functions with excellent reactant adsorption capabilities. For dynamic processes in liquid phase, the accessibility of active sites becomes a critical parameter as reactant diffusion is limited by the inherently small micropores. Our strategy is to introduce additional mesopores by selectively removing one ligand in mixed-ligand MOFs via thermolysis. Here we report photoactive MOFs of the MIL-125-Ti family with two distinct mesopore architectures resembling either large cavities or branching fractures. The ligand removal is highly selective and follows a 2-step process tunable by temperature and time. The introduction of mesopores and the associated formation of new active sites have improved the HER rates of the MOFs by up to 500%. We envision that this strategy will allow the purposeful engineering of hierarchical MOFs and advance their applicability in environmental and energy technologies.