3D imaging of dry and liquid-impregnated mesoporous materials

The performance of mesoporous materials in applications, such as drug delivery, batteries, and heterogeneous catalysis, strongly depends on their pore structure. Traditionally, this structure is assessed using bulk characterization techniques such as nitrogen physisorption. In contrast, direct nanoscale visualization through electron microscopy (EM) offers valuable qualitative and quantitative insights of pore morphologies. This short review discusses EM approaches for visualizing mesopores in 3D, details structural mesopore descriptors accessible through these methods, and highlights recent advances in cryogenic electron tomography (cryo-ET) for imaging beam-sensitive and liquid-impregnated mesopores. In addition to this discussion, (cryo)ET is compared to other nanoscale imaging approaches and challenges associated with (cryo-)ET sample preparation, acquisition, and segmentation of reconstructions are addressed. Ultimately, we argue that a broader adoption of (cryo-)ET will significantly advance the fundamental understanding of mesoporous materials, their preparation and functionality.