[EN] Micropores and their interplay with liquids are critical in many solid systems but challenging to investigate, often requiring complex and indirect techniques to even be detected. Here, we perform low-field H NMR transverse relaxometry on submicron Stöber silica spheres to directly detect micropore water. Colloidal crystals with a well-defined sphere configuration are used to facilitate unambiguous distinction of the interparticle void water and enable straightforward micropore volume quantification. We evidence significant microporosity (∼16% of the sphere volume) with high water accessibility and monitor the drying of the micropore water, which exhibits high resilience, evaporating only after complete void drainage. Progressive microporosity closure by thermal annealing above 600 °C is shown, until complete removal at 900 °C. Increasing hydrophobicity of the micropore walls is observed, although it barely affected the water access. Our results prove the capability of NMR relaxometry to quantitatively investigate complex microporosity and the behavior of water confined therein.

Spanish MINECO project MAT2014-58731-JIN and MCIU grant RTI2018-093921-BC41. I.A. acknowledges the partial support of the project 21 PFE in the frame of the program PDI-PFE-CDI 2018.