Mapping the Birth and Evolution of Pores upon Thermal Activation of Layered Hydroxides

The porosity of layered hydroxides can be greatly enhanced by thermal activation. Despite intense interest in the associated structural transformations, porosity changes have been almost exclusively described in terms of primitive bulk descriptors (surface area, pore volume, and average pore size), providing limited insight into the pore architecture (i.e., the geometry, location, and connectivity of the pores). This article maps porosity upon thermal activation of well-crystallized Mg(OH)2 (brucite) and isostructural layered double hydroxide {LDH, [M2+1–xM3+x(OH)2]x+(An–x/n)·mH2O} materials through novel characterization approaches such as transmission electron microscopy (TEM) coupled with in situ heating, differential hysteresis scanning (DHS) by high-resolution argon sorption, and positron annihilation lifetime spectroscopy (PALS). Despite exhibiting comparable surface area enhancements, arising from the formation of micro- and mesoporosity upon activation up to 873 K, the findings highlight striking ...