Layered double hydroxide/sepiolite heterostructured materials

• Layered double hydroxide–sepiolite nanoarchitectures
• Heterostructured materials with simultaneous anionic and cationic exchange properties
• Clay-based nanostructured systems for application in adsorption processes and heterogeneous catalysis

This paper reports a new type of heterostructured materials based on the assembly of layered double hydroxides (LDH) to sepiolite fibrous clay. The assembly of Mg-Al and Zn-Al LDH has been explored following two procedures of synthesis: i) co-precipitation of the LDH in the presence of the clay; and ii) LDH reconstruction from the corresponding so-called “layered double oxide (LDO) phase” also in the presence of an aqueous dispersion of the clay. The resulting LDH/sepiolite nanoarchitectures were characterized by diverse physicochemical techniques (XRD, TG-DTA, FTIR, 29Si NMR, SEM and TEM), revealing the interaction of the generated LDH with sepiolite through the silanol groups at the external surface of the silicate. N2 adsorption–desorption isotherms evidence the effect of the sepiolite in providing a stable support for dispersing the LDH particles. The resulting materials show a relatively high external surface area and microporosity, with values depending on the sepiolite:LDH ratio in the final heterostructure. An interesting feature of these nanoarchitectures is related to the dual adsorption properties showing the possibility to simultaneously adsorb both cationic and anionic species. Moreover, the LDH can be transformed in the corresponding double metal-oxide by thermal treatment giving rise to nanoparticles that remain bonded onto the sepiolite fibers, which could be of interest in the preparation of highly disperse metal-oxide catalysts.