SiO2-layered double hydroxide microspheres and methods of making them

Silica-layered double hydroxide microspheres having the formula I below

• (SiO2)p@{[Mz+(1-x)M′y+x(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent)}q (I)
• wherein,
• Mz+ and M′y+ are two different charged metal cations;
• z=1 or 2;
• y=3 or 4;
• 0<x<0.9;
• b is 0 to 10;
• c is 0 to 10;
• p>0,
• q>0;
• Xn− is an anion;
• with n>0;
• a=z(1−x)+xy−2;
• and
• AMO-solvent is an 100% aqueous miscible organic solvent,
• wherein the silica-layered double hydroxide microspheres each comprise a SiO2 microsphere having solid layered double hydroxide attached to its surface, and wherein:
• A. the silica-layered double hydroxide microspheres are core-shell materials wherein the SiO2 microsphere is a solid sphere, and wherein the specific surface area of the core-shell materials is at least 100 m2/g, or
• B. the silica-layered double hydroxide microspheres are yolk-shell materials wherein the SiO2 microsphere comprises an outer shell and a smaller SiO2 sphere contained within the outer shell, wherein there is a hollow portion between the smaller sphere and the inner surface of the outer shell, and wherein the specific surface area of the yolk-shell materials is at least 100 m2/g, or
• C. the silica-layered double hydroxide microspheres are hollow shell materials wherein the SiO2 microsphere has a hollow interior, and wherein the hollow shell materials have a specific surface area of at least 130 m2/g;
• and wherein the silica-layered double hydroxide microspheres have a thickness of layered double hydroxide layer larger than 110 nm.