SiO2-layered double hydroxide microspheres and methods of making them

A method of making silica-layered double hydroxide microspheres, each having a silica microsphere core and a layered double hydroxide coating on the surface of the silica microsphere core, the silica-layered double hydroxide microspheres having the formula I

• (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
• the AMO-solvent is an 100% aqueous miscible organic solvent;
• which method comprises the steps:
• (a) contacting:
• (i) silica microspheres,
• (ii) a metal ion containing solution containing metal ions Mz+ and M′y+, and
• (iii) an anion solution
• in the presence of a base to grow a layered double hydroxide coating on the surface of the silica microspheres;
• (b) collecting the product;
• and
• (c) optionally treating the product with AMO-solvent and recovering the solvent treated material to obtain the silica-layered double hydroxide microspheres;
• wherein the pH of the reaction solution formed in step (a) is controlled within a range from 8 to 12;
• and wherein the silica-layered double hydroxide microspheres have a thickness of layered double hydroxide of larger than 110 nm.