Effect of counteranion of ammonium salts on the synthesis of porous nanoparticles (NH4)3[PMo12O40]

Porous ammonium phosphomolybdate ((NH 4 ) 3 [PMo 12 O 40 ]) nanoparticles have been synthesized by the titration method using several ammonium salts. The purpose of this work is to analyze the role of the counteranion in the development of the pore texture. The crystalline structure was quite similar in all the synthesized (NH 4 ) 3 [PMo 12 O 40 ] nanoparticles, as revealed by the similarity of the obtained powder X-ray diffraction patterns and the electron microscopy images. However, adsorption studies have shown pronounced differences in the pore texture of the different (NH 4 ) 3 [PMo 12 O 40 ] nanoparticles prepared. From these studies, it can be deduced that the counteranion of the ammonium salt plays an important role in the development of porosity during the synthesis of (NH 4 ) 3 [PMo 12 O 40 ]. It has been found an effect on both, the specific micropore area and the pore size distribution. The basic character of the counteranion has shown to be the main property affecting the development of mesoporosity in (NH 4 ) 3 [PMo 12 O 40 ] samples. On the other hand, the local concentration of [NH 4 ] + during the precipitation of (NH 4 ) 3 [PMo 12 O 40 ] seems to promote a higher porosity.