32.Sulfonic acid functionalization of 2-aminoterephthalate metal−organic framework and silica nanoparticles by surface initiated radical polymerization: as proton-conducting solid electrolytes

A post-polymerization method for metal–organic frameworks (MOFs) and silica nanoparticles have been developed to produce super-acidic solid nanoparticle. Thus, silica and amino-functionalized metal−organic framework [NH₂-MIL-101(Al)] were functionalized with 4.4′-Azobis(4-cyanovaleric acid) (ACVA) from hydroxyl and amine groups to yield initiator anchored silica and MOF nanoparticles. Then, sulfonated polymer/MOF and sulfonated polymer/silica hybrid nanoparticles were prepared by free radical polymerization of 2-acrylamido-2-methyl-1-propane sulfonic acid [(MOF-g-PAMPS) and (Si-g-PAMPS)], initiated onto the surfaces of initiator functionalized nanoparticles. Synthesis and modification of nanoparticles were characterized by fourier transform infrared (FTIR), thermogravimetric analysis (TGA). Also, the attachment of ACVA modifier agent on the surface of silica nanoparticles was studied using X-ray photoelectron spectroscopy (XPS). FTIR and TGA results indicated that AMPS monomer was successfully grafted onto the MOF and silica nanoparticles. The grafting efficiency of PAMPS polymer onto the silica and MOF nanoparticles were estimated from TGA thermograms to be 17 and 35 % for silica and MOF nanoparticles, respectively. Morphology of MOF and silica nanoparticles before and after modification processes were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively.