Synthesis and characterization of nickel immobilized on aminated Periodic Mesoporous Organosilica

Periodic Mesoporous Organosilica (PMO) is a superior mesoporous silica material which has a meso-size and ordered pore structure as well as a large surface area. These properties support PMO to be applied as a metal catalyst support. Nickel is a metal that is widely used as a catalyst in various reactions, since this metal has d orbitals that are not fully filled. Therefore, it could actively interacts with reactants and facilitate the formation of intermediates on the surface of the catalyst. In this study, biphenylene-bridged PMO (Bph-PMO) was synthesized using 4,4'-bis(triethoxysilyl) biphenyl precursor in basic conditions, continued with amine functionalization through nitration and amination to produce NH2− Bph-PMO. Immobilization of nickel was conducted using Ni(acac)2 as precursor in toluene as solvent to obtain Ni/NH2− Bph-PMO. Characterization with XRD shows that functionalization of amine groups as well as immobilization of Ni does not change the periodic structure in Bph-PMO, with diffraction peaks (2θ) observed at 7.43°, 14.93°, 22.54°, 30.22°, and 38.10°. TEM analysis shows mesoporous crystal-like structure of NH2−Bph-PMO. Morphological characterization with SEM reveals the slightly rough and spherical surface of NH2−Bph-PMO and Ni/NH2−Bph-PMO with average particle size of 345 nm and 420 nm, respectively. Nickel complex was successfully immobilized on NH2−Bph-PMO with 2.8 % metal loadings, as confirmed with EDX analysis. FTIR analysis shows that nitration and amination processes were successfully performed as confirmed by the presence of new peaks at 1563 cm-1 and 1352 cm-1 for NO2−Bph-PMO, and peak at 1616 cm-1 for NH2−Bph-PMO. Immobilization of nickel on NH2−Bph-PMO generates new peak at 1525 cm-1 which indicates that C=N bond formed due to Schiff base condensation.