A novel malonamide bridged silsesquioxane precursor for enhanced dispersion of transition metal ions in hybrid silica membranes

Microporous hybrid silica membranes are known to have superior (hydro)thermal and chemical stability. By incorporating metal ions, such as Ce4+ and Ni2+ into these membranes, their affinity and selectivity towards particular gases may be altered. To promote the dispersion of metal ions within the hybrid silica matrix, the sol–gel precursor N,N,N′,N′-tetrakis-(3-(triethoxysilyl)-propyl)-malonamide (TTPMA) was synthesized. The malonamide ligands clearly coordinated the Ce4+ and Ni2+ metal centers and enhanced their dispersion. During annealing these metal centers redistributed into small nanosized grains of CeO2 (<5 nm) and Ni2O3 (<15 nm). These Ce-TTPMA and Ni-TTPMA membranes showed higher H2/N2 permselectivities as compared to previously reported hybrid silica membranes based on the 1,2-bis-(triethoxysilyl)ethane precursor. The TTPMA-precursor was found suitable for membrane separation and can be a promising and versatile precursor for the incorporation of metal ions within hybrid silica matrices.