Metal-Induced Aminosilica Rigidity Improves Highly Permeable Microporous Membranes via Different Types of Pendant Precursors

In this study, nickel-doped aminosilica membranes containing pendant groups were prepared with 3-aminopropyltriethoxysilane (APTES), trimethoxy[3-(methylamino)propyl]-silane (MAPTS), 3 N,N-dimethyl aminopropyltrimethoxysilane (DAPTMS), N-[3-(trimethoxysilylpropyl]ethylene diamine (TMSPED), and 1-[3-(trimethoxysilyl)propyl] urea (TMSPU). Differences in the structures of terminal amine ligands significantly contributed to the formation of a coordinated structural assembly. Ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and N-2 adsorption isotherms revealed that short and rigid pendant amino groups successfully coordinated with nickel to produce subnanopores in the membranes, while an ion-exchange interaction was suggested for longer and sterically hindered aminosilica precursors. Moreover, the basicity of amine precursors affected the affinity of ligands for the development of a coordinated network. A pristine aminosilica membrane showed low levels of H-2 permeance that range from 0.1 to 0.5 x 10(-6) mol m(-2) s(-1) Pa(-1 )with a H-2/N-2 permeance ratio that ranges from 15 to 100. On the contrary, nickel coordination increased the H-2 permeance to 0.1-3.0 x 10(-6) mol m(-2 )s(-1) Pa-1 with H-2/N-2 permeance ratios that range from 10 to 68, which indicates the formation of a microporous structure and enlargement of pore sizes. The strong level of coordination affinity between nickel ions and amine groups induced rearrangement of the flexible pendant chain into a more rigid structure.

Automated summary

In this study, nickel-doped aminosilica membranes were prepared using different terminal amine ligands, and the differences in ligand structures significantly affected the formation of coordinated structures. The coordination of short and rigid pendant amino groups with nickel resulted in the formation of subnanopores, while longer and sterically hindered aminosilica precursors likely underwent an ion-exchange interaction. The basicity of amine precursors also influenced the development of a coordinated network.