Incorporation of single-walled aluminosilicate nanotubes for the control of crystal size and porosity of zeolitic imidazolate framework-L

Abstract

Zeolitic imidazolate framework-L (ZIF-L) is an emerging ZIF material possessing a unique two-dimensional layered crystal structure and a leaf-like crystal morphology. This paper reports a novel approach towards the incorporation of single-walled aluminosilicate nanotubes (AlSiNTs) into the interlayer of ZIF-L for the synthesis of AlSiNT@ZIF-L nanocomposites. The interlayer in ZIF-L is formed by hydrogen bonding between adjacent imidazoles. The resulting nanocomposites were subjected to a number of solid-state characterization techniques (SEM, TEM, powder XRD, EDS, TGA, nitrogen physisorption, and FT-IR) to elucidate the conformation of their microstructure. It was found that the AlSiNT@ZIF-L composite possesses an average crystal size considerably smaller than that of pure ZIF-L (1.1 μm for AlSiNT@ZIF-L and 7.8 μm for pure ZIF-L). Interestingly, ZIF-L and AlSiNTs are both microporous; however, the mesoporosity was achieved through the incorporation of AlSiNTs into ZIF-L crystals. A control experiment related to the synthesis of AlSiNT@ZIF-8 composites was performed to gain insight into the assembly pathway towards the formation of AlSiNT@ZIF-L crystals. Failure in the formation of AlSiNT@ZIF-8 supports the supposition that the assembly pathway involves the incorporation of AlSiNTs into the interlayer of ZIF-L, thereby facilitating the nucleation of ZIF-L crystals.