In-situ synthesis of KAUST-7 membranes from fluorinated molecular building block for H2/CO2 separation

• Main Authors: Dong, Y. (Author), He, G. (Author), Lu, J. (Author), Lv, J. (Author), Wang, L. (Author), Yang, J. (Author), Zhou, X. (Author)
• Format: Article
• Language: English
• Published: Elsevier B.V. 2022
• Subjects: Alumina; Aluminum oxide; Aluminum Oxide; Anatomy; Binary mixtures; Corrosion; Defect-free; Fluorinated molecular building block; Greener solvents; H2/CO2 separation; Hydrofluoric acid; Hydrofluoric Acid; In-situ synthesis; KAUST-7 membrane; Membranes; Molecular building blocks; Morphology; Nickel compounds; Nickel Compounds; Nucleation; pH manipulation; Ph manipulation; Separation; Synthesised; Tubulars
• Online Access: View Fulltext in Publisher

 A well-intergrown and defect-free tubular KAUST-7 membrane was fabricated via in-situ synthesis assisted by fluorinated molecular building block using green solvent of water on coarse asymmetric α-Al2O3 tubes. The strategy averted the serious corrosion of high-concentration hydrofluoric acid (HF) to α-Al2O3 supports due to the substitution of HF with the pre-synthesized NiNbOF5, overcoming the difficulty of serious corrosion to supports compared to traditional one-pot synthesis. The pH manipulation of synthesis solution is proved crucial to the fabrication of defect-free KAUST-7 membranes. In addition, effects of reactant concentration, crystallization temperature and reaction solvents on the morphology and separation performance of KAUST-7 membrane were investigated. The optimized KAUST-7 membrane M4 exhibited a H2 perm-selectivity of 17.7 over CO2 for H2/CO2 binary mixture with a H2 permeance of 2.2 × 10−7 mol m−2 s−1 Pa−1 at 25 °C and 1 bar, while the H2/CO2 separation factor just had a slight decrease when test temperature increased to 120 °C. The formation mechanism of KAUST-7 membranes via in-situ method in this work was investigated by exposing a bare α-Al2O3 tube into NiNbOF5 aqueous solution at the pH of 4.0 at 130 °C for 12 h. XPS and FT-IR observations revealed the formation of AlFxOy or AlFx species, which were deduced to be acted as linkers to connect with 2D Ni (II)-pyrazine layers, promoting the heterogeneous nucleation of KAUST-7 crystals on the surface of Al2O3 support. © 2022 Elsevier B.V.