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Tailoring the Subnano Silica Structure via Fluorine Doping for Development of Highly Permeable CO 2 Separation Membranes
Author(s) -
Kanezashi Masakoto,
Matsutani Takuya,
Wakihara Toru,
Tawarayama Hiromasa,
Nagasawa Hiroki,
Yoshioka Tomohisa,
Okubo Tatsuya,
Tsuru Toshinori
Publication year - 2016
Publication title -
chemnanomat
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.947
H-Index - 32
ISSN - 2199-692X
DOI - 10.1002/cnma.201600045
Subject(s) - permeance , fluorine , doping , membrane , materials science , selectivity , chemical engineering , molecule , analytical chemistry (journal) , crystallography , nanotechnology , chemistry , chromatography , organic chemistry , optoelectronics , metallurgy , catalysis , biochemistry , engineering
The fluorine doping of a silica matrix was proposed in the design of enlarged and uniform networks for highly permeable CO 2 /CH 4 separation membranes. Fluorine doping effectively created a tunable network size, and the order of pore sizes increased with increases in the F concentration: F−SiO 2 (F/Si=2/8)>F−SiO 2 (F/Si=1/9)>SiO 2 . F−SiO 2 (F/Si=1/9) membranes showed high CO 2 permeance (4.1×10 −7 mol m −2 s −1 Pa −1 ) with high CO 2 /CH 4 selectivity (≈300) at 35 °C, due to the enlarged and uniform networks compared with those of SiO 2 . Fluorine doping was effective in preventing the formation of a 2nd Si−O in the 4‐membered ring (MR) of the SiO 4 tetrahedra. F−SiO 2 samples with smaller fractions of 4 MR and a smaller ring in silica, contain large fractions of larger rings (>5 MR), resulting in enlarged network structure and an increase in the average pore size, which translates to a higher permeance for larger molecules.