Direct cross-linking of silyl-functionalized cage siloxanes nonhydrolytic siloxane bond formation for preparing nanoporous materials

Bottom-up synthesis of siloxane-based nanoporous materials from siloxane oligomers is promising for constructing well-defined structures at a molecular level. Herein, we report the synthesis of nanoporous materials consisting of cage-type siloxanes through the nonhydrolytic siloxane bond formation reaction. Cage siloxanes with double- n -ring geometries ( n = 4 or 6) modified with dimethylsilyl and dimethylethoxysilyl groups are synthesized and directly cross-linked using a B(C 6 F 5 ) 3 catalyst, resulting in the formation of porous networks composed of alternating cage siloxane nodes and tetramethyldisiloxane (-SiMe 2 OSiMe 2 -) linkers. Compared with conventional hydrolysis and polycondensation reactions of alkoxysilyl-modified cage siloxanes under acid conditions, the non-hydrolytic condensation reaction was found favorable for the formation of porous siloxane networks without unwanted cleavage of the siloxane bonds. Nonhydrolytic siloxane bond formation reactions between cage siloxanes modified with dimethylsilyl and dimethylethoxysilyl groups in the presence of B(C 6 F 5 ) 3 catalyst are conducted to produce nanoporous materials with well-defined 3D networks.