Crystalline frameworks composed of hexacoordinate silicon species have thus far only been observed in a few high pressure silicate phases. By implementing reversible Si-O chemistry for the crystallization of covalent organic frameworks

we demonstrate the simple one-pot synthesis of silicate organic frameworks based on octahedral dianionic SiO 6 building units.Clear evidence of the hexacoordinate environment around the silicon atoms is given by

29

Si nuclear magnetic resonance analysis. Characterization by high-resolution powder X-ray diffraction

density functional theory calculation and analysis of the pair-distribution function showed that those anionic frameworks-M

2

[Si(C

16

H

10

O

4

)

1.5

]

where M=Li

Na

K and C

16

H

10

O

4

is 9

10-dimethylanthracene-2

3

6

7-tetraolate-crystallize as two-dimensional hexagonal layers stabilized in a fully eclipsed stacking arrangement with pronounced disorder in the stacking direction. Permanent microporosity with high surface area (up to 1276m

2

·g

-1

) was evidenced by gas-sorption measurements.