[newsuser]

Carl Sagan proposed something along the lines in 1961 (but using bacteria to convert CO2 to graphite), however later it became clear that wouldn't work, in part, because the depth of the created sediment layer would be >100 meters.

https://en.wikipedia.org/wiki/Terraforming_of_Venus

[actionfromafar]

What's wrong with a 100 meter sediment layer?

Edit: apparently, as per Wikipedia, in the high pressures of Venus, the resulting pure oxygen atmosphere would combust the solid carbon sediment, going straight back to the same carbon dioxide atmosphere is has now.