I'd participated on many a greenwash "CO2 sequester" tech call, and absolutely nobody was prepared to acknowledge that CO2 is 2/3 atomic oxygen (and almost 3/4 mass-proportion oxygen).
It's energy-intensive to isolate CO2 and then pump purified gas underground in huge quantities and "stay put!", doesn't want to obey.
To fix the artificial imbalance we gotta un-burn CO2 back into constituents, and isolate and sequester atmospheric carbon to reduce atmospheric CO2.
The plant kingdom draws in enormous quantities of CO2 but the moment any plant dies, all the CO2 returns to the air. It's a carbon cycle!
There was a brief period in Carboniferous era in which trees and plants were immune to decay, and whole forests became buried by geologic forces as coal.
Of course decay microbes have evolved and the world doesn't work that way any more.
Oh wait, there is one form of carbon that seems immune to decay, they call it plastic. Or graphite/graphene, coke, or diamonds, etc.
Just need a way to capture plant biomass prior to decay, transmute some proportion of the carbon into a durable form, and sequester that form.
(If we transmuted into 100s of billions of tons of diamond bricks, sure I'll use up some for a diamond brick veneer on the house. No probs!)