The ever increasing CO2 being the main driver of all the climate related changes and seemingly green plants seem to be the major solution to reduce the concentration, how much have we made a progress in knowing the most effective plants?
There are plants with exceptional ability to remove CO2 from the atmosphere such as Azolla which is speculated to have put an end to a very hot greenhouse gas dominated period back in Eocene. https://en.wikipedia.org/wiki/Azolla_event
All living plants absorb CO2 ,but trees significantly more than smaller plants due to their large size and extensive root structures.Also,some trees like Pine, Oake, Bald Cypress, London Plane, American Sweetgum are better than others at absorbing carbon dioxide. The faster a plant grows, the more carbon dioxide it will absorbs. Plants like Azolla, Ferns and Algae are considered nature's most efficient CO2 absorbers.