A human exhales about 1 kg of CO2 in a day (24 hours). That is about 270 grams of C. You'd need enough plants to sequester 270 grams of carbon, or about 0.5 kg of biomass (dry weight) per day, to "keep up" with your exhaling. This is much more than one houseplant.
rosemary is about 50% water [citation needed] and most of the dry part is carbohydrate, (ch₂o)ₙ, which should weigh [edited] 68% as much than the co₂, so roughly each kg of co₂ becomes 1.4 kg of rosemary
a doubling time of 66 days is about 1.05% growth per day, so you need about 130 kg of rosemary bush in your office to grow 1.4 kg per day and thus keep up with your exhaling
except actually it only needs to grow 1.4 kg per day during the daytime, not at night when it isn't photosynthesizing, so maybe you could get by with 90 kg of rosemary bush or so
and probably about half a tonne of soil, say about 2 m²
could be a single plant but it's kind of a tree-sized plant
if you need it to suck up your co₂ at night you need a crassulacean acid metabolism (cam) plant like aloe, but i think you need a larger amount of it because cam plants tend to grow slower. maybe moringa but i don't know if it's obligate cam or facultative cam
[edited to correct calculation erorr]
Which would be massive, and look absurd indoors.
Though maybe that's not a problem, since you shouldn't have anyone over who might laugh at and embarrass you over it - it'd then be only half as big as it needs to be!
might harbor moths tho
But offices! 90kg+ of living rosemary per person! When I worked in an office we didn't have anything like the space for that, even if you got rid of the desks and chairs and people. That would be quite something.
things like aloe and spekboom even less rainfall
then you could work nights
but this is starting to sound less like an office and more like the stuff i was writing about 9 years ago in https://dercuano.github.io/notes/underground-arcology.html
edible tho, like moringa
concrete carbonatation was eating the oxygen in biosphere 2