A random google link says that you would need hundreds of plants per person to get sufficient oxygen production [1].

And during night, the plants would just produce CO2, which would presumably get accumulated, making the whole situation worse.

[1] - https://io9.gizmodo.com/5955071/how-many-plants-would-you-ne...

Plants have have been shown to capture other contaminants in the air as well, I haven't seen any capture capacity over any time scale. I wonder if anyone has done the metrics.

Plants did not get approved ;)