oxygen plants
Heres plants list for increasing oxygen indoors and these plants not only release oxygen day and night, but also absorb Toxic gases like formaldehyde, benzene and others.
Scientifically, this happens through Crassulasian Acid Metabolism (CAM) type of photosynthesis can produces oxygen in night. Normally for Oxygen to be release there has to be photosynthesis which occurs only in the presense of light whether natural light or your indoor lights