CO2 is mainly transpoed in blood by

Reaction of Carbon Dioxide with Water in the Red Blood Cells--Effect of Carbonic Anhydrase. The dissolved CO2 in the blood reacts with water to form carbonic acid. In another fraction of a second, the carbonic acid formed in the red cells (H2CO3) dissociates into hydrogen and bicarbonate ions (H+ and HCO3-). Most of the H+ then combine with the hemoglobin in the red blood cells because the hemoglobin protein is a powerful acid-base buffer. In turn, many of the HCO3- diffuse from the red blood cells into the plasma, while chloride ions diffuse into the red blood cells to take their place.Ref: Guyton and Hall textbook of medical physiology 13th edition. Page: 535