Developing inexpensive and highly efficient CO2 air capture technologies is an important solution for solving the greenhouse problem. In this work, we used the low-cost quaternized chitosan (QCS)/poly(vinyl alcohol) (PVA) hybrid aerogels with quaternary ammonium groups and hydroxide ions to reversibly capture CO2 from ambient air by humidity swing. The CO2 capture capacity and adsorption rate of the aerogels were investigated over the temperature range 10-30 degrees C. The CO2 capture capacity of the aerogels was measured to be about 0.18 mmol/g, which is 38% higher than the state-of-the-art commercial membrane. In addition, we proposed a modified pseudo-first-order kinetic model considering both the CO2 adsorption and the H2O desorption, which describes the experimental results very well. For the first time, the moisture-swing CO2 adsorbent is built by low-cost biomass material, which opens up a new approach for the design of the moisture-swing CO2 adsorbent.