It has been confirmed that sustainable investments contributing to environmental protection can benefit from the deterioration of air pollution, but this influence mechanism has not been fully discussed. This paper proposes a mediation model to study air pollution's influence on green bonds. Theoretically, air pollution raises public environmental awareness and perceptions of physical health risks, leading to increased public concern. Enhanced public concern drives investors' green preference and environmental responsibility, thus expanding green bond demand. Our studies show air pollution is significantly positive related to public concern. Public concern positively links with green bond investment willingness, resulting in increased volatility. The total positive effect of air pollution on green bond is partly absorbed by the effect of public concern. These findings confirm the mediation role of public concern. In addition, major crisis events (e.g., COVID-19) may hinder the mediation process by generating a negative trend and distracting the public.