Superior Antifouling Efficacy of Biomass-Based Furan-Heterocyclic Esters in Marine Antifouling Coatings

In the pursuit of alternative solutions to copper-based antifoulants, a total of 12 biomass-derived furan-heterocyclic esters were synthesized by employing a molecular hybridization strategy that utilized biomass-derived furfuryl alcohol along with heterocyclic acid. The structures of the synthesized compounds were confirmed by ¹H NMR and FTIR spectroscopy. These compounds were then formulated into antifouling coatings for further evaluation. Performance evaluation revealed coating hardness levels in the range of 3H-4H, and the adhesion strength varied from 2.54 to 3.04 MPa. After 14 days of hydrolysis, the water contact angle change and antifoulant release rate tended to stabilize, exhibiting good stability and controlled release characteristics. The biological activity experiment of the synthesized compounds showed significant inhibitory activity against marine bacteria and marine algae. Among these, furan-2-ylmethyl 2-(3-oxobenzo[<i>d</i>]isothiazol-2(3<i>H</i>)-yl)acetate (<b>1j</b>), furan-2-ylmethyl 1H-indole-2-carboxylate (<b>1k</b>), and furan-2-ylmethyl 2-oxochromane-3-carboxylate (<b>1l</b>) were particularly effective, exhibiting minimum inhibitory concentrations that could reach 16 mg/L, and at a mass concentration of 2 mg/mL, both the antibacterial and algal inhibitory rates exceeded 97%. Furthermore, these compounds also displayed significant inhibition and low ecotoxicity regarding the number of mussel byssal secretions, highlighting their environmental compatibility. During a 180 day marine field test, the coatings that incorporated these compounds successfully prevented the adhesion of fouling organisms such as barnacles. This research not only successfully developed a class of efficient, low-toxicity, sustained-release antifoulants using biomass materials but also verified their excellent antifouling performance in real sea conditions, paving the way for the advancement of environmentally friendly antifouling technologies.