Marine-derived photocatalysts for building envelopes: A review of materials, passive strategies, and physical implementation challenges

This review explores the innovative potential of integrating marine-based photocatalysts in the built environment, aiming to bridge the gap between sustainable material synthesis and performance-based envelope design. By analyzing 108 studies, the research addresses 10 primary questions concerning synthesis pathways, characterization techniques, and the transition from laboratory chemistry to building-relevant implementation. The analysis reveals that algae (41.7%) and seashells (38%), often combined with TiO 2 , ZnO, and Ag, serve as effective carriers (53.7%), reducing agents (36.1%), or photocatalysts themselves (10.2%). While these bio-composites demonstrate significant chemical potential, a critical disparity is identified: over 77% of current research targets wastewater treatment. This review critically evaluates the transferability of these liquid-phase findings to building physics applications, highlighting challenges in gas-phase pollutant diffusion and surface boundary layer interactions. Despite this gap, key positive findings demonstrate that marine-derived composites can achieve complete degradation of indoor pollutants, such as formaldehyde and toluene. Furthermore, bio-doping was shown to effectively reduce bandgap energies, enabling passive air purification under indoor light sources. The review concludes that future research must prioritize standardized gas-phase testing and long-term hygrothermal durability assessments to validate these materials for high-performance building envelopes.