Recent advances in formaldehyde adsorption by metal–organic frameworks for indoor air filtration

Formaldehyde is a common indoor volatile organic compound emitted from building materials, furnishings, and household products. As a recognized human carcinogen, formaldehyde exposure leads to acute irritation of the eyes, skin, and respiratory tract, while long-term exposure elevates risks of leukemia and lung cancer. Metal-organic frameworks (MOFs) have recently emerged as potent, tunable adsorbents for formaldehyde removal in Heating, Ventilation, and Air Conditioning (HVAC) filtration systems. Their crystalline frameworks, composed of metal nodes and organic linkers, offer ultrahigh surface areas, well-defined pore structures, and flexible chemical functionality. Compared with traditional adsorbents such as activated carbon, MOFs can deliver faster adsorption kinetics, lower regeneration temperatures, and improved selectivity under low-concentration indoor conditions. This review comprehensively surveys recent advances in MOF-based formaldehyde adsorbents, focusing on how metal nodes, organic linkers, and key adsorption parameters influence performance. We examine design strategies including pore-size engineering, polarity/hydrophobicity tuning, functional group modification, and MOF-based composites. Practical aspects such as humidity stability, competitive CO₂ adsorption, kinetics, long-term stability, and reusability in indoor environments are also evaluated. Finally, we discuss fabrication and integration pathways for real-world air filtration systems, with the aim of guiding rational design and implementation of next-generation MOF-based purifiers.