Tuning multi-scale pore structures in carbonaceous films via direct ink writing and sacrificial templates for efficient indoor formaldehyde removal

The primary challenges impeding the extensive application of adsorption for indoor air purification have been low efficiency and effective capacity. To fill the research gap, we developed carbonaceous net-like adsorption films featuring multi-scale porous structures for efficient indoor formaldehyde removal. By optimizing the interfacial mass transfer and internal diffusion, we designed macro- to mesoscale meshes on the film surface and micro- to nano-scale pores within the materials, which were achieved by direct-ink-writing (DIW) printing and sacrificial template methods, respectively. Compared to unmodified planar films, the developed films exhibited a significant increase in the initial single-pass efficiency of formaldehyde from 68.1 % to 89.0 %, with the 8-hour effective adsorption capacity (EAC_ad) spiking from 2.74 mg/g to 8.60 mg/g. Through thermal regeneration, the film demonstrated stable operation for 30 days through a long-term experiment over 250 hours, and EAC_ad significantly increased to 241.7 mg/g. The multi-scale adsorption films achieved nearly the highest purification rates and capacities among existing physisorption and chemisorption technologies, with the lowest energy cost of 0.37 kW·h per day. The innovative design and fabrication of multi-scale adsorption films evidence its substantial application for indoor formaldehyde purification and provide a viable solution for carbon capture and gas separation in environmental engineering.