Construction of Hierarchical Porous Composite Aerogel for High‐Efficient Removal of Low‐Level Gaseous Formaldehyde

Abstract Formaldehyde (HCHO), a pervasive indoor pollutant with chronic toxicity, poses severe health risks even at sub‐ppm levels, making its effective removal challenging. Herein, a dual‐functional aerogel integrating selective adsorption and catalytic oxidation is developed for ambient HCHO elimination. Specifically, Pt‐loaded hollow mesoporous MnO ₂ (Pt@hmMnO ₂ ) nanospheres are first synthesized, achieving 97.8% HCHO removal (1 mg m ⁻³ ) under light through synergistic adsorption‐photothermal catalysis. A hierarchical porous aerogel architecture is constructed via a two‐step freezing method, embedding the Pt@hmMnO₂/cellulose nanofibers (CNF) mixture within the unidirectionally frozen chitosan (CS) matrix. The obtained 3D framework (named as CS/Pt‐CNF) features abundant ─NH ₂ groups and through‐hole channels enabling selective HCHO capture and accumulation. The unique bilayer design achieves rapid HCHO reduction from 1 to 0.044 mg m ⁻³ within 60 min, which is below the international standard (0.08 mg m ⁻³ ). The pre‐concentration effect synergizes with the catalytic nanospheres to degrade adsorbed HCHO into CO₂ and H₂O, maintaining 97.4% efficiency after five cycles without adsorbent saturation. Mechanistic studies reveal that the macroporous CS layer facilitates gas diffusion while mesoporous Pt@hmMnO ₂ ensures molecular activation, collectively enabling faster reaction kinetics than conventional powder catalysts. Such an eco‐friendly CS/Pt‐CNF aerogel demonstrates the practical potential for enclosed environments through simultaneous pollutant confinement and destruction.