An all-in-one microgel-derived cellulosic triboelectric foam for robust and sensitive CO2 monitoring.

The reliance of conventional carbon dioxide (CO₂) sensors on external power limits their application scope. Self-powered triboelectric nanogenerators offer a promising alternative, yet the development of high-performance triboelectric sensing materials remains a key challenge. This study presents an ingenious design using microgels from polyethyleneimine (PEI)-crosslinked nanocellulose as dual-functional building blocks to fabricate a mechanically robust and CO2-sensitive triboelectric foam. The microgels (optimized with 25,000 Da PEI) formed an optimal pore-forming template, facilitating the efficient and uniform distribution of PEI. The resulting cellulose foam achieves an excellent combination of high porosity (85.6%), low density and compressive toughness (1.37 MJ m-3), while functioning dually as the triboelectric layer and the CO2 sensing material. The optimized TENG-based sensor enables sensitive CO₂ responsiveness, exhibiting a good linear relationship (R2 = 0.99) within 750-2500 ppm, and maintaining robust signal output. This study provides a novel strategy for developing CO2-sensitive materials and significantly advances the application of triboelectric CO₂ sensors in air quality monitoring.