A Sustainable Route toward Gradient‐Structured Sponge with Topological Cellular Cavity from Bamboo for All‐Season Comfort

ABSTRACT Thermoacoustic regulation in buildings is essential for enhancing occupant comfort, yet integrating this dual functionality into a single material remains challenging. Here, we present an eco‐friendly, closed‐loop strategy for fabricating a high‐performance thermoacoustic regulator from fast‐growing young bamboo (SiBG). This material leverages a novel gradient architecture coupled with topological honeycomb cavities to transcend conventional performance limits. The distinctive structure results from a minimal‐processing strategy: ice‐templating re‐engineers the natural gradient, and concurrent ethanol treatment removes soluble components. By integrating solvent recycling, this process achieves a closed‐loop recycling with zero waste discharge. SiBG exhibits superior specific strength (16.04 MPa cm 3 g −1 ), ultralow radial thermal conductivity (0.025 W m −1 K −1 ), a high noise reduction coefficient of 0.38 (9 mm thickness), and water resistance. Mechanistically, the integration of gradient pores and honeycomb cavities achieves spatial decoupling of thermoacoustic transport. The gradient porosity minimizes acoustic reflection via impedance matching, while the internal honeycomb framework effectively constrains thermal dissipation. A simplified thermal model confirms that SiBG provides all‐season comfort as building insulation, and energy modeling predicts 32%–46% savings in cold climates. This work underscores the sustainable value and structural uniqueness of SiBG, positioning young bamboo as a competitive alternative to conventional thermoacoustic regulation materials.