Haibin Yang, Yihang Ye, Jiayu Chen, Hongzhi Cui
The growing demand for climate-resilient and functionally reliable buildings requires envelope materials to integrate thermal regulation, mechanical integrity, fire safety, environmental stability, and electromagnetic protection within lightweight porous structures. Herein, we report a competitive crystallization-orchestrated assembly strategy to fabricate gypsum cryogels (GC), defined as freeze-dried, gel-derived porous gypsum–polymer composites, via ice-templated confinement within a reversibly breakable/reassemblable polyacrylamide/carbon nanotube hydrogel. The proposed hydrogel-mediated processing effectively suppresses gravitational sedimentation and phase separation, while enabling controlled competition between gypsum crystallization and ice-templating. The resulting hierarchical architectures, tunable from macro- to nanoscale porosity, allow precise composition-dependent regulation of density and multifunctionality. The low-gypsum GC@1 achieves a low density of 70 kg·m⁻³ and an EMI shielding effectiveness of 38 dB. Conversely, the high-gypsum GC@25 with a density of 532 kg·m − 3 delivers a structural–insulation profile, exhibiting a compressive strength of 4.52 MPa (a 7433% increase over the gypsum-free matrix), a limiting oxygen index exceeding 90%, and robust hydrophobicity (water contact angle: 151.3°). Crucially, EMI shielding is retained across the series, with absorption dominating the attenuation mechanism even at high gypsum loadings. These results demonstrate that the GC series provides a tunable, composition-dependent platform for balancing insulation, mechanical strength, fire resistance, hydrophobicity, and EMI shielding in lightweight gypsum-based porous composites for advanced building-envelope applications.