Cellulose microtubes/phenolic resin foam for stabilizing phase change materials and enhancing phase change performances.

Phase change materials (PCMs), typically represented by polyethylene glycol (PEG), inherently suffer from low thermal conductivity and inevitable liquid leakage during melting, which severely restrict their practical use in thermal management. In this study, cellulose microtubes (CMTs), which function as major structural elements in native wood tissues, were used as biomass-derived building blocks. With phenolic resin as a structural regulator, the CMTs were reassembled into three-dimensional foams and subsequently carbonized to form continuous and mechanically stable cellulose-phenolic resin carbon foams (CCFs). The resulting carbon framework not only enabled the effective encapsulation of PEG but also provided continuous heat-transfer pathways. The composite PCMs exhibited markedly enhanced thermal conductivity, reaching 0.49 ± 0.020 W·m-1·K-1, while maintaining relatively high phase-change enthalpy. Based on repeated DSC measurements, the DSC-estimated effective PEG contents of the composites ranged from 55.2% to 91.0%. Among them, CCF/PEG-15 showed the best overall balance between effective PEG accommodation, structural continuity, and leakage resistance, with a latent heat of 146.69 ± 13.17 J·g-1 and a leakage rate of only 1.90 ± 0.51% after 24 h at 80 °C. In addition, 50-cycle DSC testing confirmed good thermal reliability within the experimental scope of this study. This work highlights the structural potential of cellulose-based building blocks for constructing multifunctional porous carbon frameworks and provides a versatile strategy for shape-stabilized composite PCMs with improved thermal response behavior.