Fig. 2: Structural characterizations.

a–f, Scanning electron microscopy images with different magnifications of the CCAP hydrogel: top view (a–c); side view (d–f). g, Elemental mappings of the hydrogel. h, Cryo-Raman spectra showing the fitting peaks of ice (red and green lines) and bound water (blue and bright blue lines) in precursor solution for the fabrication of CCAP hydrogel recorded at −18 °C. i, Temperature-modulated DSC scan (black line) of the precursor solution for the fabrication of CCAP hydrogel at a heating rate of 5 K min⁻¹. The red line shows the reversible part of the heat flow. The asterisks indicate the melting points of bound water (267.8 K) and ice (274.5 K).