*2.6. Differential Scanning Calorimetry (DSC)*

PXRD and DSC measurements were performed simultaneously using an XRD-DSC (Rigaku, Japan) equipped with a D/tex Ultra detector and Cu Kα source (40 kV, 40 mA). A powdery sample of DIC-Na 4.75H was heated at +1 ◦C min−<sup>1</sup> up to 120 ◦C in an unsealed Al pan with flowing N<sup>2</sup> gas (100 mL min−<sup>1</sup> ). The preliminary DSC measurement was performed up to 300 ◦C to confirm the absence of phase transformation over 150 ◦C (Figure S1, the Supplementary Materials).
