After CO2-mediated desalination, the PEI-C16-Cl residue (containing both chloride and bicarbonate counter anions) was collected and subjected to TGA analysis (Figure ). A twostage mass loss was observed; the initial mass loss followed decomposition similar to that of protonated PEI (PEI-C16-H + ), whereas the subsequent phase (after 350 °C) aligned with the thermal decomposition profile of PEI-C16 and PEI-C16* (Figure ). This TGA result confirms that CO2-mediated desalination conditions led to partial protonation of PEI-C16, possibly forming ammonium salts (ammonium chloride and bicarbonate). Thus, investigating the exact distribution (homogeneity of anions) would be a critical future study.