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Terephthalic acid (H₂TPA) solubility in several ionic liquids (ILs) at multiple concentrations is higher than for any other known solvents at lower temperatures and pressures which suggests low energy purification of H₂TPA from its major impurity, 4-carboxybenzaldehyde (4-CBA) might be possible. To understand the mechanism several strategies were explored to purify H₂TPA by taking advantage of this high solubilizing power of ILs for H₂TPA in the crystallization of unique salts and cocrystals. Using either zwitterionic carboxylate IL-precursors or direct salt formation with carboxylate ILs or amines, a series of salts of mono, dibasic and two ionic cocrystals were obtained including monobasic, [C₁C₁im][HTPA], [N₄₄₄₁][HTPA], [C₄C₁im][HTPA]•0.5H₂TPA (a cocrystal), and [C₁Him][HTPA] ([C₁C₁im]⁺ = 1,3-dimethylimidazolium, [N₄₄₄₁]⁺ = tribuytlmethylammonium, [C₁Him]⁺ = 1-methyl-3-H-imidazolium), dibasic [C₁C …