Engineering sulfonated polymers for the removal of ultra-trace complexed Cr(III) in tris(2-carboxyethyl) isocyanurate photoresist resin monomers

The semiconductor manufacturing industry imposes stringent requirements on the metal ion content of photoresist resin monomers. Tris(2-carboxyethyl) isocyanurate (H3tci), a critical raw material for photoresist resin monomers, inevitably incorporates metal ions during production. However, its inherent carboxyethyl groups form stable coordination complexes with Cr(III), hindering the semiconductor-grade resin monomer production. To achieve the ultra-deep removal of Cr(III) at ultra-trace concentrations, inspired by the Hard-Soft-Acid-Base theory, we systematically modulated the electron-rich sulfonic acid group on polymers via controlled sulfonation conditions to achieve a novel series of adsorption materials (St) with ultra-high Cr(III) adsorption affinity. The adsorption-recrystallization process using our St-V-15, which exhibited the benchmarked distribution coefficient (Kd) of 1.01×108 mL g-1, could reduce Cr(III) concentration in H3tci from 840 ppb to 24.3 ppb. Furthermore, St-V-15 exhibited a maximum adsorption capacity calculated using the Langmuir model of 126 mg g-1 and a rapid initial adsorption rate of 13.58 mg g-1 min-1 at 298 K. Additionally, St-V-15 demonstrated exceptional selectivity for Cr(III) over competing ions (e.g., K(I), Mg(II), Na(I) and Zn(II)) and maintained stable performance over at least 5 adsorption-desorption cycles. The superior performance originated from the chelation between Cr(III) and the sites of O atoms (S-O and S=O) combined with the electrostatic interaction between deprotonated sulfonic acid groups and Cr(III). These results position St-V-15 as a promising adsorption material for ultra-trace Cr(III) removal in H3tci, offering a cost-effective solution for semiconductor-grade resin monomer production for the very first time.