To achieve sub-angstrom separation of N-methylpyrrolidone and 1,5-dimethyl-2-pyrrolidone, cyclodextrin-derived carbon materials with distinct pore environments and surface functionalities were synthesized via hydrothermal carbonization and high-temperature pyrolysis. Three types of carbons were obtained: non-porous carbons rich in surface functionalities, carbons with both functionalities and microporous structures, and carbons with limited functionalities but diverse micropore environments. Systematic adsorption experiments, supported by density functional theory and molecular dynamics simulations, were conducted to establish the structure–performance relationships. The results demonstrate that surface functionalities alone are insufficient for separation, whereas pore confinement is the decisive factor. A 7.3 Å pore was identified as the optimal confinement space, providing the strongest thermodynamic interactions and the fastest diffusion kinetics, thereby enabling highly selective adsorption of 1,5-dimethyl-2-pyrrolidone from N-methylpyrrolidone. This work not only clarifies the pore formation mechanism of cyclodextrin-derived carbons but also highlights precise pore-size tuning as a paradigm for sub-angstrom molecular separation, offering theoretical guidance for the design of advanced adsorbent materials.

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 6 g of St-V-15 could reduce the Cr(Ⅲ) concentration in a solution containing 1 g of H₃tci from 840 ppb to 27.5 ppb. Furthermore, St-V-15 exhibited a maximum adsorption capacity of 145 mg g⁻¹ calculated using the Langmuir model and a rapid initial adsorption rate of 82.92 mg g⁻¹ min⁻¹ at 333 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 10 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.