Deciphering Adsorption Selectivity of Styrene/Ethylbenzene: The Critical Role of Nitrogen‐Engineered Electrostatic Potential in MOF

Energy‐efficient purification of styrene (ST) from ethylbenzene (EB) remains a formidable challenge due to their striking molecular similarity, demanding advanced separation technologies beyond conventional extractive distillation. Herein, we present an electrostatic potential (ESP) engineering strategy achieving molecular recognition within metal–organic frameworks (MOFs). By incorporating a single nitrogen atom into the isophthalate linker of CAU‐10, forming CAU‐10‐pydc, we generate spatially organized negative ESP sites within the channels. This modification significantly enhances interactions with the vinyl C─H groups of ST while concurrently attenuating the binding of EB. Consequently, CAU‐10‐pydc demonstrates a remarkable increase in both ST adsorption capacity and selectivity. Comprehensive adsorption experiments, breakthrough measurements, and calorimetry reveal the superior ST affinity of CAU‐10‐pydc, achieving a 49.1% enhancement in dynamic vapor‐phase selectivity and superior liquid‐phase performance compared to its parent framework. Density functional theory (DFT) calculations and in situ Fourier transform infrared (FTIR) spectroscopy elucidate that cooperative C─H···N, C─H···O, and N···π interactions are the mechanistic underpinnings for the preferential trapping of ST within the nitrogen‐engineered pores. This work establishes ESP tailoring as a potent and applicable avenue for the purification of ST/EB mixtures, and more broadly for differentiating molecules with subtle steric variations but distinct charge distributions.