Tailoring MnO2 nanodomains in organic-inorganic hybrid interfaces toward tunable hydrocarbon separation

Organic solvent nanofiltration offers an energy-saving alternative to distillation for hydrocarbon fractionation. Here, we introduce a simple and scalable method for fabricating novel organic-inorganic hybrid membranes from polybenzimidazole (PBI) and manganese oxide (MnO₂), designed for the separation of complex hydrocarbons. Homogeneously integrated MnO₂ domains, formed via oxidative interaction with imidazole moieties within the PBI matrix, create a rigid hybrid structure with enhanced molecular selectivity. By systematically tuning PBI concentration, KMnO₄ dosage, and reaction time, we achieved membranes with low molecular weight cut-off (MWCO) as low as 266 g mol⁻¹. Notably, these membranes surpassed the reported upper bound for toluene/1,3,5-triisopropylbenzene separation and demonstrated effective fractionation of complex hydrocarbon mixtures, such as naphtha, enriching the lighter fractions. This study clarifies the role of KMnO₄ in PBI modification: rather than inducing direct N–N crosslinking as previously suggested, it facilitates the in situ generation of crystalline MnO₂ domains that bolster membrane rigidity and molecular selectivity. These findings underscore the potential of hybrid PBI membranes as a practical platform for membrane-assisted crude oil fractionation and offer prospects for advanced energy-efficient separation strategies.