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

Abstract

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.