Carbonization of Carboxylate-Functionalized Polymers of Intrinsic Microporosity for Water Treatment

Considering the variations in their pore characteristics and heterogeneity, the carbonization process of carboxylate-functionalized polymers of intrinsic microporosity (PIM-COOH) is investigated and the resulted membranes are tested for water treatment. The four distinct types of sub-nanosized membranes with different oxygen-to-carbon ratios are prepared at four different temperatures: the pristine polymer membrane, crosslinked membrane via thermal decarboxylation, amorphous carbon membrane, and graphitic carbon membrane. Notably, the sub-1 nm micropores of all the heat-treated samples that do not exhibit a broadening pore size distribution are still retained. Nanofiltration performance is investigated using an aqueous MgSO₄ solution (2000 ppm), pure water, and a series of the defect-free, sub-1 nm microporous membranes. While retaining the salt rejection, the water flux of the membranes increases with the pyrolysis temperature owing to their low friction property.