High-performance CO2 separation membranes: comparison of graphene oxide and carboxylated graphene oxide nanofillers

As an emerging nanomaterial, graphene oxide (GO) has gained a special interest in the field of nanocomposite membranes for gas separation. However, its agglomeration within the polymer matrix inhibits its beneficial effects. In the present study, the effect of increased oxygenated groups of GO on its agglomeration tendency and the gas separation properties of the resultant mixed matrix membrane (MMM) was investigated for the first time. GO and carboxylated GO (GO-COOH) were incorporated into polysulfone (PSU), and the two types of membranes were compared in terms of nanofiller dispersion, chemical and crystalline structure, tensile and thermal properties, and CO2/CH4 separation. The homogenous dispersion of GO-COOH compared to GO led to the higher tensile strength, elastic modulus, and thermal stability of the MMM. The PSU/GO-COOH membrane at an optimal nanofiller concentration exhibited significantly higher CO2 permeability and CO2/CH4 selectivity in both pure and mixed gas experiments. Using CO2/CH4 mixed gas with a 40/60 volume ratio, the PSU/0.2% GO-COOH membrane provided a permeability of 55.20 barrer and a CO2 selectivity of 280.20, which were almost 18 and 29 times, respectively, higher than those of the neat PSU membrane. The performance of the mentioned membrane was significantly superior to those of the previous literature and surpassed the 2019-updated Robeson upper bound.

Automated summary

This study investigated the effect of increased oxygenated groups of graphene oxide (GO) on its agglomeration tendency and gas separation properties of mixed matrix membranes (MMMs). It was found that carboxylated GO (GO-COOH) exhibited better dispersion compared to GO, leading to higher tensile strength, elastic modulus, and thermal stability of the MMM. The PSU/0.2% GO-COOH membrane showed significantly improved CO2 permeability and CO2/CH4 selectivity, surpassing previous literature and the 2019-updated Robeson upper bound.