Enhanced interaction of CO2 with TCNQ-modified CuO nanoparticle-infused PEO matrix: A novel approach in gas transport technology

Abstract

We developed a composite membrane based on polyethylene oxide (PEO), achieving high CO2 selectivity, by incorporating 7,7,8,8-tetracyanoquinodimethane (TCNQ)-modified CuO nanoparticles into the PEO matrix. The addition of TCNQ helps in evenly distributing the CuO nanoparticles throughout the membrane, preventing them from clumping together. This treatment not only enhances the dispersion of CuO particles but also imparts a positive charge to their surface, which is beneficial for increasing the selectivity for CO2 over N2. The extent of this surface charge modification on the CuO nanoparticles was evaluated using X-ray photoelectron spectroscopy (XPS), while the synergy between the polymer and the additives was verified through Fourier-transform infrared (FT-IR) spectroscopy studies. The combination of CuO nanoparticles in the membrane contributes to both barrier and carrier effects, enhancing the gas selectivity. This is further aided by the intrinsic properties of PEO, a rubber-like polymer known for its good gas permeance. As a result of these combined effects, the PEO/CuO/TCNQ membrane exhibited a remarkable CO2 selectivity of 393 and a CO2 permeance of 3.9 gas permeation unit (GPU). The superior separation performance of this membrane can be ascribed to three main factors: enhanced solubility due to the oxide layer on the particle surfaces and in the polymer matrix, improved transport efficiency via reversible interactions thanks to the positively charged surface, and the effective barrier provided by the nanoparticles against N2 transport. These findings are expected to contribute significantly to future studies on the surface modification of metal nanoparticles and in the field of gas separation membranes.