MXene-polymer nanocomposites possess the attractive properties of MXenes and the flexibility and facile processability of polymers. These nanocomposites have shown better properties such as light-to-heat conversion, electromagnetic interference shielding, and charge storage, compared to other nanocomposites. Surface modification allows for changing surface properties of MXenes and for the occurrence of desired chemical reactions (such as polymerization) on MXene flakes. We have studied surface modification of Ti3C2. In one study, we developed and used a simple one-step method of Ti3C2 carboxylation, which decreased the zeta-potential of Ti3C2 by ~16 to ~18 mV over a pH range of 2.0 to 8.5, and improved Ti3C2 stability in the presence of molecular oxygen. Compared to pristine Ti3C2, carboxylated Ti3C2 has a slightly higher but much faster mercury ion uptake, and leaches out less mercury ions. In another study, the surface modification of Ti3C2 with an aminosilane coupling agent changed Ti3C2 surface charge from –35 mV to +25 mV at neutral pH, which allows for in-situ preparation of self-assembled films. The functionalized Ti3C2 has an isoelectric point at a pH around 10.7, and the surface charge of +62 mV at a pH of 2.58. We have studied the embedment of pristine and surface-modified Ti3C2 into different polymers (e.g., Pebax-1657) and have fabricated novel nanocomposite membranes with superior gas-separation performance. Our thin-film Ti3C2-Pebax membranes have CO2/N2 and CO2/H2 separation performances that are above the state-of-the-art and in the target area for cost-efficient CO2 capture ($29/ton of separated CO2).

Ti3C2 MXene surface modification and polymer nanocomposites: Water purification and gas separation

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