Robust, Lightweight, Hydrophobic, and Fire-Retarded Polyimide/MXene Aerogels for Effective Oil/Water Separation

Abstract

Polyimide (PI) aerogels have attracted great attention owing to their low density and excellent thermal stability. However, hydrophobic surface modification is required for PI aerogels to improve their ability in oil/water separation due to their amphiphilic characteristic. Two-dimensional MXenes (transition metal carbides/nitrides) can be utilized as nanofillers to enhance the properties of polymers because of their unique layered structure and versatile interface chemistry. Herein, the robust, lightweight, and hydrophobic PI/MXene three-dimensional architectures were fabricated via freeze-drying of polyamide acid/MXene suspensions and thermal imidization. Polyamide acid was synthesized using N-N-dimethylacetamide and 4,4′-oxydianiline. MXene (Ti3C2T x ) dispersion was obtained via the etching of Ti3AlC2 and ultrasonic exfoliation. Taking advantage of the strong interaction between PI chains and MXene nanosheets, the interconnected, highly porous, and hydrophobic PI/MXene aerogels with low density were fabricated, resulting in the improved compressive performance, remarkable oil absorption capacity, and efficient separation of oil and water. For the PI/MXene-3 aerogel (weight ratio, 5.2:1) without any surface modification, the water contact angle was 119° with a density of 23 mg/cm3. This aerogel can completely recover to its original height after 50 compression–release cycles, exhibiting superelasticity and exceptional fatigue-resistant ability. It also showed high absorption capacities to various organic liquids ranging from approximately 18 to 58 times of their own weight. This hybrid aerogel can rapidly separate the chloroform, soybean oil, and liquid paraffin from the water–oil system. The thermally stable hybrid aerogel also exhibited excellent fire safety properties and outstanding reusability under an extreme environment.

The Recent Advances in the Mechanical Properties of Self-Standing Two-Dimensional MXene-Based Nanostructures: Deep Insights into the Supercapacitor

“…was higher than that of PVA/CNC (241 ± 51 MPa), PVA/Ti 3 C 2 T x (283 ± 60 MPa) , and PVA nanofibers (221 ± 51 MPa) [ 112 ]. Likewise, polyimide/Ti 3 C 2 T x aerogel prepared via the freeze-drying of and annealing to form a robust, lightweight, and hydrophobic aerogel ( Figure 10 a) with three-dimensional “house of cards” structure ( Figure 10 b) [ 113 ]. The compressive strength at 80% strain and Young’s modulus of elasticity for PI/Ti 3 C 2 T x aerogel increased significantly with decreasing the Ti 3 C 2 T x concentration.…”

“…The compressive strength at 80% strain and Young’s modulus of elasticity for PI/Ti 3 C 2 T x aerogel increased significantly with decreasing the Ti 3 C 2 T x concentration. This is owing to greater porosity and lower density of PI/MXene aerogels with the increase of the Ti 3 C 2 T x amount [ 113 ]. Interestingly, the elastic properties, PI/MXene-3 with a ratio of 5.2:1, respectively, showed impressive stress−strain repeatability after 50 cycles of compression-release ( Figure 10 c), attributed to the strong interactions between PI chains and Ti 3 C 2 T x nanosheets in the hybrid aerogel [ 113 ].…”

“…This is owing to greater porosity and lower density of PI/MXene aerogels with the increase of the Ti 3 C 2 T x amount [ 113 ]. Interestingly, the elastic properties, PI/MXene-3 with a ratio of 5.2:1, respectively, showed impressive stress−strain repeatability after 50 cycles of compression-release ( Figure 10 c), attributed to the strong interactions between PI chains and Ti 3 C 2 T x nanosheets in the hybrid aerogel [ 113 ]. Silver nanowires, combined with Ti 3 C 2 T x (AgNWs-Ti 3 C 2 T x ) transparent conductive electrode, displayed a higher conductivity, chemical stability, and mechanical stability than that of pristine AgNW electrode [ 114 ].…”

1D/2D Nanomaterials Synergistic, Compressible, and Response Rapidly 3D Graphene Aerogel for Piezoresistive Sensor

“…Aerogels are lightweight porous solid materials characterized by their extremely low density, high porosity, and high specific surface area. [ 1,2 ] In general, aerogels can be prepared by chemical vapor deposition (CVD), [ 3 ] hydrothermal methods, [ 4 ] and 3D printing, [ 5 ] while they can be prepared form silica, [ 6 ] carbon nanotubes, [ 7 ] graphene, [ 8,9 ] polyimide, [ 10,11 ] Kevlar, [ 12,13 ] and natural materials [ 14–16 ] to name a few. Due to the unique structure and properties of aerogels, they can be utilized for energy storage and conversion, [ 17–19 ] sensors, [ 20,21 ] catalyst support, [ 22,23 ] environmental remediation, [ 24,25 ] and many other diverse applications.…”

MXene Materials for Designing Advanced Separation Membranes

“…The "separation/purification" share of the pie as seen in (b) also includes applications such as capacitive deionization, [48,49] adsorptive or reactive detoxification of water contaminants, [50,51] and oil/ water separation by aerogels. [52] ) synthesis) of Ti 3 AlC 2 , Ti 3 C 2 T x has served as the basis of MXene research to date. [12,32,[57][58][59][60] The most commonly used etchant for MXene synthesis is aqueous hydrofluoric acid (HF).…”