MXenes as an emerging class of 2D metallic carbide/carbonitrides materials have great potentials in designing and fabricating functional polymer composites. In this study, Ti3C2Tx as a representative MXene was employed to fabricate thin-film nanocomposite (TFN) membranes. The abundant surface groups (mainly OH) on Ti3C2Tx allowed facile modification, and thus evenly functionalized nanosheets were obtained. Four functional groups were grafted on Ti3C2Tx surface respectively, which was found to strongly affect the affinity towards solvent molecules and further determine the solvent transport properties of membranes. Interestingly, the functional groups on Ti3C2Tx, namely NH2, COOR, C6H6, and C12H26, could effectively enhance the flux for isopropanol, ethyl acetate, toluene, and n-heptane, respectively, no matter the polymer matrix was hydrophilic or hydrophobic. This finding indicated that the task-specific function of Ti3C2Tx could be distinctly transferred to TFN membranes. Moreover, the nanosheets effectively blocked the permeation of solute molecules, resulting in high rejection ability.

Efficient separation of CO2 from other gases has become an issue of world-wide concern. Intrigued by the fascinating carbonic anhydrase-catalysed CO2 hydration and deprotonation in biological organisms, researchers have found that water can play a significant role in fast and selective CO2 transport (e.g. facilitating transport, salting-out effect, swelling, synergic sorption, etc.) and have managed to fabricate super CO2 capture materials by judiciously introducing water into solids. Considering that water usually exists in industrial CO2 resources and often acts as a negative impurity due to competitive sorption and pore blockage, exploring CO2 capture materials with the aid of water has become an important emerging strategy to provide general and excellent paradigms for practical CO2 capture technologies. In this sense, we propose a new concept, “water-facilitated CO2 capture (WFCC) materials”, which refers to solid materials (either adsorbents or membranes) with a remarkable improvement in CO2 capture performance due to entrapped water. In this way, we endeavor to answer an important question: when and how water contributes to this drastic enhancement. Strategies to avoid the negative effects of water and to enable WFCC are also tentatively proposed.

•The concept of acid/base pairs was employed to design anhydrous PEMs.•Polydopamine-modified silica particles were uniformly dispersed in SPEEK membrane.•The membranes displayed enhancement in both stability and anhydrous proton conductivity.Novel anhydrous proton exchange membrane is (PEM) facilely prepared by embedding dopamine-modified silica nanoparticles (DSiOis2) into sulfonated poly (ether ether ketone) (SPEEK) polymer matrix. DSiO2 bearing NH2/NH groups are synthesized inspired by the bioadhesion principle, which are uniformly dispersed within SPEEK membrane due to the good interfacial compatibility. The interfacial electrostatic attractions render unique rearrangement of the nanophase-separated structure and the chain packing of the resultant hybrid membranes. As a result, the thermal and mechanical stabilities as well as structural stability of the hybrid membranes are enhanced when compared to SPEEK control membrane. On the other hand, induced by the attractions, acid–base pairs are formed at the SPEEK/DSiOarewere2 interface, where fast proton transfer via Grotthuss mechanism is expected. These features confer much higher proton conductivities on the DSiO2-filled membranes under both hydrated and anhydrous conditions, compared to those of the SPEEK control membrane and SiO2-filled membranes. Particularly, the hybrid membrane with 15 wt% DSiO2 achieve the highest conductivities of 4.52achieveachieved × 10−3 S cm−1 at 120 °C under anhydrous condition, which is much higher than the SPEEK control membrane and the commercial Nafion membrane (0.1iswas × 10−3 S cm−1). The membrane with 9 wt% DSiO2 show an open cell potential of 0.98showshowed V and an optimum power density of 111.7 mW cm−2, indicative of its potential application in fuel cell under anhydrous condition.

Efficient separation of CO2 from other gases has become an issue of world-wide concern. Intrigued by the fascinating carbonic anhydrase-catalysed CO2 hydration and deprotonation in biological organisms, researchers have found that water can play a significant role in fast and selective CO2 transport (e.g. facilitating transport, salting-out effect, swelling, synergic sorption, etc.) and have managed to fabricate super CO2 capture materials by judiciously introducing water into solids. Considering that water usually exists in industrial CO2 resources and often acts as a negative impurity due to competitive sorption and pore blockage, exploring CO2 capture materials with the aid of water has become an important emerging strategy to provide general and excellent paradigms for practical CO2 capture technologies. In this sense, we propose a new concept, “water-facilitated CO2 capture (WFCC) materials”, which refers to solid materials (either adsorbents or membranes) with a remarkable improvement in CO2 capture performance due to entrapped water. In this way, we endeavor to answer an important question: when and how water contributes to this drastic enhancement. Strategies to avoid the negative effects of water and to enable WFCC are also tentatively proposed.