Polyaniline-Coated MOFs Nanorod Arrays for Efficient Evaporation-Driven Electricity Generation and Solar Steam Desalination.

Though evaporation-driven electricity generation has emerged as a novel eco-friendly energy and attracted intense interests, it is typically demonstrated in pure water or a very low salt concentration. Integrating evaporation-driven electricity generation and solar steam desalination simultaneously should be more promising. Herein, a polyaniline coated metal-organic frameworks (MOFs) nanorod arrays membrane is synthesized which inherits the merits of both polyaniline and MOFs, demonstrating nice stability, good interfacial solar steam desalination, and evaporation-driven electricity generation. Moreover, an integrated system based on this hybrid membrane achieves good interfacial solar-heating evaporation and prominently enhanced evaporation-driven electricity generation under one sun. Notably, the realization of effective seawater desalination and efficient evaporation-driven electricity generation simultaneously by the non-carbon-based materials is reported for the first time, which provides a new alternative way for cogenerating both freshwater and electricity by harvesting energy from seawater and solar light.

A self-confinement synthesis of a POM-decorated MOF thin film for actively hydrolyzing ethyl acetate.

Hybrid heterogeneous solid acid catalysts polyoxometalate-decorated metal organic framework (POM@MOFs) thin films were synthesized from POMs and metal hydroxide nanostrands via a self-confinement method at room temperature, which show high hydrolyzing activity (1027.5 µmol g-1 min-1) for ethyl acetate with durable stability and an easy recovery. This provides a general way to easily prepare nano POM@MOF thin film catalysts.

Rational design of a Fe/S/N/C catalyst from ZIF-8 for efficient oxygen reduction reaction.

Fe/N/C catalysts have been regarded as prospective electrocatalysts for oxygen reduction reactions (ORR). As reported, doping S into the Fe/N/C catalyst is an effective strategy to further enhance its ORR performance. Herein, a rational design is demonstrated to synthesize Fe/S/N/C catalysts with a flexible ratio of the doped Fe and S. Through atomic substitution and molecular confinement methods, Fe and S were incorporated into the ZIF-8 precursor, respectively. After further pyrolysis, the Fe/S/N/C catalyst was obtained with uniformly dispersed Fe-Nx, C-S-C active sites and high specific surface area. The Fe/S/N/C catalyst shows a high half-wave potential in alkaline medium, nearly 32 mV higher than the commercial Pt/C, owing to the strong synergistic effect from Fe-Nx and C-S-C active sites. Additionally, the Fe/S/N/C catalyst exhibits good long-term electrocatalytic durability and high endurance to methanol crossover, implying it is a suitable candidate to take the place of conventional Pt or Pt-based catalysts in electrochemical devices.

Photothermal-Responsive Microporous Nanosheets Confined Ionic Liquid for Efficient CO2 Separation.

2D materials hold promising potential for novel gas separation. However, a lack of in-plane pores and the randomly stacked interplane channels of these membranes still hinder their separation performance. In this work, ferrocene based-MOFs (Zr-Fc MOF) nanosheets, which contain abundant of in-plane micropores, are synthesized as porous supports to fabricate Zr-Fc MOF supported ionic liquid membrane (Zr-Fc-SILM) for highly efficient CO2 separation. The micropores of Zr-Fc MOF nanosheets not only provide extra paths for CO2 transportation, and thus increase its permeance up to 145.15 GPU, but also endow the Zr-Fc-SILM with high selectivity (216.9) of CO2 /N2 through the nanoconfinement effect, which is almost ten times higher than common porous polymer SILM. Furthermore, based on the photothermal-responsive properties of Zr-Fc MOF, the performance is further enhanced (35%) by light irradiation through a photothermal heating process. This provides a brand new way to design light facilitating gas separation membranes.

Fe3Pt intermetallic nanoparticles anchored on N-doped mesoporous carbon for the highly efficient oxygen reduction reaction.

A facile strategy is proposed to prepare N-doped mesoporous carbon catalysts dispersed with Fe3Pt intermetallics (Fe3Pt/N@C) through direct pyrolysis of Pt-Fe co-functionalized ZIF-8. The catalysts exhibit excellent ORR activity, outstanding mass activity with ultralow Pt loading, low H2O2 yield, and high cycling stability in alkaline medium.

CO2 -Philic Separation Membrane: Deep Eutectic Solvent Filled Graphene Oxide Nanoslits.

CO2 capture and sequestration is an energy-intensive industry to deal with the global greenhouse effect. Membrane separation is considered a cost-effective method to mitigate the emission of CO2 . Though good separation performance and stability have been reported, supported ionic liquid membranes are still not widely applied for CO2 separation due to the high cost. As a novel analogous solvent to ionic liquid, deep eutectic solvent retains the excellent merits of ionic liquid and is cheap with facile preparation. Herein, a highly CO2 -philic separation membrane is constructed by nanoconfining choline chloride/ethylene glycol (ChCl/EG) deep eutectic solvent into graphene oxide nanoslits. Molecular dynamic simulation results indicate that the confinement makes a difference to the structure of the nanoconfined ChCl/EG liquid from their bulk, which remarkably facilitates CO2 transport. By tuning the molar ratio of ChCl/EG and thickness of the membrane, the resultant membrane exhibits outstanding separation performance for CO2 with excellent selectivity over other light gases, good long-term durability, and thermal stability. This makes it a promising membrane for selective CO2 separation.

Simultaneous Recovery of Metal Ions and Electricity Harvesting via K-Carrageenan@ZIF-8 Membrane.

The spent lithium-ion batteries contain significant amounts of valuable metals such as lithium and cobalt. However, how to effectively recover these valuable metals and minimize environmental pollution simultaneously is still a challenge. In this work, a natural biopolymer K-Carrageenan is introduced into a stable metal-organic framework ZIF-8 to form a composite (KCZ) membrane for selectively separating Li+ from Co2+ and simultaneously harvesting the concentration gradient energy efficiently. The prepared KCZ membrane shows an Li+ ionic conductivity of up to 1.70 × 10-5 S cm-1, 5 orders of magnitude higher than 1.1 × 10-10 S cm-1 for pristine ZIF-8, with an Li+ flux of 0.342 mol m-2 h-1 and a selectivity of about 8.29 for Li+ over Co2+. Moreover, this asymmetric KCZ/anodic alumina oxide membrane exhibits a good output power of up to 3.54 µW when employed as a concentration-gradient energy-harvesting device during the separation process. Hence, the KCZ membrane shows great potential in application for advanced separation and simultaneous concentration gradient energy harvesting.

Laminated mica nanosheets supported ionic liquid membrane for CO2 separation.

Mica has attracted great attention due to its excellent photoelectric property and it is mainly used in the optics and electronics area. High-quality mica nanosheets exfoliated from natural ground mica have been successfully achieved recently. It improves the application potential of mica as well as extending the application field to gas separation as a new two-dimensional (2D) material. Herein, we firstly constructed a mica membrane by regularly stacking mica nanosheets and then immobilized ionic liquid (IL) into its 2D channels to separate CO2 from H2, CH4 and N2. Gas diffusion is changed from Knudsen diffusion in the mica membrane to a solution-diffusion mechanism after inserting IL. The resultant membrane, the mica supported IL membrane (M-SILM), has about 80 GPU for CO2 permeance, and selectivity for CO2/H2, CO2/CH4 and CO2/N2 of 7.7, 28.6 and 87, respectively. It is the first time a mica nanosheet to construct a gas separation membrane has been used. As a cheap raw material with facile treating, mica shows promising potential for gas separation and competitiveness among 2D material supported IL membranes.

R-phycoerythrin proteins@ZIF-8 composite thin films for mercury ion detection.

Mercury, as one of the most prevalent toxic metals released by various natural and anthropogenic processes, causes severe pollution of soil and groundwater. In this work, R-phycoerythrin (R-PE) proteins encapsulated into ZIF-8 composite thin films were prepared via a solid-confinement conversion process and applied as fluorescent sensors for mercury ion detection. The R-PE proteins encapsulated into ZIF-8 exhibit dual color emissions including green (518 nm) and red (602, 650 nm) fluorescence, while the original orange emission (578 nm) of pure R-PE is significantly suppressed. R-PE@ZIF-8 presents excellent selectivity and sensitivity for mercury detection in a large pH range without buffer solution. Under the optimal conditions, there is a good linear relationship between the fluorescence quenching efficiencies of R-PE@ZIF-8 and logarithmic concentrations of mercury ions in the range of 0.001-50 µM with the detection limit (LOD) of 6.7 nM much lower than the guideline value given by the World Health Organization. Furthermore, multi-peak detection of R-PE@ZIF-8 improves the detection accuracy of Hg2+ concentration.

Hierarchical Porous SWCNT Stringed Carbon Polyhedrons and PSS Threaded MOF Bilayer Membrane for Efficient Solar Vapor Generation.

Interfacial solar vapor generation is considered to be an efficient and eco-friendly technology for harvesting solar energy and providing freshwater. However, the efficient and long-term steady evaporation of seawater under 1 sun becomes a critical issue when it comes to practical applications. Based on this issue, a special double-layer structure, which contains a metal-organic-framework-derived hierarchical porous carbon membrane (HPCM) for solar absorption and a polystyrene sulfonate (PSS)@Cu3 (BTC)3 •3H2 O (HKUST-1)/single-walled carbon nanotube (SWCNT) (PHS) membrane for water supply and salt blocking, is designed in this work. The converted heat is utilized efficiently in situ to drive the evaporation of water-trapped HPCM. The PHS membrane with PSS modified channels successfully prevents the deposition of salt. Due to the synergistic combination of the HPCM and PHS membranes, the device exhibits a remarkably high water evaporation rate of 1.38 kg m-2 h-1 and solar-vapor generation efficiency of 90.8% under 1 sun.

Dual emission from nanoconfined R-phycoerythrin fluorescent proteins for white light emission diodes.

A facile strategy to encapsulate R-phycoerythrin (R-PE) proteins and CdSe x S1-x /ZnS quantum dots (QDs) in ZIF-8 thin films is developed through a one-pot solid-confinement conversion process. The resultant R-PE/CdSe x S1-x /ZnS@ZIF-8 thin film exhibits high-quality white light emission and good thermal stability up to 80 °C.

Highly conductive PEDOT:PSS threaded HKUST-1 thin films.

Highly conductive PEDOT:PSS threaded HKUST-1 thin films with high porosity were prepared. The highest conductivity of these films was 13 S cm-1, nine orders of magnitude greater than that of pristine HKUST-1. A PEDOT:PSS threaded HKUST-1 thin film with 20 wt% PEDOT:PSS exhibits 300 times enhancement of the electrochemical performance of pristine HKUST-1 when applied as an electrode for thin-film-like supercapacitors.

Phase-Dependent Fluorescence Quenching Efficiency of MoS2 Nanosheets and Their Applications in Multiplex Target Biosensing.

Two-dimensional layered transition-metal dichalcogenide nanosheets have shown great potential in biosensors owing to their unique properties. Here, we exfoliated ultrathin metallic and semiconductive MoS2 nanosheets based on a chemical exfoliation method. We compared the difference of fluorescence quenching efficiency between metallic and semiconductive MoS2 nanosheets. We found that the fluorescence quenching efficiency of MoS2 nanosheets is phase-dependent. The ultrathin metallic MoS2 nanosheets with larger contents of a 1T-phase structure show higher fluorescence quenching efficiency than semiconductive MoS2 nanosheets, which can be ascribed to the higher conductivity of metallic MoS2 nanosheets. On the basis of the excellent fluorescence quenching efficiency of metallic MoS2 nanosheets and their discriminative adsorption toward single-strand DNA and double-strand DNA, a fluorescent biosensor for multiplex detection of DNA was developed. This fluorescent biosensing platform allows simultaneous fluorescence quenching of two single-strand DNA probes labeled with different fluorophores, resulting in multiplex detection of different DNA sequences in one homogeneous solution with high sensitivity.

Ionic Liquid Selectively Facilitates CO2 Transport through Graphene Oxide Membrane.

Membrane separation of CO2 from H2, N2, or CH4 has economic benefits. However, the trade-off between selectivity and permanence in membrane separation is challenging. Here, we prepared a high-performance CO2-philic membrane by confining the [BMIM][BF4] ionic liquid to the nanochannels in a laminated graphene oxide membrane. Nanoconfinement causes the [BMIM][BF4] cations and anions to stratify. The layered anions facilitate CO2 transportation with a permeance of 68.5 GPU. The CO2/H2, CO2/CH4, and CO2/N2 selectivities are 24, 234, and 382, respectively, which are up to 7 times higher than that of GO-based membranes and superior to the 2008 Robeson upper bound. Additionally, the resultant membrane has a high-temperature resistance, long-term durability, and high-pressure stability, indicating its great potential for CO2 separation applications. Nanoconfining an ionic liquid into the two-dimensional nanochannels of a laminated membrane is a promising gas separation method and a nice system for investigating ionic liquid behavior in nanoconfined environments.

Enhanced Gas Separation through Nanoconfined Ionic Liquid in Laminated MoS2 Membrane.

Two-dimensional (2D) materials-based membranes show great potential for gas separation. Herein an ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), was confined in the 2D channels of MoS2-laminated membranes via an infiltration process. Compared with the corresponding bulk [BMIM][BF4], nanoconfined [BMIM][BF4] shows an obvious incremental increase in freezing point and a shift of vibration bands. The resulting MoS2-supported ionic liquid membrane (MoS2 SILM) exhibits excellent CO2 separation performance with high CO2 permeance (47.88 GPU) and superb selectivity for CO2/N2 (131.42), CO2/CH4 (43.52), and CO2/H2 (14.95), which is much better than that of neat [BMIM][BF4] and [BMIM][BF4]-based membranes. The outstanding performance of MoS2 SILMs is attributed to the nanoconfined [BMIM][BF4], which enables fast transport of CO2. Long-term operation also reveals the durability and stability of the prepared MoS2 SILMs. The method of confining ILs in the 2D nanochannels of 2D materials may pave a new way for CO2 capture and separation.

Hierarchical Mesoporous Metal-Organic Frameworks for Enhanced CO2 Capture.

Hierarchical porous materials are promising for catalyst, separation and sorption applications. A ligand-assisted etching process is developed for template-free synthesis of hierarchical mesoporous MOFs as single crystals and well-intergrown membranes at 40 °C. At 223 K, the hierarchical porous structures significantly improve the CO2 capture capacity of HKUST-1 by more than 44 % at pressures up to 20 kPa and 13 % at 100 kPa. Even at 323 K, the enhancement of CO2 uptake is above 25 % at pressures up to 20 kPa and 7 % at 100 kPa. The mesoporous structures not only enhance the CO2 uptake capacity but also improve the diffusion and mass transportation of CO2 . Similarly, well-intergrown mesoporous HKUST-1 membranes are synthesized, which hold the potential for film-like porous devices. Mesoporous MOF-5 crystals are also obtained by a similar ligand-assisted etching process. This may provide a facile way to prepare hierarchical porous MOF single crystals and membranes for wide-ranging applications.