Symbiotic defect-reinforced bimetallic MOF-derived fiber components for solar-assisted atmospheric water collection.

Conversion of atmospheric water to sustainable and clean freshwater resources through MOF-based adsorbent has great potential for the renewable environmental industry. However, its daily water production is hampered by susceptibility to agglomeration, slow water evaporation efficiency, and limited water-harvesting capacity. Herein, a solar-assisted bimetallic MOF (BMOF)-derived fiber component that surmounts these limitations and exhibits both optimized water-collect capacity and short adsorption-desorption period is proposed. The proposed strategy involves utilizing bottom-up interface-induced assembly between carboxylated multi-walled carbon nanotube and hygroscopic BMOF on a multi-ply glass fiber support. The designed BMOF (MIL-100(Fe,Al)-3) skeleton constructed using bimetallic-node defect engineering exhibits a high specific surface area (1,535.28 m2/g) and pore volume (0.76 cm3/g), thereby surpassing the parent MOFs and other reported MOFs in capturing moisture. Benefiting from the hierarchical structure of fiber rods and the solar-driven self-heating interface of photothermal layer, the customized BMOF crystals realize efficient loading and optimized water adsorption-desorption kinetics. As a result, the resultant fiber components achieve six adsorption-desorption cycles per day and an impressive water collection of 1.45 g/g/day under medium-high humidity outdoor conditions. Therefore, this work will provide new ideas for optimizing the daily yield of atmospheric water harvesting techniques.

A Functionally Asymmetric Janus Hygro-Photothermal Hybrid for Atmospheric Water Harvesting in Arid Regions.

Metal-organic frameworks (MOFs) are high-performance adsorbents for atmospheric water harvesting but have poor water-desorption ability, requiring excess energy input to release the trapped water. Addressing this issue, a Janus-structured adsorbent with functional asymmetry is presented. The material exhibits contrasting functionalities on either face - a hygroscopic face interfaced with a photothermal face. Hygroscopic aluminum fumarate MOF and photothermal CuxS layers are in-situ grown on opposite sides of a Cu/Al bimetallic substrate, resulting in a CuxS-Cu/Al-MOF Janus hygro-photothermal hybrid. The two faces serve as independent "factories" for photothermal conversion and water adsorption-desorption respectively, while the interfacing bimetallic layer serves as a "heat conveyor belt" between them. Due to the high porosity and hydrophilicity of the MOF, the hybrid exhibits a water-adsorption capacity of 0.161 g g-1 and a fast adsorption rate (saturation within 52 min) at 30% relative humidity. Thanks to the photothermal CuxS, the hybrid can reach 71.5 °C under 1 Sun in 20 min and desorb 97% adsorbed water in 40 min, exhibiting a high photothermal conversion efficiency of over 90%. CuxS-Cu/Al-MOF exhibits minimal fluctuations after 200 cycles, and its water-generation capacity is 3.21 times that of powdery MOF in 3 h in a self-designed prototype in one cycle.

Bimetallic MOF-Derived Solar-Triggered Monolithic Adsorbent for Enhanced Atmospheric Water Harvesting.

The development of economical, energy-saving, and efficient metal-organic framework (MOF)-based adsorbents for atmospheric water collection is highly imperative for the rapid advancement of renewable freshwater resource exploitation. Herein, a feasible one-step solvothermal formation strategy of bimetallic MOF (BMOF) is proposed and applied to construct a solar-triggered monolithic adsorbent for enhanced atmospheric water collection. Benefiting from the reorganization and adjustment of topology structure by Al atoms and Fe atoms, the resultant BMOF(3) consisting of Al-fumarate and MIL-88A has a higher specific surface area (1202.99 m2  g-1 ) and pore volume (0.51 cm3  g-1 ), thereby outperforming the parental MOFs and other potential MOFs in absorbing water. Expanding upon this finding, the solar-triggered monolithic adsorbent is further developed through a bottom-up assembly of polyaniline/chitosan layers and hybridized BMOF(3) skeletons on a glass fiber support. The resultant monolithic adsorbent exhibits superior sorption-desorption kinetics, leading to directional water transport and rapid solar-assisted vapor diffusion. As a proof-of-concept demonstration, an exquisite water harvester is constructed to emphasize a high water yield of 1.19 g g-1 per day of the designed monolithic adsorbent. Therefore, the design and validation of bimetallic MOF-derived solar-triggered adsorbent in this work are expected to provide a reference for the large-scale applications of MOF-based atmospheric water harvesting.

Characterization of MgCl2·6H2O-Based Eutectic/Expanded Perlite Composite Phase Change Material with Low Thermal Conductivity.

The melting points of the phase change materials (PCMs) incorporated into the walls of buildings should be within the human thermal comfort temperature range. In this paper, 15 wt.% of MgCl2·6H2O was mixed with CaCl2·6H2O to obtain the eutectic with a melting point of 23.9 °C. SrCl2·6H2O suppresses the supecooling of the eutectic. The combination with expanded perlite (EP) via the impregnation method overcomes the phase separation and liquid leakage of the CaCl2∙6H2O-MgCl2∙6H2O mixture. The composite PCM is form-stable with the maximum loading mass fraction up to 50 wt.% and latent heat of 73.55 J/g. EP also significantly reduces the thermal conductivity of the CaCl2∙6H2O-MgCl2∙6H2O from 0.732 to 0.144 W/(m·K). The heating-cooling cycling test reveals that the composite PCM is thermally stable. The cheap eutectic salt hydrate, with little supercooling, no phase separation and liquid leakage, low thermal conductivity and good thermal reliability, show great potential as envelope materials to save energy consumption in buildings.

Effects of electric field on micro-scale flame properties of biobutanol fuel.

With the increasing need of smaller power sources for satellites, energy systems and engine equipment, microcombustion pose a potential as alternative power source to conventional batteries. As the substitute fuel source for gasoline, biobutanol shows more promising characteristics than ethanol. In this study, the diffusion microflame of liquid biobutanol under electric field have been examined through in-lab experiment and numerical simulation. It is found that traditional gas jet diffusion flame theory shows significant inconsistency with the experimental results of micro scale flame in electric field. The results suggest that with the increase of electric field intensity, the quenching flow rate decrease first and increase after it reach its minimum, while the flame height and highest flame temperature increase first and drop after its peak value. In addition, it was also observed that the flame height and highest temperature for smaller tube can reach its maximum faster. Therefore, the interaction between microscale effect and electric field plays a significant role on understanding the microcombustion of liquid fuel. Therefore, FLUENT simulation was adopted to understand and measure the impacts of microflame characteristic parameters. The final numerical results are consistent with the experimental data and show a high reliability.

Preparation, Mechanical and Thermal Properties of Cement Board with Expanded Perlite Based Composite Phase Change Material for Improving Buildings Thermal Behavior.

Here we demonstrate the mechanical properties, thermal conductivity, and thermal energy storage performance of construction elements made of cement and form-stable PCM-Rubitherm® RT 28 HC (RT28)/expanded perlite (EP) composite phase change materials (PCMs). The composite PCMs were prepared by adsorbing RT28 into the pores of EP, in which the mass fraction of RT28 should be limited to be no more than 40 wt %. The adsorbed RT28 is observed to be uniformly confined into the pores of EP. The phase change temperatures of the RT28/EP composite PCMs are very close to that of the pure RT28. The apparent density and compression strength of the composite cubes increase linearly with the mass fraction of RT28. Compared with the thermal conductivity of the boards composed of cement and EP, the thermal conductivities of the composite boards containing RT28 increase by 15%-35% with the mass fraction increasing of RT28. The cubic test rooms that consist of six boards were built to evaluate the thermal energy storage performance, it is found that the maximum temperature different between the outside surface of the top board with the indoor temperature using the composite boards is 13.3 °C higher than that of the boards containing no RT28. The thermal mass increase of the built environment due to the application of composite boards can contribute to improving the indoor thermal comfort and reducing the energy consumption in the buildings.