Water-harvesting Materials Research Articles

MOF-801 enabled rapid-cycling atmospheric water harvester with vertically aligned photothermal channel

Sorption-based atmospheric water harvesting (SAWH) with metal–organic frameworks (MOFs) offer a promising solution to freshwater scarcity in arid regions. However, given the powder nature of MOFs, scaling-up such a concept with industrially favorable monolithic MOFs in bulky sizes remains challenging. In this study, a pore vertically aligned nanocomposite sorbent where MOF-801 is anchored at the polymeric structure surface was prepared via Fe3+-induced crosslinking and directional freezing methods. The continuous vertically aligned hierarchical pores not only offer sufficient sites for MOF-801 loading but also provide rapid moisture transport channels, as well as high solar-thermal conversion efficiency, resulting in a rapid ab/desorption duration of 2 h (including an absorption process for 1 h and a desorption process for 1 h under 1 sun irradiation) and multicycle daily water production of 1.40 L kg−1 at low RH of 20 % and 5.57 L kg−1 at higher RH of 80 %, respectively, which is outperformed most of the state-of-the-art MOFs based SAWH materials. This work provides a simple and effective way to shorten MOF-801 ab/desorption duration, which has great means for designing of high-performance solar-driven water harvesting materials.

Tailoring the covalent organic frameworks based polymer materials for solar-driven atmospheric water harvesting

Atmospheric water harvesting through reticular materials is an innovation that has the potential to change the world. Here, this study offers a technique for creating a solar-powered hygroscopic polymer material for atmospheric water harvesting with the reticular materials. The results show that the porous hygroscopic polymer materials can achieve high performance with high vapor capture (up to ac. 28.8–49.7 mg/g at 28–38 %RH and 25 ℃), rapid photothermal conversion efficiency (up to 32.2 ℃ within 15 min under 1000 W/m−2 light at 25 ℃), a low desorption temperature (lower than 40 ℃), and an effective water release rate. Besides, the material also has excellent water-retention properties, which can effectively store desorbed liquid water in polymer networks for use by vegetation during water demand periods. The strategy opens new avenues for atmospheric water-harvesting materials, which will hopefully solve the global crisis of freshwater shortages.

Preparation and properties of a metal-organic frameworks polymer material based on Sa-son seed gum capable of simultaneously absorbing liquid water and water vapor

Atmospheric water harvesting (AWH) technology has attracted significant attention as an effective strategy to tackle the global shortage of freshwater resources. Work has focused on the use of hydrogel-based composite adsorbents in water harvesting and water conservation. The approaches adopted to make use of hygroscopic inorganic salts which subject to a “salting out” effect. In this study, we report the first use of modified UIO-66-NH2 as a functional steric cross-linker and Sa-son seed gum was used as polymeric substrate to construct super hygroscopic hydrogels by free radical copolymerization. The maximum water uptake on SMAGs (572 cm3·g−1) outperforms pure UIO-66-NH2 (317 cm3·g−1). Simultaneously, our first attempt to use it for anti-evaporation applications in an arid environment (Lanzhou, China) simulating sandy areas. The evaporation rate of the anti-evaporation material treated with 0.20 % super moisture-absorbent gels (SMAGs) decreased by 6.1 % over 64 h period under natural condition in Lanzhou, China. The prepared material can not only absorb liquid water but also water vapor, which can provide a new way for water collection and conservation technology. The design strategy of this material has wide applications ranging from atmospheric water harvesting materials to anti-evaporation technology.

Dehydrated Biomimetic Membranes with Skinlike Structure and Function.

Novel vapor-permeable materials are sought after for applications in protective wear, energy generation, and water treatment. Current impermeable protective materials effectively block harmful agents but trap heat due to poor water vapor transfer. Here we present a new class of materials, vapor permeable dehydrated nanoporous biomimetic membranes (DBMs), based on channel proteins. This application for biomimetic membranes is unexpected as channel proteins and biomimetic membranes were assumed to be unstable under dry conditions. DBMs mimic human skin's structure to offer both high vapor transport and small molecule exclusion under dry conditions. DBMs feature highly organized pores resembling sweat pores in human skin, but at super high densities (>1012 pores/cm2). These DBMs achieved exceptional water vapor transport rates, surpassing commercial breathable fabrics by up to 6.2 times, despite containing >2 orders of magnitude smaller pores (1 nm vs >700 nm). These DBMs effectively excluded model biological agents and harmful chemicals both in liquid and vapor phases, again in contrast with the commercial breathable fabrics. Remarkably, while hydrated biomimetic membranes were highly permeable to liquid water, they exhibited higher water resistances after dehydration at values >38 times that of commercial breathable fabrics. Molecular dynamics simulations support our hypothesis that dehydration induced protein hydrophobicity increases which enhanced DBM performance. DBMs hold promise for various applications, including membrane distillation, dehumidification, and protective barriers for atmospheric water harvesting materials.

Fog harvesting efficiency analysis of biomimicking surfaces: A review

With a rapidly increasing population, pollution levels and industrial water and energy demand are on a constant rise in the past century. Populations residing in arid and semi-arid regions have been victims of water shortage issues since decades. Efficient water harvesting techniques are becoming highly significant today for ensuring the availability of essential resources throughout the globe. Inspired from nature where certain creatures have attractive surfaces which can collect water from the fog or mist even in no rainfall conditions, researchers have developed high-efficient novel water harvesting materials that could effectively address water scarcity issues. Through an in-depth analysis of the wettability and water droplet transportation of these creatures in nature, novel bionic surfaces that combine desirable natures and properties have been developed through innovative fabrication and coupling techniques. This could achieve 2.5 to 5.3 times more efficient water harvesting than conventional superhydrophobic and superhydrophilic surfaces. The efficiency value increased by 250% to 600% by merging different morphologies like Desert beetle, cactus and Janus, compared to their individual uniform morphology surfaces. The review also presents current challenges and scope for future development in water harvesting materials.

Monitoring water harvesting in metal-organic frameworks, one water molecule at a time.

Metal-organic frameworks (MOFs) have gained prominence as potential materials for atmospheric water harvesting, a vital solution for arid regions and areas experiencing severe water shortages. However, the molecular factors influencing the performance of MOFs in capturing water from the air remain elusive. Among all MOFs, Ni2X2BTDD (X = F, Cl, Br) stands out as a promising water harvester due to its ability to adsorb substantial amounts of water at low relative humidity (RH). Here, we use advanced molecular dynamics simulations carried out with the state-of-the-art MB-pol data-driven many-body potential to monitor water adsorption in the three Ni2X2BTDD variants as a function of RH. Our simulations reveal that the type of halide atom in the three Ni2X2BTDD frameworks significantly influences the corresponding molecular mechanisms of water adsorption: while water molecules form strong hydrogen bonds with the fluoride atoms in Ni2F2BTDD, they tend to form hydrogen bonds with the nitrogen atoms of the triazolate linkers in Ni2Cl2BTDD and Ni2Br2BTDD. Importantly, the large size of the bromide atoms reduces the void volume in the Ni2Br2BTDD pores, which enable water molecules to initiate an extended hydrogen-bond network at lower RH. These findings not only underscore the prospect for precisely tuning structural and chemical modifications of the frameworks to optimize their interaction with water, but also highlight the predictive power of simulations with the MB-pol data-driven many-body potential. By providing a realistic description of water under different thermodynamic conditions and environments, these simulations yield unique, molecular-level insights that can guide the design and optimization of energy-efficient water harvesting materials.

Harvesting of Atmospheric Water Using Polymer‐Based Hybrid Hydrogels

AbstractAtmospheric water harvesting (AWH) is an important parallel or supplemental freshwater production technique to liquid water resource‐based technologies due to the availability of moisture resources regardless of location and the possibility of realizing decentralized applications. Recent developments to regulate the characteristic features and nanostructures of moisture‐harvesting materials demonstrate new opportunities to improve device efficiency. Focusing on the design of water harvesting materials and the optimization of the overall system, this review sums up the most recent developments in this area and presents prospects for the future development of AWH. An overview of the processes involved in water sorption by various sorbents and the characteristics and functionality of the polyaniline‐based hydrogels developed for AWH is given. Newly reported hydrogel sorbents used for AWH are evaluated, focusing on their benefits, drawbacks, and design methodologies. Several AWH‐specific water harvesters are described and the impact of the system's mass and heat transfer on its operational effectiveness is explored. Finally, potential roadmaps for the development of this technology are detailed and the challenges in this subject from both a basic research and practical application perspective are discussed.

Fabrication of biomimetic laser etched superwetting copper surfaces for highly improved mist collection efficiency

Water scarcity has become a serious global issue due to frequent global climate extremes such as warming, storms, floods and droughts. Developing highly efficient water-harvesting materials to collect freshwater from mist is a potential solution to solving the issue. Herein, a series of superwetting copper materials with excellent mist collecting efficiencies were successfully prepared via facile etching, modification, laser-scanning and plating methods. The sample surfaces showed unique wettability and structure characteristics that numbers of hydrophilic humps were regularly arrayed and embed into the superhydrophobic surface with nanorod structures. The surface structure, chemical composition of the superwetting copper materials were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. Excellent mist collection efficiency of the fabricated superwetting copper materials was verified by mist collection tests. In addition, the enhancing mechanism of mist collecting behavior on the superwetting copper surface was analyzed. The excellent mist collecting performance of the prepared surfaces exhibited promising potential to achieve mist collecting materials.

Surfaces with modified morphology and wettability arrangement: a potential medium for water harvesting in desertification areas

Abstract The cost of water transport for irrigating drought-endurable plants in desertification areas makes it important to develop other water sources. Research shows that freshwater produced by dewing could satisfy the water requirement during germination of desert plants, therefore, functional materials that promote dew formation provide solutions for reduction of plant irrigation costs in desertification regions. In this review, feasibility of utilizing trace irrigation for ensuring survival of desert plants has been demonstrated. The technologies of preparing water harvesting materials with modified microstructure and wettability arrangement have been introduced, it has been shown that surface embedded with a bump array which has counter wettability compared with its plane section is a common morphology adopted by current works. After comparing climates in desertification regions with those in dewing chambers, it has been found that currently, the expected values of dew productivities of most water harvesting materials in deserted areas will not be as efficient as they performed in experiments due to low relative humidity. However, hydrophobic surface with submicron scale hydrophilic spherical cavity array produced by nanosphere lithography has shown reliable prospects in reducing the energy barrier of heterogeneous nucleation and thus become a more potential medium in dew water production.

Starch-derived photoresponsive high-efficientcy hygroscopic hydrogel for all-weather atmospheric water harvesting

Atmospheric water harvesting (AWH) technology, a new strategy to address the scarcity of fresh water, can be used to collect water from ambient air to produce clean water. Materials with moisture absorption-desorption capabilities are the key to AWH technology. Therefore, this paper reports a starch-derived photoresponsive atmospheric water-harvesting material with an acrylic acid (AA)/acrylamide (AM)-grafted starch hydrogel as the backbone, carboxylated carbon nanotubes (FCNTs) as the solar absorber, and lithium chloride (LiCl) as the water absorber. It was found that the hydrogel had good hygroscopicity in the relative humidity range of 25%–90%, and the adsorption capacity reached 8.5 g g−1 at 90% relative humidity. This hydrogel could recycle collected water vapor, and its performance and economy were found to be better than those of most reported atmospheric water harvesting materials. This material is driven by solar energy to release adsorbed water, and more than 94% of the adsorbed water was released quickly over a wide solar intensity range of 0.5–2 kW m−2. When used in the natural environment during the night/day cycle, this hydrogel was reversibly hygroscopic and achieved clean water production. This highlights the potential of biopolymers for atmospheric water harvesting applications.

Multi-bioinspired hierarchical Janus membrane for fog harvesting and solar-driven seawater desalination

Harvesting water from fog as well as the ocean provides an efficient and sustainable solution for producing clean drinking water. Till now, many different water harvesting materials have been widely reported, however these materials are often only applicable to a single scenario. Inspired by nature, here a novel hierarchical multi-biomimetic membrane is introduced. The mesh-like membrane is composed of polyurethane nanofibers with hydrophilic carbon nanospheres and carbon nanotubes anchored on the surface. It can not only be used to collect fog in the fog flow, but also can be used for photothermal evaporation under the driving of sunlight to collect water. The water harvesting efficiency of this membrane can reach 1666.2 mg cm−2 h−1, the evaporation rate of natural seawater can reach 1.05 kg m−2 h−1 under 1 sun, moreover it is reusable to realize long lasting efficient water harvesting. At present, there are few reports about the structural characteristics of biomimetic termites and fungi and the combination of carbon nanomaterials and polymer nanofibers for the construction of multi macro-micro-nanostructures for water harvesting. Therefore, this research can broaden the way of making biomimetic water harvesting materials in the future and provide new inspiration for the sustainable production of clean water.

Recent Development of Atmospheric Water Harvesting Materials: A Review.

The lack of freshwater has been threatening many people who are living in Africa, the Middle East, and Oceania, while the discovery of freshwater harvesting technology is considered a promising solution. Recent advances in structured surface materials, metal-organic frameworks, hygroscopic inorganic compounds (and derivative materials), and functional hydrogels have demonstrated their potential as platform technologies for atmospheric water (i.e., supersaturated fog and unsaturated water) harvesting due to their cheap price, zero second energy requirement, high water capture capacity, and easy installation and operation compared with traditional water harvesting methods, such as long-distance water transportation, seawater desalination, and electrical dew collection devices in rural areas or individual-scale emergent usage. In this contribution, we highlight recent developments in functional materials for "passive" atmospheric water harvesting application, focusing on the structure-property relationship (SPR) to illustrate the transport mechanism of water capture and release. We also discuss technical challenges in the practical applications of the water harvesting materials, including low adaptability in a harsh environment, low capacity under low humidity, self-desorption, and insufficient solar-thermal conversion. Finally, we provide insightful perspectives on the design and fabrication of atmospheric water harvesting materials.

High-yield and scalable water harvesting of honeycomb hygroscopic polymer driven by natural sunlight

Many materials have been tailored for sorption-based solar-thermal-driven atmospheric water harvesting (AWH), but AWH devices are still inefficient and unscalable. To close the large gap between materials research and practical application, a hydrogel-based composite sorbent (PCLG) with high adsorption capacity per unit volume has been developed with an optimized honeycomb structure, which has potential applications in global water harvesting. The PCLG sorbent achieves 1.8 g/cm 3 water harvested under 30°C and 30% relative humidity (RH). The optimized honeycomb structure enables 50% water absorption improvement due to better heat and mass transfer performance. In outdoor experiments, our water harvester realizes 2.9 L/m 2 /day of water collected per cycle under natural sunlight. Based on PCLG properties and worldwide weather data, our device can yield up to 6 L/m 2 /day of water. The high adsorption/desorption hydrogel sorbent and scalable atmospheric water harvester offer a solution for efficiently extracting water from the air to relieve the thirsty world. • PCLG is a high-efficiency sorbent suitable for AWH in a wide humidity range • Per unit volume adsorption capacity is proposed as an important indicator for AWH • An integrated device with honeycomb PCLG is designed to improve AWH efficiency • Water production of PCLG-based AWH is predicted to validate its global potential There remains a large gap between atmospheric water harvesting materials development and their practical application. Here, Wang et al. report a hydrogel-based composite sorbent with high adsorption capacity per unit volume, demonstrated to harvest 2.9 L/m 2 /day outdoors under natural sunlight as part of an integrated device with a honeycomb structure.

Linker Functionalization Strategy for Water Adsorption in Metal-Organic Frameworks.

Water adsorption in metal–organic frameworks has gained a lot of scientific attention recently due to the potential to be used in adsorption-based water capture. Functionalization of their organic linkers can tune water adsorption properties by increasing the hydrophilicity, thus altering the shape of the water adsorption isotherms and the overall water uptake. In this work, a large set of functional groups is screened for their interaction with water using ab initio calculations. The functional groups with the highest water affinities form two hydrogen bonds with the water molecule, acting as H-bond donor and H-bond acceptor simultaneously. Notably, the highest binding energy was calculated to be −12.7 Kcal/mol for the -OSO3H group at the RI-MP2/def2-TZVPP-level of theory, which is three times larger than the reference value. Subsequently, the effect of the functionalization strategy on the water uptake is examined on a selected set of functionalized MOF-74-III by performing Monte Carlo simulations. It was found that the specific groups can increase the hydrophilicity of the MOF and enhance the water uptake with respect to the parent MOF-74-III for relative humidity (RH) values up to 30%. The saturation water uptake exceeded 800 cm3/cm3 for all candidates, classifying them among the top performing materials for water harvesting.

Special Wettability Materials Inspired by Multiorganisms for Fog Collection

AbstractAt present, the shortage of fresh water resources has become a serious problem that human beings have to face. Especially in some arid areas, water shortage has threatened human existence. The discovery that some organisms can survive in extremely arid areas by trapping water in fog has inspired research into bionic water harvesting materials. The emergence of such biomimetic materials offers a potential strategy for tackling the freshwater crisis. This paper reviews the mechanism of some organisms’ water collecting function and special liquid handling ability and the research progress of biomimetic fog‐collecting materials. In addition, the bionic water collecting materials which creatively combine the advantages of various organisms are introduced in detail. It is hoped that these innovative combinations can bring inspiration to the design of fog collecting materials in the future. Finally, the research and development prospects of materials inspired by multiorganisms are prospected.

Machine Learning-Assisted Computational Screening of Metal-Organic Frameworks for Atmospheric Water Harvesting.

Atmospheric water harvesting by strong adsorbents is a feasible method of solving the shortage of water resources, especially for arid regions. In this study, a machine learning (ML)-assisted high-throughput computational screening is employed to calculate the capture of H2O from N2 and O2 for 6013 computation-ready, experimental metal-organic frameworks (CoRE-MOFs) and 137,953 hypothetical MOFs (hMOFs). Through the univariate analysis of MOF structure-performance relationships, Qst is shown to be a key descriptor. Moreover, three ML algorithms (random forest, gradient boosted regression trees, and neighbor component analysis (NCA)) are applied to hunt for the complicated interrelation between six descriptors and performance. After the optimizing strategy of grid search and five-fold cross-validation is performed, three ML can effectively build the predictive model for CoRE-MOFs, and the accuracy R2 of NCA can reach 0.97. In addition, based on the relative importance of the descriptors by ML, it can be quantitatively concluded that the Qst is dominant in governing the capture of H2O. Besides, the NCA model trained by 6013 CoRE-MOFs can predict the selectivity of hMOFs with a R2 of 0.86, which is more universal than other models. Finally, 10 CoRE-MOFs and 10 hMOFs with high performance are identified. The computational screening and prediction of ML could provide guidance and inspiration for the development of materials for water harvesting in the atmosphere.

Multibioinspired Wettable Patterned Slippery Surface for Efficient Water Harvesting

AbstractIt is highly desirable to endow surfaces with both exceptional droplet nucleation and removal capacities for water harvesting, but which still remains great challenges. Inspired by the water collection features of desert beetles and Nepenthes pitcher, this paper presents a facile and simple strategy to fabricate a wettable patterned slippery surface (WPSS). Different from desert beetles‐inspired water harvesting materials which the (super) hydrophilic bumps are constructed on a (super) hydrophobic background, the patterned hydrophilic CuO bumps in this study are surrounded by the silicone oil layer. Owing to the patterned hydrophilic bumps and slippery interface, as well as the flexibility in manipulating the relative ratio between them, the innovated WPSS is capable of rapidly nucleating and removing water droplets. It outperforms conventional liquid‐repellent surfaces in water harvesting performance.

One-Step Preparation of Hydrophobic Surfaces Containing Hydrophilic Groups for Efficient Water Harvesting.

Multifunctional surfaces that are favorable for both droplet nucleation and removal are critical for water-harvesting applications, but there still remain great challenges. Herein, we proposed a facile strategy to construct hydrophobic surfaces containing moderate hydrophilic groups to achieve both exceptional droplet nucleation and removal. Different from natural desert beetle-inspired water-harvesting materials, these surfaces utilize limited hydrophilic domains to condense fog, and transport of formed tiny droplets relies on a hydrophobic background. The total surface area of the presented hydrophobic fabric contains hydrophilic groups, and the areas for trapping fog have increased. This feature is optimized to enhance the droplet nucleation density, and the surface still has excellent liquid repellency, resulting in maximum water collection efficiency of the prepared surface reaching up to 3.145 g·cm-2·h-1, much higher than the most reported water-harvesting materials. Due to its high efficiency and scalability, we believe that the proposed strategy to construct hydrophobic surfaces containing hydrophilic groups has great practical value.

Doping of inosine in guanosine dihydrate and its effects on reversible water harvesting property

Guanosine (GR) dihydrate and inosine (IR) dihydrate have similar crystal structure, water molecules are almost at the same locations in them. GR dihydrate has the reversible dehydration/hydration property and is a good candidate for materials harvesting water from atmosphere. IR dihydrate is not stable and can be easily transformed to anhydrous IR α form. In this work, doping of IR in GR dihydrate in all the range was realized for the first time by using a solution method. The successful preparation of doped dihydrate of IR and GR by the solution method was attributed to the similar molecular conformations of IR and GR in solution. The doped dihydrates could maintain the reversible dehydration/hydration property similar to pure GR dihydrate even the ratio of IR was up to 71.1 ± 1.2 mol% under a mild drying treatment with freeze-dry. A pure amorphous GR was prepared by ball milling, and it showed a similar dehydration/hydration property to GR dihydrate with a lower dehydration temperature (about 84 °C). The implementation of doping IR in GR dihydrate would shed light on the design and fabrication of functional doped organic crystals. And study on the structural insights and the dehydration/hydration processes of the doped dihydrates and the pure amorphous GR would shed light on the design and fabrication of novel hydrogen-bonded organic frameworks (HOFs) materials for water harvesting.

Learning from plants: a new framework to approach water-harvesting design concepts

PurposeThis paper's main objective is to focus on the water-harvesting ability of plants and try to implement a solution-based method to outline a plant-inspired design framework.Design/methodology/approachThe current paper aims to provide a step-by-step approach to the biological-inspired design by looking deeply at plants' mechanisms and features to harvest water and conduct a method to learn them in an organized way.FindingsIn addition to the proposed framework, the fundamental water-harvesting principles of plants including increasing condensation, reducing transpiration and facilitating transportation have been extracted by investigating several adaptable plants. The relevant factors related to each of these three principles are introduced and can potentially ease the process of bio-inspiration as it contributes to the findability and understandability of a particular biologic strategy. As a result, this framework can be used to the formation of novel designs in different disciplines. In this process, the development of an architectural design concept is presented as an example.Originality/valueThe current global issue about the shortage of water leads researchers to learn adaptability from nature and increase the demands of using bio-inspired strategies. The novelty of this study is to introduce a water-harvesting design path, which has been presented using a four-step-plant-to-design process. Learning from plants' water-harvesting strategies will contribute to efficiency in different disciplines. The findings of this study have important implications for developing bio-inspired water-harvesting materials and systems. Moreover, the findings add substantially to the understanding of water-harvesting architecture and play an important role in bridging the gap between theory and practice.