An Interfacial Solar-Driven Atmospheric Water Generator Based on a Liquid Sorbent with Simultaneous Adsorption-Desorption

An Atmospheric Water-Harvester with Ultrahigh Uptake-Release Efficiency at Low Humidity

Atmospheric water harvesting is a practical strategy that is achieved by removing materials from air moisture to relieve global water scarcity. Here we design a water-harvester (i.e., MOF-303/thiolated polymer composite (MTC)) by using a metal-organic framework (MOF-303) and thiolated chitosan (TC) skeleton. Intermolecular hydrogen bonding between TC and MOF-303 facilitates porous structures with enlarged air-polymer interfaces for long cycling life and high capacity at low relative humidity. Benefiting from synergetic effects on porosity and anchorage for accelerating the uptake-release of moisture, MTC exhibits a rapid water uptake capacity of 0.135 g/g in 60 min under 12.5 RH% and ultrafast water desorption kinetics of 0.003 g/g/min at 8.5 RH%, which is superior to the as-reported MOF-303 based adsorbents. At low heat (∼40 °C), the water desorption and collection rate, respectively, are 0.0195 and 0.0168 g/g/min within 210 min, showing ultrahigh harvesting efficiency. These results highlight the enormous potential as promising materials for solving the world's water scarcity crisis. This study offers an insight into the design of AWH materials, which can be extended into applications in some realms, e.g., freshwater development for industry in arid areas, water engineering-related devices and systems, etc.

Entangled Mesh Hydrogels with Macroporous Topologies via Cryogelation for Rapid Atmospheric Water Harvesting

Sorption-based atmospheric water harvesting (SAWH) is a promising technology to alleviate freshwater scarcity. Recently, hygroscopic salt-hydrogel composites (HSHCs) have emerged as attractive candidates with their high water uptake, versatile designability, and scale-up fabrication. However, achieving high-performance SAWH applications for HSHCs has been challenging because of their sluggish kinetics, attributed to their limited mass transport properties. Herein, a universal network engineering of hydrogels using a cryogelation method is presented, significantly improving the SAWH kinetics of HSHCs. As a result of the entangled mesh confinements formed during cryogelation, a stable macroporous topology is attained and maintained within the obtained entangled-mesh hydrogels (EMHs), leading to significantly enhanced mass transport properties compared to conventional dense hydrogels (CDHs). With it, corresponding hygroscopic EMHs (HEMHs) simultaneously exhibit faster moisture sorption and solar-driven water desorption. Consequently, a rapid-cycling HEMHs-based harvester delivers a practical freshwater production of 2.85 Lwater kgsorbents -1 day-1 via continuous eight sorption/desorption cycles, outperforming other state-of-the-art hydrogel-based sorbents. Significantly, the generalizability of this strategy is validated by extending it to other hydrogels used in HSHCs. Overall, this work offers a new approach to efficiently address long-standing challenges of sluggish kinetics in current HSHCs, promoting them toward the next-generation SAWH applications.

Macroporous, Highly Hygroscopic, and Leakage-Free Composites for Efficient Atmospheric Water Harvesting

Hygroscopic composites based on hygroscopic salts and hydrogels are promising for atmospheric water harvesting (AWH), but their relatively low water production and possible salt leakage hinder real applications. Here, we report highly hygroscopic and leakage-free composites from loading LiCl into emulsion-templated sodium alginate and poly(vinyl alcohol) hydrogels with macroporous structures and interpenetrating polymer networks. The resulting composites exhibited an enhanced moisture uptake (up to 3.4 g g-1) and leakage-free behavior even at an extremely high relative humidity (RH) of 90%. Moreover, the composites showed accelerated adsorption, with high adsorption (0.803 g g-1 water at 25 °C and 90% RH within 1 h) and desorption due to the emulsion-templated, highly interconnected macropores. The hygroscopic composites obtained 1.12 g g-1 water per adsorption-desorption collection cycle and showed high reusability, without obvious deterioration in adsorption, desorption, and collection after 10 cycles. With the presence of carbon nanotubes, solar-driven AWH could be realized, without the requirement of additional energy. The highly hygroscopic and leakage-free composites with enhanced and accelerated adsorption and desorption are excellent candidates for efficient AWH.

Progress and perspectives of sorption-based atmospheric water harvesting for sustainable water generation: Materials, devices, and systems

Establishing alternative methods for freshwater production is imperative to effectively alleviate global water scarcity, particularly in land-locked arid regions. In this context, extracting water from the ubiquitous atmospheric moisture is an ingenious strategy for decentralized freshwater production. Sorption-based atmospheric water harvesting (SAWH) shows strong potential for supplying liquid water in a portable and sustainable way even in desert environments. Herein, the latest progress in SAWH technology in terms of materials, devices, and systems is reviewed. Recent advances in sorbent materials with improved water uptake capacity and accelerated sorption-desorption kinetics, including physical sorbents, polymeric hydrogels, composite sorbents, and ionic solutions, are discussed. The thermal designs of SAWH devices for improving energy utilization efficiency, heat transfer, and mass transport are evaluated, and the development of representative SAWH prototypes is clarified in a chronological order. Thereafter, state-of-the-art operation patterns of SAWH systems, incorporating intermittent, daytime continuous and 24-hour continuous patterns, are examined. Furthermore, current challenges and future research goals of this cutting-edge field are outlined. This review highlights the irreplaceable role of heat and mass transfer enhancement and facile structural improvement for constructing high-yield water harvesters.

Hierarchical Engineering of Sorption-Based Atmospheric Water Harvesters

Harvesting water from air in sorption-based devices is a promising solution to decentralized water production, aiming for providing potable water anywhere, anytime. This technology involves a series of coupled processes occurring at distinct length scales, ranging from nanometer to meter and even larger, including water sorption/desorption at the nanoscale, condensation at the mesoscale, device development at the macroscale and water scarcity assessment at the global scale. Comprehensive understanding and bespoke designs at every scale are thus needed to improve the water-harvesting performance. For this purpose, a brief introduction of the global water crisis and its key characteristics is provided to clarify the impact potential and design criteria of water harvesters. Next the latest molecular-level optimizations of sorbents for efficient moisture capture and release are discussed. Then, novel microstructuring of surfaces to enhance dropwise condensation, which is favorable for atmospheric water generation, is shown. After that, system-level optimizations of sorbent-assisted water harvesters to achieve high-yield, energy-efficient, and low-cost water harvesting are highlighted. Finally, future directions toward practical sorption-based atmospheric water harvesting are outlined.

Advanced Material Design and Engineering for Water-Based Evaporative Cooling

Water-based evaporative cooling is emerging as a promising technology to provide sustainable and low-cost cold to alleviate the rising global cooling demand. Given the significant and fast progress made in recent years, this review aims to provide a timely overview on the state-of-the-art material design and engineering in water-based evaporative cooling. The fundamental mechanisms and major components of three water-based evaporative cooling processes are introduced, including direct evaporative cooling, cyclic sorption-driven liquid water evaporative cooling (CSD-LWEC), and atmospheric water harvesting-based evaporative cooling (AWH-EC). The distinctive requirements on the sorbent materials in CSD-LWEC and AWH-EC are highlighted, which helps synthesize the literature information on the advanced material design and engineering for the purpose of improving cooling performance. The challenges and future outlooks on further improving the water-based evaporative cooling performance are also provided.

Biopolymers for Hygroscopic Material Development

The effective management of atmospheric water will create huge value for mankind. Diversified and sustainable biopolymers that are derived from organisms provide rich building blocks for various hygroscopic materials. Here, a comprehensive review of recent advances in developing biopolymers for hygroscopic materials is provided. It is begun with a brief introduction of species diversity and the processes of obtaining various biopolymer materials from organisms. The fabrication of hygroscopic materials is then illustrated, with a specific focus on the use of biopolymer-derived materials as substrates to produce composites and the use of biopolymers as building blocks to fabricate composite gels. Next, the representative applications of biopolymer-derived hygroscopic materials for dehumidification, atmospheric water harvesting, and power generation are systematically presented. An outlook on future challenges and key issues worthy of attention are finally provided.

Metal-Organic Frameworks for Water Harvesting and Concurrent Carbon Capture: A Review for Hygroscopic Materials

As water scarcity becomes a pending global issue, hygroscopic materials prove a significant solution. Thus, there is a good cause following the structure-performance relationship to review the recent development of hygroscopic materials and provide inspirational insight into creative materials. Herein, traditional hygroscopic materials, crystalline frameworks, polymers, and composite materials are reviewed. The similarity in working conditions of water harvesting and carbon capture makes simultaneously addressing water shortages and reduction of greenhouse effects possible. Concurrent water harvesting and carbon capture is likely to become a future challenge. Therefore, an emphasis is laid on metal-organic frameworks (MOFs) for their excellent performance in water and CO2 adsorption, and representative role of micro- and mesoporous materials. Herein, the water adsorption mechanisms of MOFs are summarized, followed by a review of MOF's water stability, with a highlight on the emerging machine learning (ML) technique to predict MOF water stability and water uptake. Recent advances in the mechanistic elaboration of moisture's effects on CO2 adsorption are reviewed. This review summarizes recent advances in water-harvesting porous materials with special attention on MOFs and expects to direct researchers' attention into the topic of concurrent water harvesting and carbon capture as a future challenge.

Advanced Cooling Textiles: Mechanisms, Applications, and Perspectives

High-temperature environments pose significant risks to human health and safety. The body's natural ability to regulate temperature becomes overwhelmed under extreme heat, leading to heat stroke, dehydration, and even death. Therefore, the development of effective personal thermal-moisture management systems is crucial for maintaining human well-being. In recent years, significant advancements have been witnessed in the field of textile-based cooling systems, which utilize innovative materials and strategies to achieve effective cooling under different environments. This review aims to provide an overview of the current progress in textile-based personal cooling systems, mainly focusing on the classification, mechanisms, and fabrication techniques. Furthermore, the challenges and potential application scenarios are highlighted, providing valuable insights for further advancements and the eventual industrialization of personal cooling textiles.

Research Progress on Hygroscopic Agents for Atmospheric Water Harvesting Systems

Adsorptive atmospheric water harvesting systems (AWHs) represent an innovative approach to collecting freshwater resources from the atmosphere, with a hygroscopic agent at their core. This method has garnered significant attention due to its broad applicability, strong recycling capacity, and sustainability. It is being positioned as a key technology to address global freshwater scarcity. The core agent's hygroscopic properties play a crucial role in determining the performance of the AWHs. This article provides a comprehensive review of the latest advancements in hygroscopic agents, including their adsorption mechanisms and classifications. This study of hygroscopic agents analyzes the performance and characteristics of relevant porous material composite polymer composites and plant composites. It also evaluates the design and preparation of these materials. Aiming at the problems of low moisture adsorption and desorption difficulty of the hygroscopic agent, the factors affecting the water vapor adsorption performance and the method of enhancing the hygroscopic performance of the material are summarized and put forward. For the effect of hygroscopic agents on the volume of water catchment devices, the difference in density before and after hygroscopicity is proposed as part of the evaluation criteria. Moisture absorption per unit volume is added as a performance evaluation criterion to assess the effect of hygroscopic agents on the volume of water collection equipment. The article identifies areas that require further research and development for moisture absorbers, exploring their potential applications in other fields and anticipating the future development direction and opportunities of moisture-absorbing materials. The goal is to promote the early realization of adsorptive atmospheric water harvesting technology for large-scale industrial applications.

A review of the methods of harvesting atmospheric moisture

Moisture is an inherent constituent of air present across the world. The relative humidity varies with the change in temperature and climate specific to a region. In some regions of the world, there may be a relatively inadequate number of grains of moisture in the air in comparison with other regions. These factors widen the scope for the deployment of decentralized technology to capture water. The effectiveness in capturing moisture gains significance in these regions. Among the numerous forms of moisture, fog and dew are studied in depth. Over time, flora and fauna in different ecosystems have adapted to capture moisture as well as repel excesses of it according to their requirements. Therefore, bio-inspired studies and tailored engineering strategies have been incorporated in this review. Since efficient technologies are required at moisture-scarce locations, active moisture harvesting has also been studied. The use of innovative materials along with different energy sources to capture water is elaborated. The effects of climate change and environmental contamination on harvested moisture are therefore assessed. Community participation and economical use of harvested fog or dew influence the sustainability of moisture-capture projects. Therefore, this article also provides an insight into the services of decentralized water-harvesting projects run by diverse organizations and researchers across the globe.

Autonomous Atmospheric Water Harvesting over a Wide RH Range Enabled by Super Hygroscopic Composite Aerogels

Sorption-based atmospheric water harvesting (SAWH) offers a sustainable strategy to address the global freshwater shortage. However, obtaining sorbents with excellent performance over a wide relative humidity (RH) range and devices with fully autonomous water production remains challenging. Herein, magnesium chloride (MgCl2) is innovatively converted into super hygroscopic magnesium complexes(MC), which can effectively solve the problems of salt deliquescence and agglomeration. The MC are then integrated with photothermal aerogels composed of sodium alginate and carbon nanotubes (SA/CNTs) to form composite aerogels, which showed high water uptake over a wide RH range, reaching 5.43 and 0.27 kg kg-1 at 95% and 20% RH, respectively. The hierarchical porous structure enables the as-prepared SA/CNTs/MC to exhibit rapid absorption/desorption kinetics with 12 cycles per day at 70% RH, equivalent to a water yield of 10.0 L kg-1 day-1. To further realize continuous and practical freshwater production, a fully solar-driven autonomous atmospheric water generator is designed and constructed with two SA/CNTs/MC-based absorption layers, which can alternately conduct the water absorption/desorption process without any other energy consumption. The design provides a promising approach to achieving autonomous, high-performance, and scalable SAWH.

Accelerated Water Desorption of Oligomeric Poly(ethylene glycol) by Addition of Poly(propylene glycol) for Energy-Efficient Water Recovery Systems

Adsorbents are used to recover water vapor from the atmosphere in desiccant air conditioning (DAC) and atmospheric water harvesting (AWH) systems. Solid adsorbents have been conventionally used in these systems, though liquid adsorbents are considered to be more effective for energy-efficient fluidic thermosystems because of their low regeneration temperatures (45-70 °C). While most previous studies have focused on improving the adsorption performance, the desorption performance of adsorbents can also be a critical factor in improving the energy efficiency of these systems. Thus, this study aimed to improve the water desorption efficiency, focusing on the liquid adsorbents. We found that mixing hydrophobic molecules into a liquid adsorbent decreases the desorption temperature and increases the water-desorption efficiency. Oligomeric poly(ethylene glycol) (PEG), a common moisture-adsorbing liquid oligomer used in detergents and cosmetics, was selected as the liquid adsorbent. Oligomeric poly(propylene glycol) (PPG), which has a structure analogous to PEG and lower hygroscopicity, was selected as the hydrophobic molecule. Water adsorption and desorption experiments showed that the mixture of PPG with PEG promoted the desorption of water molecules beyond that of PEG, while thermogravimetric differential thermal analysis revealed a decrease in the water desorption temperature with increasing PPG content. The improved desorption efficiency was ascribed to the likely water adsorption equilibrium between PEG and PPG in the blend; water molecules are preferentially desorbed from PPG, which has weaker water-adsorbate interactions. The proposed concept is expected to be incorporated into various hygroscopic liquids to develop energy-efficient liquid adsorbents for DAC and AWH.

Wood-based capillary enhancers for accelerated moisture capture and solar-powered release

The pressing need to address the global water crisis has spurred research efforts toward exploring alternative sources and technologies, and harvesting atmospheric water from the humid air emerges as a promising solution. Liquid desiccants, known for their high absorption capacity, have been widely utilized for moisture capture, but their water yield is mainly restricted by sluggish adsorption and desorption dynamics. To address this limitation, we present a facile strategy to promote the absorption/desorption dynamics of moisture by virtue of capillary transport and enlarged interfaces in a photothermal wood enhancer. These enhancers are fabricated via partial delignification of natural balsa woods followed by low-temperature carbonization to endow them with photothermal properties. The moisture absorption rate shows a notable increase of 103% and 84% under the relative humidity (RH) of 60% and 90%, respectively, within the initial two hours by applying the three enhancers. On the other hand, the desorption efficiency is doubled, reaching 80% in two hours under 60 °C with the enhancers. Moreover, the desorption can be driven by solar energy with an evaporation rate of 1.217 kg·m-2·h-1. This work provides a design strategy combining capillary and interfacial effects to enhance moisture harvesting without altering hygroscopic materials.

Guar Gum-Based Macroporous Hygroscopic Polymer for Efficient Atmospheric Water Harvesting

Solar-driven atmospheric water harvesting technology has the advantage of not being limited by geography and has great potential in solving the freshwater crisis. Here, we first propose a purely natural and degradable superhydrophilic composite macroporous hygroscopic material by applying guar gum (GG) to atmospheric water harvesting. The material consists of GG-cellulose nanofibers (CNFs) as a porous substrate material, limiting the hygroscopic factor lithium chloride (LiCl) in its three-dimensional (3D) network structure, and carbon nanotubes (CNTs) play a photothermal conversion role. The composite material has a high light absorption rate of more than 95%, and the macroporous structure (20-60 μm) allows for rapid adsorption/desorption kinetics. At 35 °C and 90% relative humidity (RH), the moisture absorption capacity is as high as 1.94 g/g. Under 100 mW/cm2 irradiation, the absorbed water is almost completely desorbed within 3 h, and the water harvesting performance is stable in 10 cycles. Moreover, liquid water was successfully collected in an actual outdoor experiment. This work demonstrates the great potential of biomass materials in the field of atmospheric water collection and provides more opportunities for various energy and sustainable applications in the future.

Sorption-Based Atmospheric Water Harvesting: Materials, Components, Systems, and Applications

Freshwater scarcity is a global challenge posing threats to the lives and daily activities of humankind such that two-thirds of the global population currently experience water shortages. Atmospheric water, irrespective of geographical location, is considered as an alternative water source. Sorption-based atmospheric water harvesting (SAWH) has recently emerged as an efficient strategy for decentralized water production. SAWH thus opens up a self-sustaining source of freshwater that can potentially support the global population for various applications. In this review, the state-of-the-art of SAWH, considering its operation principle, thermodynamic analysis, energy assessment, materials, components, different designs, productivity improvement, scale-up, and application for drinking water, is first extensively explored. Thereafter, the practical integration and potential application of SAWH, beyond drinking water, for wide range of utilities in agriculture, fuel/electricity production, thermal management in building services, electronic devices, and textile are comprehensively discussed. The various strategies to reduce human reliance on natural water resources by integrating SAWH into existing technologies, particularly in underdeveloped countries, in order to satisfy the interconnected needs for food, energy, and water are also examined. This study further highlights the urgent need and future research directions to intensify the design and development of hybrid-SAWH systems for sustainability and diverse applications.

Divide and Conquer: A Novel Dual-Layered Hydrogel for Atmospheric Moisture Harvesting

Atmospheric water harvesting (AWH) has been recognized as a next-generation technology to alleviate water shortages in arid areas. However, the current AWH materials suffer from insufficient water adsorption capacity and high-water retention, which hinder the practical application of AWH materials. In this study, we developed a novel dual-layered hydrogel (DLH) composed of a light-to-heat conversion layer (LHL) containing novel polydopamine-manganese nanoparticles (PDA-Mn NPs) and a water adsorption layer (WAL) made of 2-(acryloyloxyethyl) trimethylammonium chloride (AEtMA). The WAL has a strong ability to adsorb water molecules in the air and has a high-water storage capacity, and the PDA-Mn NPs embedded in the LHL have excellent photothermal conversion efficiency, leading to light-induced autonomous water release. As a result, the DLH displays a high-water adsorption capacity of 7.73 g g^-1 under optimal conditions and could near-quantitatively release captured water within 4 h sunlight exposure. Coupled with its low cost, we believed that the DLH will be one of the promising AWH materials for practical applications.

2D Covalent Organic Framework for Water Harvesting with Fast Kinetics and Low Regeneration Temperature

Atmospheric water harvesting represents a promising technique to address water stress. Advanced adsorbents have been rationally designed to achieve high water uptake, yet their water sorption kinetics and regeneration temperature greatly limit water production efficiency. Herein, we demonstrated that 2D covalent organic frameworks (COFs), featuring hydrophobic skeleton, proper hydrophilic site density, and 1D open channels significantly lowered the water diffusion and desorption energy barrier. DHTA-Pa COF showed a high water uptake of 0.48 g/g at 30 % R.H. with a remarkable adsorption rate of 0.72 L/Kg/h (298 K) and a desorption rate of 2.58 L/Kg/h (333 K). Moreover, more than 90 % adsorbed water could be released within 20 min at 313 K. This kinetic performance surpassed the reported porous materials and boosted the efficiency for multiple water extraction cycles. It may shed light on the material design strategy to achieve high daily water production with low-energy input.

Fe-Co controlled super-hygroscopic hydrogels toward efficient atmospheric water harvesting

Extracting atmospheric moisture for freshwater production is an appealing way to mitigate the global water crisis. However, the low moisture sorption capacity and high desorption temperature are the major bottlenecks for efficient atmospheric water harvesting. Herein, we develop a transition metal super-hygroscopic hydrogel by an economical strategy, which is constructed through a facile coordination between metal salts and ethanolamine. When the empty electron orbital of the metal ion is coordinated with the lone electron pair of nitrogen or oxygen atom, the water active sorption site is formed. A single water layer is bonded on the sites by a coordination effect, followed by physical interaction with water to form multi-layer structures. The Fe and Co ions in the hydrogel function as dual sorption sites to capture moisture, which can harvest additional water by the synergistic effect of bimetals. As a result, the bimetal hydrogel contributes to a high water uptake of 5.22 g g^-1 at 95% RH, triggering the desorption process by one solar intensity due to its low desorption temperature (≤50 °C).

Sustainable Hierarchical-Pored PAAS-PNIPAAm Hydrogel with Core-Shell Structure Tailored for Highly Efficient Atmospheric Water Harvesting

As an effective way to obtain freshwater resources, atmospheric water harvesting (AWH) technology has been a wide concern of researchers. Therefore, hydrogels gradually become key materials for atmospheric water harvesters due to their high specific surface area and three-dimensional porous structure. Here, we construct a core-shell hydrogel-based atmospheric water harvesting material consisting of a shell sodium polyacrylate (PAAS) hydrogel with an open pore structure and a core thermosensitive poly N-isopropylacrylamide (PNIPAAm) hydrogel with a large pore size. Theoretically, the mutual synergistic hygroscopic effect between the core layer and the shell layer accelerates the capture, transport, and storage of moisture to achieve continuous and high-capacity moisture adsorption. Simultaneously, the integration of polydopamine (PDA) with the hydrogel realizes solar-driven photothermal evaporation. Therefore, the prepared core-shell hydrogel material possesses great advantages in water adsorption capacity and water desorption capacity with an adsorption of 2.76 g g^-1 (90% RH) and a desorption of 1.42 kg m^-2 h^-1. Additionally, the core-shell structure hydrogel collects 1.31 g g^-1 day^-1 of fresh water in outdoor experiments, which verifies that this core-shell hydrogel with integrated photothermal properties can capture moisture in a wide range of humidity without any external energy consumption, can further sustainably obtain fresh water in remote water-shortage areas.

Simultaneous atmospheric water production and 24-hour power generation enabled by moisture-induced energy harvesting

Water and electricity scarcity are two global challenges, especially in arid and remote areas. Harnessing ubiquitous moisture and sunlight for water and power generation is a sustainable route to address these challenges. Herein, we report a moisture-induced energy harvesting strategy to realize efficient sorption-based atmospheric water harvesting (SAWH) and 24-hour thermoelectric power generation (TEPG) by synergistically utilizing moisture-induced sorption/desorption heats of SAWH, solar energy in the daytime and radiative cooling in the nighttime. Notably, the synergistic effects significantly improve all-day thermoelectric power density (~346%) and accelerate atmospheric water harvesting compared with conventional designs. We further demonstrate moisture-induced energy harvesting for a hybrid SAWH-TEPG device, exhibiting high water production of 750 g m-2, together with impressive thermoelectric power density up to 685 mW m-2 in the daytime and 21 mW m-2 in the nighttime. Our work provides a promising approach to realizing sustainable water production and power generation at anytime and anywhere.

A Wave-Driven Piezoelectrical Film for Interfacial Steam Generation: Beyond the Limitation of Hydrogel

Solar interfacial vapor generation based on low evaporation energy requirements is an effective technology to speed up water purification under natural sunlight, offering great potential to alleviate the current global water crisis. The external electric field and hydrogel are two independent methods enabling low-energy water evaporation. However, the complicated external equipment for generating an electric field and the restricted activation area of hydrogels significantly limit their practical application in steam generation. Thus, a piezoelectric fiber membrane is embedded into a highly hydratable light-absorbing poly(vinyl alcohol) (PVA) hydrogel for synergistic water activation. The integrated evaporator is capable of continuously converting the wave energy reserved in the ocean into electrical energy, activating the water in the hydrogel. It is found that the activation effect leads to an improvement of over 23% compared to a non-piezoelectric hydrogel evaporator. This work provides an evaporation prototype based on the synergistic water activation of wave-triggered electricity and highly hydratable hydrogel.

Exceptional water production yield enabled by batch-processed portable water harvester in semi-arid climate

Sorption-based atmospheric water harvesting has the potential to realize water production anytime, anywhere, but reaching a hundred-gram high water yield in semi-arid climates is still challenging, although state-of-the-art sorbents have been used. Here, we report a portable and modularized water harvester with scalable, low-cost, and lightweight LiCl-based hygroscopic composite (Li-SHC) sorbents. Li-SHC achieves water uptake capacity of 1.18, 1.79, and 2.93 g g−1 at 15%, 30%, and 60% RH, respectively. Importantly, considering the large mismatch between water capture and release rates, a rationally designed batch processing mode is proposed to pursue maximum water yield in a single diurnal cycle. Together with the advanced thermal design, the water harvester shows an exceptional water yield of 311.69 g day−1 and 1.09 g gsorbent−1 day−1 in the semi-arid climate with the extremely low RH of ~15%, demonstrating the adaptability and possibility of achieving large-scale and reliable water production in real scenarios.

High-yield solar-driven atmospheric water harvesting of metal-organic-framework-derived nanoporous carbon with fast-diffusion water channels

Solar-driven, sorption-based atmospheric water harvesting (AWH) offers a cost-effective solution to freshwater scarcity in arid areas. Creating AWH devices capable of performing multiple adsorption-desorption cycles per day is crucial for increasing water production rates matching human water requirements. However, achieving rapid-cycling AWH in passive harvesters has been challenging due to sorbents' slow water adsorption-desorption dynamics. Here we report an MOF-derived nanoporous carbon, a sorbent endowed with fast sorption kinetics and excellent photothermal properties, for high-yield AWH. The optimized structure (40% adsorption sites and ~1.0 nm pore size) has superior sorption kinetics due to the minimized diffusion resistance. Moreover, the carbonaceous sorbent exhibits fast desorption kinetics enabled by efficient solar-thermal heating and high thermal conductivity. A rapid-cycling water harvester based on nanoporous carbon derived from metal-organic frameworks can produce 0.18 L kg_carbon^-1 h^-1 of water at 30% relative humidity under one-sun illumination. The proposed design strategy is helpful to develop high-yield, solar-driven AWH for advanced freshwater-generation systems.

Super-Hygroscopic Calcium Chloride/Graphene Oxide/Poly(N-isopropylacrylamide) Gels for Spontaneous Harvesting of Atmospheric Water and Solar-Driven Water Release

Although atmospheric water harvesting is a promising approach for extracting clean water in water deficient areas, most atmospheric water collectors require additional energy for releasing the water absorbed. It is still challenging to improve both moisture absorption capacity and desorption efficiency of moisture water collectors. Inspired by clean solar energy and the large humidity difference between day and night, super-hygroscopic calcium chloride (CaCl2)/graphene oxide (GO)/poly(N-isopropylacrylamide) (PNIPAM) gels are designed for spontaneous collection of atmospheric water in a wide range of relative humidity (RH) followed by solar-driven release of the water absorbed. An optimal CaCl2/GO/PNIPAM hygroscopic gel possesses a hierarchical porous structure with directional water transport channels, facilitating water capture and release, thus exhibiting a high moisture absorption capacity of up to 3.6 g g-1 at an RH of 90%. Driven by simulated sunlight, the solar-thermal energy conversion effect of the GO component triggers a unique hydrophilic-hydrophobic conformational transition and shrinkage of the PNIPAM for efficient release of the water absorbed. The integration of the spontaneous harvesting of atmospheric water and the solar-driven water release makes the super-hygroscopic gels promising for efficiently utilizing atmospheric water for special applications where water is desperately necessary but unavailable.

Hierarchical Natural Pollen Cell-Derived Composite Sorbents for Efficient Atmospheric Water Harvesting

Freshwater scarcity is a critical challenge threatening human survival especially due to poverty and arid and off-grid regions. Sorption-based atmospheric water harvesting (AWH) has emerged as a promising strategy for clean water production. However, most of the high-capacity sorbents are limited by the poor sorption/desorption kinetics and uncontrollable liquid leakage problem. Inspired by the plant transpiration process, we develop an environmentally friendly LiCl@pollen cell-polypyrrole (LiCl@PC-PPy) composite sorbent by confining the LiCl hygroscopic agent in the cages of the PC-PPy. The composite sorbent exhibits much improved sorption/desorption kinetics owing to the hydrophilicity of the hierarchical porous structure of the pollen cells, which provides abundant water sorption active sites and diffusion pathways and forms a concave meniscus on cell skeletons to maximize the thermal utilization efficiency. Moreover, the big cavities of the PC-PPy cages can serve as a water reservoir to reduce liquid leakage. As a result, the sorbent can capture atmospheric water to 85% of its own weight under 60% relative humidity (RH) within 2 h and rapidly release the water within 1 h under weak light irradiation of 0.8 sun. As a proof-of-concept demonstration, the fabricated AWH device can absorb 1.55 gwater/gsorbent at night and collect 1.53 gwater/gsorbent of water in 1-day outdoor operation, and the collected water can meet the drinking water standards defined by the World Health Organization (WHO) and Environmental Protection Agency (EPA).

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.

Scalable super hygroscopic polymer films for sustainable moisture harvesting in arid environments

Extracting ubiquitous atmospheric water is a sustainable strategy to enable decentralized access to safely managed water but remains challenging due to its limited daily water output at low relative humidity (≤30% RH). Here, we report super hygroscopic polymer films (SHPFs) composed of renewable biomasses and hygroscopic salt, exhibiting high water uptake of 0.64–0.96 g g⁻¹ at 15–30% RH. Konjac glucomannan facilitates the highly porous structures with enlarged air-polymer interfaces for active moisture capture and water vapor transport. Thermoresponsive hydroxypropyl cellulose enables phase transition at a low temperature to assist the release of collected water via hydrophobic interactions. With rapid sorption-desorption kinetics, SHPFs operate 14–24 cycles per day in arid environments, equivalent to a water yield of 5.8–13.3 L kg⁻¹. Synthesized via a simple casting method using sustainable raw materials, SHPFs highlight the potential for low-cost and scalable atmospheric water harvesting technology to mitigate the global water crisis.

Extracting atmospheric water is a sustainable strategy to enable decentralized access to safely managed water but remains impractical due to its limited daily water output at low relative humidity. Here, the authors demonstrate a hygroscopic polymer composed of renewable biomass which allows high water uptake at low relative humidity

A self-floating and integrated bionic mushroom for highly efficient solar steam generation

Solar desalination is considered as a promising approach to solve the shortage of fresh water resources. In this work, inspired by the transpiration of trees, a self-floating and integrated bionic mushroom solar steam generator (BMSSG) is proposed for highly efficient water evaporation. A wooden strip is used to mimic the stipe of the mushroom for water transportation, meanwhile polyvinyl alcohol (PVA) modified graphene aerogels (GA) is used to imitate the pileus of the mushroom for photothermal conversion. After optimizing compositions of the aerogel and sizes of the wooden strip, a high evaporation rate of 1.67 kg m^-2h^-1 is obtained, outcompeting most of other wood-based evaporators. Compared to traditional interfacial evaporation devices, BMSSG is an integrated structure without a thermal insulation layer and an absorbent wick, which not only increases the compactness that is good for stability and reliability, but also reduces the manufacturing cost. Moreover, the BMSSG can self-float on the water like a roly-poly. These advantages indicate that BMSSG will play a significant role in seawater desalination. The feasibility as well as stability and recyclability of the BMSSG for seawater desalination are demonstrated. This bioinspired design provides a low-cost and scalable SSG, which will have a profound impact in future practical applications.

A Nanostructured Moisture-Absorbing Gel for Fast and Large-Scale Passive Dehumidification

Dehumidification is significant for environmental sustainability and human health. Traditional dehumidification methods involve significant energy consumption and have negative impact on the environment. The core challenge is to expose hygroscopic surfaces to the air, and appropriately store the captured water and avoid surface inactivation. Here, a nanostructured moisture-absorbing gel (N-MAG) for passive dehumidification, which consists of a hydrophilic nanocellulose network functionalized by hygroscopic lithium chloride, is reported. The interconnected nanocellulose can transfer the captured water to the internal space of the bulky N-MAG, eliminating water accumulation near the surfaces and hence enabling high-rate moisture absorption. The N-MAG can reduce the relative humidity from 96.7% to 28.7% in 6 h, even if the space is over 2 × 10⁴ times of its own volume. The condensed water can be completely confined in the N-MAG, overcoming the problem of environmental pollution. This research brings a new perspective for sustainable humidity management without energy consumption and with positive environmental footprint.

Immobilization of Lewis Basic Nitrogen Sites into a Chemically Stable Metal-Organic Framework for Benchmark Water-Sorption-Driven Heat Allocations

Developing efficient and stable water adsorbents for adsorption-driven heat transfer technology still remains a challenge due to the lack of efficient strategies to enhance low-pressure water uptakes. The authors herein demonstrate that the immobilization of Lewis basic nitrogen sites into metal-organic frameworks (MOFs) can improve water uptake and target benchmark coefficient of performances (COPs) for cooling and heating. They present the water sorption properties of a chemically stable MOF (termed as Zr-adip), designed by incorporating hydrophilic nitrogen sites into the adsorbent MIP-200. Zr-adip exhibits S-shaped sorption isotherms with an extremely high water uptake of 0.43 g g-1  at 303 K and P/P0  = 0.25, higher than MIP-200 (0.39 g g-1 ), KMF-1 (0.39 g g-1 ) and MOF-303 (0.38 g g-1 ). Theoretical calculations reveal that the incorporated N sites can serve as secondary adsorption sites to moderately interact with water, providing more binding sites to strengthen the water binding affinity. Zr-adip achieves exceptionally high COPs of 0.79 (cooling) and 1.75 (heating) with a low driving temperature of 70 °C, outperforming MIP-200 (0.78 and 1.53) and KMF-1 (0.75 and 1.74). Combined with its ultrahigh stability, excellent cycling performance, and easy regeneration, Zr-adip represents one of the best water adsorbents for adsorption-driven cooling and heating.

Towards sustainable saline agriculture: Interfacial solar evaporation for simultaneous seawater desalination and saline soil remediation

Interfacial solar steam generation is an efficient way to produce freshwater from saline water. This technology was further harnessed here for simultaneous saline soil remediation and enhanced agricultural sustainability. An interfacial solar evaporation and planting system was designed that uses treated seawater for saline soil washing and agricultural irrigation. In outdoor experiments the evaporator realized high freshwater production (10.95 kg m^-2 day^-1) with a soil washing efficiency 3 times greater than traditional distillation. Post treatment plant assays showed that initially highly saline soils could be restored to functional agricultural soils with germination rates of 65% after soil washing, where solar evaporation could continuously provide irrigation water for plant growth. This system is fully automated and uses only solar energy and seawater for saline soil remediation and irrigation. The development of this system provides a potentially useful solution to alleviate global problems associated with water scarcity, soil salinization, and desertification.

Polyzwitterionic Hydrogels for Efficient Atmospheric Water Harvesting

Atmospheric water harvesting (AWH) is regarded as one of the promising strategies for freshwater production desirable to provide sustainable water for landlocked and arid regions. Hygroscopic materials have attracted widespread attention because of their water harvesting performance. However, the introduction of many inorganic salts often leads to aggregation and leakage issues in practical use. Here, polyzwitterionic hydrogels are developed as an effective AWH material platform. Via anti-polyelectrolyte effects, the hygroscopic salt coordinated with polymer chains could capture moisture and enhance the swelling property, leading to a strong moisture sorption capacity. The hydrogel shows superior AWH performance (0.62 g g^-1 , 120 minutes for equilibrium at 30 % relative humidity) and produces 5.87 L kg^-1 freshwater per day. It is anticipated that the polyzwitterionic hydrogels with unique salt-responsive properties could provide new insights into the design and synthesis of next-generation AWH materials.

Highly Transparent and Self-Healable Solar Thermal Anti-/Deicing Surfaces: When Ultrathin MXene Multilayers Marry a Solid Slippery Self-Cleaning Coating

Solar anti-/deicing can solve icing problems by converting sunlight into heat. One of the biggest problems, which has long been plaguing the design of solar anti-/deicing surfaces, is that photothermal materials are always lightproof and appear black, because of the mutual exclusiveness between generating heat and retaining transparency. Herein, a highly transparent and scalable solar anti-/deicing surface is reported, which enables the coated glass to exhibit high transparency (>77% transmittance at 550 nm) and meanwhile causes a >30 °C surface temperature increase relative to the ambient environment under 1.0 sun illumination. Such a transparent anti-/deicing surface can be fabricated onto a large class of substrates (e.g., glass, ceramics, metals, plastics), by applying a solid omniphobic slippery coating onto layer-by-layer-assembled ultrathin MXene multilayers. Hence, the surface possesses a self-cleaning ability to shed waterborne and oil-based liquids thanks to residue-free slipping motion. Passive anti-icing and active deicing capabilities are, respectively, obtained on the solar thermal surface, which effectively prevents water from freezing and simultaneously melts pre-formed ice and thick frost. The self-cleaning effect enables residue-free removal of unfrozen water and interfacially melted ice/frost to boost the anti-/deicing efficiency. Importantly, the surface is capable of self-healing under illumination to repair physical damage and chemical degradation.

Interfacial Radiation-Absorbing Hydrogel Film for Efficient Thermal Utilization on Solar Evaporator Surfaces

Solar water purification is a promising technology with a strong potential for producing fresh water without effluent discharge. For energy-intensive interfacial vapor generation, energy loss to air via heat radiation and convection occurs commonly but is normally ignored, which severely limits the energy efficiency. Therefore, it is necessary to precisely regulate the interfacial thermal energy for interfacial vapor generation. Here, we developed a hierarchically porous radiation-absorbing hydrogel film (hp-RAH) through an in situ gelation strategy and employed this hp-RAH on various existing solar evaporator surfaces. The hydrogel film efficiently absorbs and reutilizes the thermal radiation energy emitted by the photothermal layer and eradicates thermal convection of the photothermal layer into air. In this way, an evaporation efficiency up to 95% is obtained, and the heat radiation and convection losses are reduced from 6.6% to 0.39% under 1 sun. This strategy demonstrates a promising membrane evaporation prototype based on the evaporation surface thermal utilization.

Atmospheric Hygroscopic Ionogels with Dynamically Stable Cooling Interfaces Enable a Durable Thermoelectric Performance Enhancement

In thermoelectric generator (TEG) systems, heat dissipation from their cold sides is an accessible, low-cost, and effective way to increase the temperature gap for their thermoelectric performance enhancement. Although significant efforts have been dedicated mediated by hygroscopic hydrogel coolers as self-sustained alternatives for effective heat removal, it still remains a challenge for overcoming instabilities in their cooling process. The inevitable mechanical deformation of these conventional hydrogels induced by excessive water desorption may cause a detached cooling interface with the targeted substrates, leading to undesirable cooling failure. Herein, a self-sustained and durable evaporative cooling approach for TEG enabled by atmospheric hygroscopic ionogels (RIGs) with stable interfaces to efficiently improve its thermoelectric performance is proposed. Owing to its superior hygroscopicity, the RIGs can achieve higher heat dissipation for TEG through water evaporation than that of common commercial metal heat sinks. Moreover, its favorable adhesion enables the RIG closely interact with the TEG surface either in static or dynamic conditions for a durable thermoelectric performance enhancement. It is believed that such a self-sustained evaporative cooling strategy based on the RIG will have great implications for the enhancement of TEG's efficiency, demonstrating a great promise in intermittent thermal-energy utilizations.

Global potential for harvesting drinking water from air using solar energy

Access to safely managed drinking water (SMDW) remains a global challenge, and affects 2.2 billion people^1,2. Solar-driven atmospheric water harvesting (AWH) devices with continuous cycling may accelerate progress by enabling decentralized extraction of water from air^3-6, but low specific yields (SY) and low daytime relative humidity (RH) have raised questions about their performance (in litres of water output per day)^7-11. However, to our knowledge, no analysis has mapped the global potential of AWH¹² despite favourable conditions in tropical regions, where two-thirds of people without SMDW live². Here we show that AWH could provide SMDW for a billion people. Our assessment-using Google Earth Engine¹³-introduces a hypothetical 1-metre-square device with a SY profile of 0.2 to 2.5 litres per kilowatt-hour (0.1 to 1.25 litres per kilowatt-hour for a 2-metre-square device) at 30% to 90% RH, respectively. Such a device could meet a target average daily drinking water requirement of 5 litres per day per person¹⁴. We plot the impact potential of existing devices and new sorbent classes, which suggests that these targets could be met with continued technological development, and well within thermodynamic limits. Indeed, these performance targets have been achieved experimentally in demonstrations of sorbent materials^15-17. Our tools can inform design trade-offs for atmospheric water harvesting devices that maximize global impact, alongside ongoing efforts to meet Sustainable Development Goals (SDGs) with existing technologies.

Enhanced adsorption-based atmospheric water harvesting using a photothermal cotton rod for freshwater production in cold climates

Solar energy-powered adsorption-based atmospheric water harvesting (ABAWH) is an emerging technology for freshwater production, especially in water-scarce regions that are remote and landlocked. Numerous water adsorbents have been used in ABAWH devices to convert molecule to liquid water. However, it is still challenging to harvest water from the air in cold winter, owing to the water adsorption of sorbents decreasing significantly at low temperature. Herein, we designed and fabricated an ABAWH device by integrating composited ionic liquids (CILs) with carbon nanotubes (CNTs) photothermal materials on the surface of cotton rod fibers. CILs extract water from the air. CNTs enable light-to-heat conversion and drive the solar evaporation process. Importantly, the cotton rods offer a backbone porous structure to maintain its internal temperature at 20 °C under solar irradiation, and thus promote the water adsorption performance of CILs at low environmental temperature. Freshwater is successfully harvested under environment temperature of 6 °C, 30% RH and solar irradiation intensity of 0.6 kW m⁻². The water yield can achieve 1.49 kg per m² per day in an outdoor environment. We believe that the ABAWH device offers a promising approach to effectively harvest water from the air at low temperature and humidity conditions.

A photothermal cotton rod is designed for the enhanced atmospheric water absorption and solar evaporation for freshwater production in cold climates.

Solar-Powered Sustainable Water Production: State-of-the-Art Technologies for Sunlight-Energy-Water Nexus

Alternative water resources (seawater, brackish water, atmospheric water, sewage, etc.) can be converted into clean freshwater via high-efficiency, energy-saving, and cost-effective methods to cope with the global water crisis. Herein, we provide a comprehensive and systematic overview of various solar-powered technologies for alternative water utilization (i.e., "sunlight-energy-water nexus"), including solar-thermal interface desalination (STID), solar-thermal membrane desalination (STMD), solar-driven electrochemical desalination (SED), and solar-thermal atmospheric water harvesting (ST-AWH). Three strategies have been proposed for improving the evaporation rate of STID systems above the theoretical limit and designing all-weather or all-day operating STID systems by analyzing the energy transfer of the evaporation and condensation processes caused by solar-thermal conversion. This review also introduces the fundamental principles and current research hotspots of two other solar-driven seawater or brackish water desalination technologies (STMD and SED) in detail. In addition, we also cover ST-AWH and other solar-powered technologies in terms of technology design, materials evolution, device assembly, etc. Finally, we summarize the content of this comprehensive review and discuss the challenges and future outlook of different types of solar-powered alternative water utilization technologies.

Performance characterization and application of composite adsorbent LiCl@ACFF for moisture harvesting

Freshwater scarcity is a global threat to modern era of human society. Sorption-based atmospheric water harvesting (AWH) is prospective to provide fresh water for remote water-stressed areas lacking in water and electricity. Adsorbent material plays a vital role in such AWH systems. Here, we report a solid adsorbent synthesized by impregnating hygroscopic salt lithium chloride (LiCl) into solidified activated carbon fiber felt (ACFF modified by silica sol). Composite samples immersed with different mass concentrations of silica sol are prepared and characterized for dynamic water uptake, equilibrium water uptake, textural and thermal properties. AS5Li30 (ACFF + 5 wt% silica gel + 30 wt% LiCl) exhibits an efficient water uptake of 2.1 g/g at 25 °C and 70% relative humidity (RH). The material further demonstrates a heat storage capacity of 5456 kJ/kg. Its low regeneration temperature (< 80 °C) and good cycle stability make it feasible to be used in practical water production applications, driven by solar energy and other low-grade energy. Estimation results show that water harvesting unit can produce 1.41 g_H2O/g_AS5Li30 under 25 °C and 75% RH.

A Roadmap to Sorption-Based Atmospheric Water Harvesting: From Molecular Sorption Mechanism to Sorbent Design and System Optimization

Sorption-based atmospheric water harvesting (SAWH), which uses sorbents to capture water vapor from the air and low-grade energy to produce fresh liquid water, has been recognized as a promising strategy for decentralized water supply in arid areas. This review aims to summarize the latest progress in this field and provide perspectives for the further development of SAWH, focusing on the design of sorbent materials and the optimization of the entire system. We first introduce the water sorption mechanisms on different sorbent materials. Next, we discuss the properties and performances of various sorbents developed for SAWH by categorizing them into specific groups: nanoporous solids, hygroscopic polymers, salt-based composites, and liquid sorbents; for each type of sorbent materials, we have analyzed its advantages and limitations, as well as design strategies. In addition, we discuss the influences of the mass and heat transport of the SAWH system on its overall performance in actual operations, and introduce different types of water harvesters developed for SAWH. In the last section, we outline the challenges in this field from fundamental research and practical application aspects, and describe roadmaps for the future development of this technology.

Metal- and halide-free, solid-state polymeric water vapor sorbents for efficient water-sorption-driven cooling and atmospheric water harvesting

Metal- and halide-free, solid-state water vapor sorbents are highly desirable for water-sorption-based applications, because most of the solid sorbents suffer from low water sorption capacity caused by their rigid porosity, while the liquid sorbents are limited by their fluidity and strong corrosivity, which is caused by the halide ions. Herein, we report a novel type of highly efficient and benign polymeric sorbent, which contains no metal or halide, and has an expandable solid state when wet. A group of sorbents are synthesized by polymerizing and crosslinking the metal-free quaternary ammonium monomers followed by an ion-exchange process to replace chloride anions with benign-anions, including acetate, oxalate, and citrate. They show significantly reduced corrosivity and improved water sorption capacity. Importantly, the water sorption capacity of the acetate paired hydrogel is among the best of the literature reported hygroscopic polymers in their pure form, even though the hydrogel is crosslinked. The hydrogel-based sorbents are further used for water-sorption-driven cooling and atmospheric water harvesting applications, which show improved coefficient of performance (COP) and high freshwater production rate, respectively. The results of this work would inspire more research interest in developing better water sorbents and potentially broaden the application horizon of water-sorption-based processes towards the water-energy nexus.

Self-contained Janus Aerogel with Antifouling and Salt-Rejecting Properties for Stable Solar Evaporation

Janus structural interfacial vaporization by separating the solar absorber from the bulk working fluid has attracted tremendous attention due to its low heat losses and high solar conversion efficiency for desalination, water purification, energy generation, etc. However, a totally separated double-deck structure with a discontinuous interfacial transition and inefficient photothermic materials undermines its long-term use and large-scale practical exploitation. Herein, a low-cost Janus monolithic chitosan aerogel with continuous aligned run-through microchannels has been demonstrated to have a highly efficient photothermic effect on seawater desalination and wastewater purification. The top solar absorber layer enhances broadband light absorption and photothermal conversion efficiency via the multiple internal reflection of incident light in the aligned microchannels. Moreover, the insulating/hydrophilic bottom layer promotes water transportation and heat localization, and simultaneously prevents salt/fouling accumulation. As a result, a long-term solar vaporization rate of ∼1.76 kg m^-2 h^-1 is achieved, corresponding to a light-to-vapor efficiency of ∼91% under 1 sun irradiation. Notably, the large-vessel microchannels throughout the aerogel and favorable swelling property provide sufficient water replenishment and storage for completely isolating self-contained evaporation, illustrating an enhanced and time-extended self-contained solar steam generation. Such a low-cost bilayer aerogel with remarkable cycling stability in various fluids offers potential opportunities for freshwater production in remote rural areas.