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

CO2-Responsive Smart Wood Scaffold for Natural Organic Matter Removal without Secondary Pollution

Ensuring drinking water safety remains a critical challenge, particularly when treating complex water sources, due to secondary pollution caused by active chemical additives. Herein, a novel CO2-responsive smart wood scaffold that leverages non-toxic CO2 activation is developed to achieve highly efficient removal of carcinogenic natural organic matter (NOM) and broad-spectrum microbial disinfection without requiring additional chemical agents. Unlike conventional water purification techniques that face a safety-efficacy trade-off, the multi-stage CO2-responsive wood scaffold offers exceptional tunability in NOM abatement across diverse environmental conditions, including variable water chemistry, NOM composition, high salinity, and real-world water sources. The purified water meets stringent drinking water standards (e.g., UV254 reduction, dissolved organic carbon removal, and bacterial elimination). It is found that the highly efficient NOM adsorption mainly originates from the strong and stable CO2-triggered cation-π interaction between the scaffold surface and aromatic NOM groups, as revealed via high-resolution mass spectrometry and direct intermolecular force measurements. This ecofriendly and contamination-free CO2-responsive strategy provides a transformative approach to overcoming secondary pollution challenges in water purification, offering a scalable and sustainable platform for environmental applications and beyond.

Alterations in vibrational spectra of adsorbed water in MIL-101(Cr) and functionalized MIL-101(Cr) using molecular simulations

The vibrational dynamics of adsorbed water, as reflected in its vibrational density of states (VDOS) spectra, differ significantly from those of bulk water. This study employs molecular simulations to explore these modifications in water confined within MIL-101(Cr) and its sulfonic acid-functionalized derivative, MIL-101-SO3H(Cr). Various water models are tested, with systematic adjustments made to identify the one that best replicates the experimental infrared (IR) spectrum. The optimized model is then used to analyze the vibrational properties of adsorbed water. Normal mode analysis (NMA) decomposes the vibrational signal into the underlying normal modes of water molecules, allowing for a detailed examination of water adsorbed at specific framework sites. At low pressures, water molecules preferentially bind to high-affinity sites, such as the unsaturated Cr centers in MIL-101(Cr) and the sulfonic acid hydroxyl (-OH) groups in MIL-101-SO3H(Cr), exhibiting distinct asymmetric stretching modes compared to bulk water. However, as water uptake increases at higher pressures, the VDOS spectra of adsorbed and bulk water begin to converge, signaling the onset of capillary condensation.

Covalent Organic Frameworks with Regulated Water Adsorption Sites for Efficient Cooling of Electronics

The excessive heat accumulation has been the greatest danger for chips to maintain the computing power. In this paper, a passive thermal management strategy for electronics cooling was developed based on the water vapor desorption process of the covalent organic frameworks (COFs). The precise regulation for the number of carbonyl group and the ratio of hydrophilicity and hydrophobicity within pore channels was achieved by water adsorption sites engineering. In particular, COF-THTA with abundant water adsorption sites exhibited highest water uptake and desorption energy, which facilitate efficient cooling of electronics. In proof-of-concept testing, COF-THTA coating (40×40 mm) provided a temperature drop of 7.5 °C in 25 minutes at a heating power of 937.5 W/m2, and remained stable after 10 intermittent heat cycles. Furthermore, the equivalent enthalpy of COF-THTA coating can reach up to 1136 J/gcoating. In real application scenarios, COF-THTA coating improved the performance of two real computing devices by 26.73 % and 22.61 %, respectively. This strategy based on COFs provides a new thinking for passive thermal management, exhibiting great potential in efficient cooling of electronics.

Active twisting for adaptive droplet collection

Many xeric plant leaves exhibit bending and twisting morphology, which may contribute to their important biological and physical functions adapted to drought and desert conditions. Revealing the relationships between various morphologies and functionalities can inspire device designs for meeting increasingly stringent environmental requirements. Here, demonstrated on the biomimetic bilayer ribbons made of liquid crystal elastomers, we reveal that the stimulus-induced morphological evolution of bending, spiraling, twisting and various coupling states among them can be selectively achieved and precisely tuned by designing the director orientations in liquid crystal elastomer bilayers. The mathematical models and analytical solutions are developed to quantify the morphology selection and phase transition of these liquid crystal elastomer ribbons for material design, as confirmed by experiments. Moreover, we show that, under activation and control of external stimuli, the twisting configuration can be harnessed to effectively collect and guide the transportation of droplets, and enhance the structural stiffness for resisting wind blow and rainfall to achieve the optimal configuration for water collection. Our results reveal the interesting functions correlated with bending, spiraling and twisting morphologies widely present in the natural world, by providing fundamental insights into their shape transformation and controlling factors. This work also demonstrates a potential application with integrating morphogenesis-environment interactions into devices or equipments.

Theoretical investigations of the auxochromic effect on novel thermally activated delayed fluorescence (TADF) anthracene derivatives

Thermally active delayed fluorescence (TADF) of experimentally synthesized anthracene derivatives is studied. The studied compounds are named as 9-cyano-10-diphenylamino-anthracene (Cy-Anth-1), 9-(N-carbazolyl)-10-cyanoanthracene (Cy-Anth-2), 10-(benzofuro[2,3-b] pyridin-6-yl)-N, N-diphenylanthracen-9-amine (Benzo4-Anth-1), 6-(10-(9H-carbazol-9-yl) anthracen-9-yl) benzofuro[2,3-b] pyridine (Benzo4-Anth-2). Chemical characterization and the structure-TADF relationship were determined using the DFT and TD-DFT techniques. The analysis of frontier molecular orbitals and molecular electrostatic potential indicated that the Benzo4-Anth-1 derivative is a good candidate for TADF due to its spatially separated donor and acceptor groups. The energy gap ΔE (S1-T2) of Cy-Anth-1, Cy-Anth-2, Benzo4-Anth-1, and Benzo4-Anth-2 is 0.0057, -0.026, 0.0528, and -0.0635 eV, respectively. While ΔE (T2-T1) for Cy-Anth-1, Cy-Anth-2, Benzo4-Anth-1, and Benzo4-Anth-2 is 0.759, 0.790, 1.019, and 0.926 eV, respectively. Donor (D = (N, N-diphenyl)) and acceptor (A = (10-(benzofuro[2,3-b] pyridin-6-yl)) in D-π-A system enhances the ΔE (S1-S0) up to 2.837 eV and decreases ΔE (S1-T2) to -0.0635 eV by making it good TADF material. Thermodynamic investigation revealed that the rise in temperature from 50-500 K, CV, CP, internal energy (U), enthalpy (H), entropy (S), and ln (Q) increases, but Gibbs free energy (G) decreases.

Recent advances in atmospheric water harvesting technology and its development

Water scarcity is a pressing issue worldwide. Given the ample atmospheric water sources, water harvesting from the atmosphere presents a promising solution to this challenge. In recent years, the solar-driven atmospheric water harvesting technology utilizing an adsorption-desorption process has garnered considerable interest. This is attributed to the abundant availability of solar energy, advanced adsorbents, improved photothermal materials, sophisticated interface heating system designs, and efficient thermal management techniques, all of which collectively enhance conversion efficiency. This article provides an overview of the advancements in atmospheric water collection, specifically focusing on hygroscopic water harvesting driven by solar energy. The discussion also encompasses the roles of materials, surfaces, equipment, and systems in enhancing water collection efficiency. By outlining both the advantages and challenges of atmospheric water collection, this study aims to shed light on future research directions in this research field.

Cobalt-Ion Superhygroscopic Hydrogels Serve as Chip Heat Sinks Achieving a 5 °C Temperature Reduction via Evaporative Cooling

In the rapidly advancing semiconductor sector, thermal management of chips remains a pivotal concern. Inherent heat generation during their operation can lead to a range of issues such as potential thermal runaway, diminished lifespan, and current leakage. To mitigate these challenges, the study introduces a superhygroscopic hydrogel embedded with metal ions. Capitalizing on intrinsic coordination chemistry, the metallic ions in the hydrogel form robust coordination structures with non-metallic nitrogen and oxygen through empty electron orbitals and lone electron pairs. This unique structure serves as an active site for water adsorption, beginning with a primary layer of chemisorbed water molecules and subsequently facilitating multi-layer physisorption via Van der Waals forces. Remarkably, the cobalt-integrated hydrogel demonstrates the capability to harvest over 1 and 5 g g-1 atmospheric water at 60% RH and 95% RH, respectively. Furthermore, the hydrogel efficiently releases the entirety of its absorbed water at a modest 40°C, enabling its recyclability. Owing to its significant water absorption capacity and minimal dehydration temperature, the hydrogel can reduce chip temperatures by 5°C during the dehydration process, offering a sustainable solution to thermal management in electronics.

Lubricated Surface in a Vertical Double-Sided Architecture for Radiative Cooling and Atmospheric Water Harvesting

Radiative cooling significantly lowers condenser temperatures below ambient levels, enabling atmospheric water harvesting (AWH) without additional energy. However, traditional sky-facing condensers have low cooling power density, and water droplets remain pinned on surface, requiring active condensate collection. To overcome these challenges, a lubricated surface (LS) coating-consisting of highly scalable polydimethylsiloxane elastomer lubricated with silicone oil-is introduced on the condenser side in a vertical double-sided architecture. The design not only effectively doubles the local cooling power, but also eliminates contact-line pinning, enabling passive, gravity-driven collection of water. Robust AWH is demonstrated from a 30 × 30 cm2 sample in outdoor environments (of varying humidity levels and wind speeds in different months) and with no artificial flow of humidified air. In one outdoor test, the passive water collection rate of LS coating reaches 21 g m-2 h-1 double that on superhydrophobic surface, 10 g m-2 h-1. In indoor testing (20 °C and 80% relative humidity), this system achieves a condensation rate ≈87% of the theoretical limit with up to 90% of the total condensate passively collected. this approach achieves effective AWH in a decentralized approach that removes the need for piping infrastructure and external energy input.

A Paper-Based Wearable Moist-Electric Generator for Sustained High-Efficiency Power Output and Enhanced Moisture Capture

Disposable wearable electronics are valuable for diagnostic and healthcare purposes, reducing maintenance needs and enabling broad accessibility. However, integrating a reliable power supply is crucial for their advancement, but conventional power sources present significant challenges. To address that issue, a novel paper-based moist-electric generator is developed that harnesses ambient moisture for power generation. The device features gradients for functional groups and moisture adsorption and architecture of nanostructures within a disposable paper substrate. The nanoporous, gradient-formed spore-based biofilm and asymmetric electrode deposition enable sustained high-efficiency power output. A Janus hydrophobic-hydrophilic paper layer enhances moisture harvesting, ensuring effective operation even in low-humidity environments. This research reveals that the water adsorption gradient is crucial for performance under high humidity, whereas the functional group gradient is dominant under low humidity. The device delivers consistent performance across diverse conditions and flexibly conforms to various surfaces, making it ideal for wearable applications. Its eco-friendly, cost-effective, and disposable nature makes it a viable solution for widespread use with minimal environmental effects. This innovative approach overcomes the limitations of traditional power sources for wearable electronics, offering a sustainable solution for future disposable wearables. It significantly enhances personalized medicine through improved health monitoring and diagnostics.

Enhancement of Water Productivity and Energy Efficiency in Sorption-based Atmospheric Water Harvesting Systems: From Material, Component to System Level

To address the increasingly serious water scarcity across the world, sorption-based atmospheric water harvesting (SAWH) continues to attract attention among various water production methods, due to it being less dependent on climatic and geographical conditions. Water productivity and energy efficiency are the two most important evaluation indicators. Therefore, this review aims to comprehensively and systematically summarize and discuss the water productivity and energy efficiency enhancement methods for SAWH systems based on three levels, from material to component to system. First, the material level covers the characteristics, categories, and mechanisms of different sorbents. Second, the component level focuses on the sorbent bed, regeneration energy, and condenser. Third, the system level encompasses the system design, operation, and synergetic effect generation with other mechanisms. Specifically, the key and promising improvement methods are: synthesizing composite sorbents with high water uptake, fast sorption kinetics, and low regeneration energy (material level); improving thermal insulation between the sorbent bed and condenser, utilizing renewable energy or electrical heating for desorption and multistage design (component level); achieving continuous system operation with a desired number of sorbent beds or rotational structure, and integrating with Peltier cooling or passive radiative cooling technologies (system level). In addition, applications and challenges of SAWH systems are explored, followed by potential outlooks and future perspectives. Overall, it is expected that this review article can provide promising directions and guidelines for the design and operation of SAWH systems with the aim of achieving high water productivity and energy efficiency.

Synergistically Utilizing a Liquid Bridge and Interconnected Porous Superhydrophilic Structures to Achieve a One-Step Fog Collection Mode

Conventional fog collection efficiency is subject to the inherent inefficiencies of its three constituent steps: fog capture, coalescence, and transportation. This study presents a liquid bridge synergistic fog collection system (LSFCS) by synergistically utilizing a liquid bridge and interconnected porous superhydrophilic structures (IPHS). The results indicate that the introduction of liquid bridge not only greatly accelerates water droplet transportation, but also facilitates the IPHS in maintaining rough structures that realize stable and efficient fog capture. During fog collection, the lower section of the IPHS is covered by a water layer, however due to the effect of the liquid bridge, the upper section protrudes out, while covered by a connective thin water film that does not obscure the microstructures of the upper section. Under these conditions, a one-step fog collection mode is realized. Once captured by the IPHS, fog droplets immediately coalesce with the water film, and are simultaneously transported into a container under the effect of the liquid bridge. The LSFCS achieves a collection efficiency of 6.5 kg m-2 h-1, 2.3 times that of a system without a liquid bridge. This study offers insight on improving fog collection efficiency, and holds promise for condensation water collection or droplet manipulation.

Spontaneous water oozing of a soft drain bed via energy-free atmospheric water harvesting

Atmospheric water harvesting has emerged as an efficient strategy for addressing the global challenge of freshwater scarcity. However, the in being energy-consuming water-collecting process has obstructed its practicality. In this work, a soft drain bed, which was composed of hydrophilic cloth and hygroscopic gel, has been demonstrated to capture atmospheric water effectively, followed by converting it into liquid water spontaneously and sustainably, under all-weather humidity conditions. Under the optimal working condition of 30°C with a relative humidity level of 75%, the bed can provide a spontaneous water oozing ability of 1.25 g (liquid water)/hour within the 8 h of working time. More importantly, after 5 working cycles, 80% of the oozing ability can be reserved, suggesting the high potential for practical freshwater supply application. The proposed design strategy is expected to provide new hints for the development of future energy-saving decentralized freshwater supply systems.

Covalent Organic Frameworks for Water Harvesting from Air

Despite approximately 70 % of the earth being covered by water, water shortage has emerged as an urgent social challenge. Sorbent-based atmospheric water harvesting stands out as a potent approach to alleviate the situation, particularly in arid regions. This method requires adsorbents with ample working capacity, rapid kinetics, low energy costs, and long-term stability under operating conditions. Covalent organic frameworks (COFs) are a novel class of crystalline porous materials and offer distinct advantages due to their high specific surface area, structural diversity, and robustness. These properties enable the rational design and customization of their water-harvesting capabilities. Herein, the basic concepts about the water sorption process within COFs, including the parameters that qualitatively or quantitatively describe their water isotherms and the mechanism are summarized. Then, the recent methods used to prepare COFs-based water harvesters are reviewed, emphasizing the structural diversity of COFs and presenting the common empirical understandings of these endeavors. Finally, challenges and research concepts are proposed to help develop next-generation COFs-based water harvesters.

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.

Structure-Property Relationships of Hydrogel-based Atmospheric Water Harvesting Systems

Atmospheric water harvesting (AWH) is considered one of the promising technologies to alleviate the uneven-distribution of water resources and water scarcity in arid regions of the world. Hydrogel-based AWH materials are currently attracting increasing attention due to their low cost, high energy efficiency and simple preparation. However, there is a knowledge gap in the screening of hydrogel-based AWH materials in terms of structure-property relationships, which may increase the cost of trial and error in research and fabrication. In this study, we synthesised a variety of hydrogel-based AWH materials, characterized their physochemcial properties visualized the electrostatic potential of polymer chains, and ultimately established the structure-property-application relationships of polymeric AWH materials. Poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) hydrogel is able to achieve an excellent water adsorption capacity of 0.62 g g-1 and a high water desorption efficiency of more than 90 % in relatively low-moderate humidity environments, which is regarded as one of the polymer materials with potential for future AWH applications.

Unraveling a Stable 16-Ring Aluminophosphate DNL-11 through Three-Dimensional Electron Diffraction for Atmospheric Water Harvesting

Sorption-based atmospheric water harvesting (AWH) is a promising solution for addressing water scarcity. Developing cost-effective and stable water adsorbents with high water uptake capacity and a low-temperature regeneration requirement is a crucially important procedure. In this Communication, we present a novel and stable aluminophosphate (AlPO) molecular sieve (MS) named DNL-11 with 16-ring channels synthesized by using an affordable and commercialized organic structure directing agent (OSDA), whose crystallographic structure is elucidated by three-dimensional electron diffraction (3D ED). DNL-11 exhibits a significant water uptake capacity (189 mg/g) at a very low vapor pressure (5% relative humidity at 30 °C). In addition, most of the adsorbed water can be effortlessly removed by purging N2 at 25 °C under ambient pressure conditions. This may expand the possibility of AWH under extreme drought conditions.

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.

Shaping the Water-Harvesting Behavior of Metal-Organic Frameworks Aided by Fine-Tuned GPT Models

We construct a data set of metal-organic framework (MOF) linkers and employ a fine-tuned GPT assistant to propose MOF linker designs by mutating and modifying the existing linker structures. This strategy allows the GPT model to learn the intricate language of chemistry in molecular representations, thereby achieving an enhanced accuracy in generating linker structures compared with its base models. Aiming to highlight the significance of linker design strategies in advancing the discovery of water-harvesting MOFs, we conducted a systematic MOF variant expansion upon state-of-the-art MOF-303 utilizing a multidimensional approach that integrates linker extension with multivariate tuning strategies. We synthesized a series of isoreticular aluminum MOFs, termed Long-Arm MOFs (LAMOF-1 to LAMOF-10), featuring linkers that bear various combinations of heteroatoms in their five-membered ring moiety, replacing pyrazole with either thiophene, furan, or thiazole rings or a combination of two. Beyond their consistent and robust architecture, as demonstrated by permanent porosity and thermal stability, the LAMOF series offers a generalizable synthesis strategy. Importantly, these 10 LAMOFs establish new benchmarks for water uptake (up to 0.64 g g-1) and operational humidity ranges (between 13 and 53%), thereby expanding the diversity of water-harvesting MOFs.

Understanding and Utilizing Droplet Impact on Superhydrophobic Surfaces: Phenomena, Mechanisms, Regulations, Applications, and Beyond

Droplet impact is a ubiquitous liquid behavior that closely tied to human life and production, making indispensable impacts on the big world. Nature-inspired superhydrophobic surfaces provide a powerful platform for regulating droplet impact dynamics. The collision between classic phenomena of droplet impact and the advanced manufacture of superhydrophobic surfaces is lighting up the future. Accurately understanding, predicting, and tailoring droplet dynamic behaviors on superhydrophobic surfaces are progressive steps to integrate the droplet impact into versatile applications and further improve the efficiency. In this review, the progress on phenomena, mechanisms, regulations, and applications of droplet impact on superhydrophobic surfaces, bridging the gap between droplet impact, superhydrophobic surfaces, and engineering applications are comprehensively summarized. It is highlighted that droplet contact and rebound are two focal points, and their fundamentals and dynamic regulations on elaborately designed superhydrophobic surfaces are discussed in detail. For the first time, diverse applications are classified into four categories according to the requirements for droplet contact and rebound. The remaining challenges are also pointed out and future directions to trigger subsequent research on droplet impact from both scientific and applied perspectives are outlined. The review is expected to provide a general framework for understanding and utilizing droplet impact.