Viability of a practical multicyclic sorption-based water harvester with improved water yield

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

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

Towards a better understanding of atmospheric water harvesting (AWH) technology

Atmospheric water harvesting (AWH) technology is an emerging sustainable development strategy to deal with global water scarcity. To better understand the current state of AWH technology development, we conducted a bibliometric analysis highlighting three water harvesting technologies (fog harvesting, condensation, and sorption). By comprehensively reviewing the research progress and performing a comparative assessment of these technologies, we summarized past achievements and critically analyzed the different technologies. Traditional fog collectors are more mature, but their efficiency still needs to be improved. External field-driven fog harvesting and active condensation need to be driven by external forces, and passive condensation has high requirements for environmental humidity. Emerging bio-inspired fog harvesting and sorption technology provide new possibilities for atmospheric water collection, but they have high requirements for materials, and their commercial application is still to be further promoted. Based on the key characteristics of each technology, we presented the development prospects for the joint use of integrated/hybrid systems. Next, the water-energy relationship is used as a link to clarify the future development strategy of AWH technology in energy driving and conversion. Finally, we outlined the core ideas of AWH for both basic research and practical applications and described its limitless possibilities for drinking water supply and agricultural irrigation. This review provides an essential reference for the development and practical application of AWH technologies, which contribute to the sustainable utilization of water resources globally.

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.

All-Day Multicyclic Atmospheric Water Harvesting Enabled by Polyelectrolyte Hydrogel with Hybrid Desorption Mode

Sorption-based atmospheric water harvesting (AWH) is a promising approach for mitigating worldwide water scarcity. However, reliable water supply driven by sustainable energy regardless of diurnal variation and weather remains a long-standing challenge. To address this issue, a polyelectrolyte hydrogel sorbent with an optimal hybrid-desorption multicyclic-operation strategy is proposed, achieving all-day AWH and a significant increase in daily water production. The polyelectrolyte hydrogel possesses a large interior osmotic pressure of 659 atm, which refreshes sorption sites by continuously migrating the sorbed water within its interior, and thus enhancing sorption kinetics. The charged polymeric chains coordinate with hygroscopic salt ions, anchoring the salts and preventing agglomeration and leakage, thereby enhancing cyclic stability. The hybrid desorption mode, which couples solar energy and simulated waste heat, introduces a uniform and adjustable sorbent temperature for achieving all-day ultrafast water release. With rapid sorption-desorption kinetics, an optimization model suggests that eight moisture capture-release cycles are capable of achieving high water yield of 2410 mLwater kgsorbent -1 day-1 , up to 3.5 times that of single-cyclic non-hybrid modes. The polyelectrolyte hydrogel sorbent and the coupling with sustainable energy driven desorption mode pave the way for the next-generation AWH systems, significantly bringing freshwater on a multi-kilogram scale closer.

Hygroscopic Porous Polymer for Sorption-Based Atmospheric Water Harvesting

Sorption-based atmospheric water harvesting (SAWH) holds huge potential due to its freshwater capabilities for alleviating water scarcity stress. The two essential parts, sorbent material and system structure, dominate the water sorption-desorption performance and the total water productivity for SAWH system together. Attributed to the superiorities in aspects of sorption-desorption performance, scalability, and compatibility in practical SAWH devices, hygroscopic porous polymers (HPPs) as next-generation sorbents are recently going through a vast surge. However, as HPPs' sorption mechanism, performance, and applied potential lack comprehensive and accurate guidelines, SAWH's subsequent development is restricted. To address the aforementioned problems, this review introduces HPPs' recent development related to mechanism, performance, and application. Furthermore, corresponding optimized strategies for both HPP-based sorbent bed and coupling structural design are proposed. Finally, original research routes are directed to develop next-generation HPP-based SAWH systems. The presented guidelines and insights can influence and inspire the future development of SAWH technology, further achieving SAWH's practical applications.

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.

Prospects for Simultaneously Capturing Carbon Dioxide and Harvesting Water from Air

Mitigation of anthropogenic climate change is expected to require large-scale deployment of carbon dioxide removal strategies. Prominent among these strategies is direct air capture with sequestration (DACS), which encompasses the removal and long-term storage of atmospheric CO₂  by purely engineered means. Because it does not require arable land or copious amounts of freshwater, DACS is already attractive in the context of sustainable development, but opportunities to improve its sustainability still exist. Leveraging differences in the chemistry of CO₂  and water adsorption within porous solids, here, the prospect of simultaneously removing water alongside CO₂  in direct air capture operations is investigated. In many cases, the co-adsorbed water can be desorbed separately from chemisorbed CO₂  molecules, enabling efficient harvesting of water from air. Depending upon the material employed and process conditions, the desorbed water can be of sufficiently high purity for industrial, agricultural, or potable use and can thus improve regional water security. Additionally, the recovered water can offset a portion of the costs associated with DACS. In this Perspective, molecular- and process-level insights are combined to identify routes toward realizing this nascent yet enticing concept.