Confined water-selective highways in a densified photothermal membrane enable ultrafast purification of complex wastewater

Confined water-selective highways in a densified photothermal membrane enable ultrafast purification of complex wastewater | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Confined water-selective highways in a densified photothermal membrane enable ultrafast purification of complex wastewater Panpan Zhang, Jie Li, Qiang Jia, Shijie Xing, Jingtao Bi, Lei Wang, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8090933/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Solar-driven interfacial evaporation (SDIE) is a sustainable, carbon-neutral approach for freshwater production. Nevertheless, achieving both high evaporation rates and efficient removal remains challenging, especially for wastewater enriched with concentrated ions and strongly polar VOCs from chemical and electronics manufacturing. Here, we report the confined water-selective highways within a densified photothermal membrane (DPM) for ultrafast purification of such complex wastewater. Through mechanical compression and the rational selection of hydrophilic polymers, DPM’s interlayer nanostructures and chemical environments are engineered with molecular precision. Due to the synergistic effect of steric hindrance and chemical selectivity, this structure enables preferential water transport while effectively excluding highly concentrated ions and strongly polar VOCs. DPM exhibits a high water evaporation rate of 2.58 kg m − 2 h − 1 under 1 kW m − 2 . DPM retains stable performance for over 200 h in various near-saturated hypersaline solutions (20 wt% salinity) and enables clean water harvesting from both common (e.g., benzene, toluene, phenol) and strongly polar VOCs (e.g., ethanol, isopropanol, n-butanol) even at very high concentrations. Device integration further demonstrates its scalability for treating complex wastewater, highlighting the significance of molecularly engineered interfacial architectures for efficient SDIE under challenging conditions. Scientific community and society/Water resources Earth and environmental sciences/Environmental social sciences/Sustainability Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Severe water scarcity is a mounting global challenge that demands sustainable water purification technologies 1 – 3 . Solar-driven interfacial evaporation (SDIE) offers a clean and energy-efficient strategy for producing clean water 4 – 7 . Recent advances have led to the development of diverse photothermal materials capable of treating complex wastewater 8 , 9 . In particular, the application of SDIE systems to treat complex wastewater with high salinity and strong polarity, primarily originating from key industries such as petrochemical, pharmaceutical, and electronics manufacturing, has become a current research focus 10 – 12 . However, photothermal materials specifically designed for these challenging wastewaters remain scarce, as simultaneously achieving a high water evaporation rate, excellent removal efficiency, and long-term stability is highly demanding 13 , 14 . On one hand, in the SDIE system, addressing highly saline wastewater usually involves non-volatile contaminants, such as various salt ions. These substances remain in the residual water and do not evaporate with water molecules 15 , 16 . During evaporation, these non-volatile contaminants tend to crystallize and accumulate on the photothermal materials, potentially degrading performance over time. Strategies including convective/diffusive reflow, non-contact configurations, and ionic diffusion equilibrium have been explored to mitigate salt accumulation during SDIE 17 – 19 . While partially effective, these approaches often incur substantial heat losses, block water transport pathways, and suffer from electrostatic shielding effects, ultimately limiting the water evaporation rate 20 – 22 . Thus, efficient and sustainable solutions to salt buildup in SDIE remain urgently needed for treating hypersaline wastewater. On the other hand, removal of volatile organic compounds (VOCs) such as toluene, phenol, and trichloroethylene from wastewater has been investigated via air stripping 23 , 24 , adsorption 25 , 26 , photocatalytic degradation 27 , 28 , pervaporation 29 , 30 , and membrane sieving 31 , 32 . Among these, membrane-based photothermal materials offer notable advantages, including enhanced removal efficiency, operational simplicity, and independence from added chemicals or catalysts 33 – 35 . However, these photothermal materials typically exhibit a low water evaporation rate of no more than 1.53 kg m – 2 h – 1 under 1 kW m − 2 and limited efficacy at VOC concentrations exceeding 400 mg L – 1 . Furthermore, few studies have addressed the treatment of strongly polar VOCs, including ethanol, isopropanol, and n-butanol, particularly those originating from the electronics and semiconductor manufacturing industries. Collectively, these challenges highlight the pressing need to precisely engineer the interfacial nanostructure and surface chemistry of photothermal materials for efficient treatment of complex wastewater containing highly concentrated ions and strongly polar VOCs. Notably, VOCs removal in membrane-based photothermal materials primarily relies on molecular sieving effects governed by nanopore size and surface functional group affinity 36 – 38 . Strong intermolecular interactions between water and VOCs, particularly strongly polar species such as ethanol, isopropanol, and n-butanol, pose significant challenges for separation processes. Even at trace levels, these substances still present serious risks to ecosystems and human health 39 , 40 . Consequently, the design of next-generation photothermal materials capable of simultaneously achieving rapid water evaporation and selective removal of highly saline and polar VOCs wastewater represents a critical frontier in water purification technologies. The overall heat transfer and water evaporation performance of the SDIE system is largely governed by the thickness and area of the evaporative thin-film region. Photothermal interfaces engineered with “nanostructure confinement” and “surface confinement” architectures offer precise control over water transport, evaporation energy input, and phase-change dynamics 41 , 42 . For instance, nanoscale channels can significantly expand the solid-liquid interfacial area, where interfacial interactions profoundly influence liquid behavior under confinement. The evaporation energy required at the solid-liquid interface within nanostructures is markedly lower than that at the liquid-vapor interface center, thereby enhancing evaporation within nanoporous domains 43 – 45 . Moreover, the nanopore size and surface functional group affinity of photothermal interfaces define selective water transport pathways, enabling efficient exclusion of salt ions and strongly polar VOCs through synergistic effects of size sieving and strong hydration interactions 41 . As such, achieving efficient water/ions and water/VOCs separation while maintaining a high water evaporation rate requires photothermal membrane interlayer nanostructures and chemical environments engineered with molecular precision. Here, a densified photothermal membrane (DPM) with confined water-selective highways is reported for ultrafast and efficient purification of wastewater containing highly concentrated ions and strongly polar VOCs. Through mechanical compression of graphene architecture and strategic selection of hydrophilic polymers, the DPM’s interlayer nanostructures and chemical environments are tailored with molecular precision. This architecture promotes selective water transport while effectively rejecting a broad spectrum of highly concentrated ions and strongly polar VOCs due to the synergistic effect of steric hindrance and chemical selectivity. The design of the DPM is guided by three key principles: (1) utilizing mechanical compression to regulate the densification of the graphene framework, thereby better balancing water mass transfer, heat loss, and evaporation rate; (2) rationally selecting hydrophilic polymers that form strong interactions with water molecules, establishing confined water-selective highways; and (3) coordinating the size-sieving effects of graphene interlayer nanostructures and the stable hydration layers formed by hydrophilic polymers, to achieve efficient removal of highly concentrated ions and strongly polar VOCs (Fig. 1 ). Under 1 kW m − 2 illumination, DPM achieves a high water evaporation rate of up to 2.58 kg m − 2 h − 1 . Simultaneously, the DPM exhibits stable operation for more than 200 h in diverse near-saturated hypersaline solutions (20 wt% salinity), while enabling the clean water production from both common (e.g., benzene, toluene, phenol, rejection rate ˃99.99%) and strongly polar VOCs (e.g., ethanol, isopropanol, n-butanol, rejection rate ˃99.0%) at high concentrations. These findings demonstrate the critical importance of molecular-level interfacial engineering in advancing high-performance SDIE for complex wastewater purification. Results and discussion Preparation and characterization To fabricate the DPM, a mixture of graphene oxide (GO) and hydrophilic polymers was horizontal directional freeze-dried to obtain a three-dimensional framework, which was then subjected to mechanical compression, thermal annealing, and chemical crosslinking (Fig. 2a). We employ tunable mechanical compression (5–15 MPa, 2 min) and a series of hydrophilic polymers bearing distinct functional groups, including amide (acrylamide) (AAm), hydroxyl (trehalose) (Tre), carboxyl (sodium alginate) (SA), and sulfonate (2-acrylamido-2-methylpropane sulfonic acid sodium salt) (AMPS), to precisely tailor the interlayer nanostructures and chemical environments of DPM. The resulting samples are denoted as DPM n -X, where n represents the applied mechanical compression strength (5–15 MPa), and X denotes the incorporated hydrophilic polymer (PAAm, Tre, SA, and PAMPS), respectively. Upon mechanical compression, the thickness of the 3D graphene foam is significantly reduced, transforming into a densified membrane structure (Fig. 2b and Supplementary Fig. S1 ). As a representative example, scanning electron microscope (SEM) images reveal that the interlayer nanostructures of DPM n -PAMPS gradually shrink with increasing mechanical compression strength, exhibiting a more compact architecture. However, all DPM n -PAMPS remain less compact than the vacuum-filtrated counterpart (DPM F -PAMPS) (Supplementary Fig. S2). The degree of interlayer densification plays a critical role in regulating water transport, thermal losses, and water evaporation performance 46 – 48 . In the case of DPM 5 -PAMPS, the loosely packed structure permits excessive water flow and heat dissipation, thereby reducing the water evaporation rate. Conversely, DPM 15 -PAMPS and DPM F -PAMPS show overly compacted Figure 2 | Preparation process and characterizations. a Schematic illustration of the fabrication process of the DPM. b Photograph of a DPM 10 -PAMPS sample before (left) and after (right) mechanical compression. SEM images of ( c ) PM 0 -PAMPS and ( d ) DPM 10 -PAMPS at different magnifications. e FTIR of DPM 10 -PAAm, DPM 10 -Tre, DPM 10 -SA, and DPM 10 -PAMPS, respectively. f EDS, ( g ) C1s, and ( h ) S2p XPS spectra of DPM 10 -PAMPS. architectures that restrict water transport, also resulting in reduced water evaporation rate. Notably, DPM 10 -PAMPS achieves an optimal balance, enabling adequate water transport, minimal heat losses, and a high evaporation rate (Supplementary Fig. S3, 10 MPa is the optimal mechanical compressive strength). This DPM 10 -PAMPS can be fabricated over a large area and appears visibly black, contributing to excellent light absorption (Supplementary Fig. S4). SEM images confirm that DPM 10 -PAAm, DPM 10 -Tre, DPM 10 -SA, and DPM 10 -PAMPS all exhibit significantly densified interlayer nanostructures, in contrast to the non-compressed composites (PM 0 -PAMPS), which display loose frameworks (Fig. 2c,d and Supplementary Fig. S5). Fourier-transform infrared spectroscopy (FTIR) analysis reveals distinct peaks for DPM 10 - PAAm at 3360, 1660, and 1420 cm − 1 , corresponding to N–H stretching, C = O stretching, and C–N stretching vibrations, respectively, confirming the presence of –CONH 2 groups (Fig. 2e) 49 . For DPM 10 -Tre, a broad band at 3200–3600 cm − 1 and a peak at 1030 cm − 1 are assigned to O–H and C–O–C stretching vibrations, indicating successful –OH modification. DPM 10 -SA exhibits characteristic –COO⁻ asymmetric and symmetric stretching vibrations at 1600 and 1410 cm − 1 , respectively, along with a C–O–C stretching vibration at 1030 cm − 1 , verifying the incorporation of –COO⁻ 35 . DPM 10 -PAMPS exhibits three strong absorption peaks at 1350, 1200, and 1050 cm − 1 , representing the characteristic peaks of the sulfonate, confirming the loading of –SO 3 ⁻ groups 49 . These results are further supported by energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), which confirm the successful functionalization of hydrophilic groups –CONH 2 , –OH, –COO⁻, and –SO 3 ⁻ in DPM 10 -PAAm, DPM 10 -Tre, DPM 10 -SA, and DPM 10 -PAMPS, respectively (Fig. 2f–h, and Supplementary Figs. S6–9). Confined water-selective highways in DPM-X The interlayer nanostructures and chemical environments regulation of DPM 10 -X with molecular precision can form the confined water-selective highways. By coupling the size-sieving effect of graphene interlayers with strong water interaction derived from hydrophilic polymers, the DPM 10 -X achieves ultrafast purification of wastewater containing high salinity and polar VOCs. Among them, the interlayer hydrophilic functional groups of the DPM 10 -X play a pivotal role in mediating interactions with water molecules. The interactions between water molecules and DPM 10 -PAAm or DPM 10 -Tre are primarily governed by hydrogen bonding, with the abundant –OH groups in DPM 10 -Tre exhibiting stronger binding affinity toward water. In contrast, DPM 10 -SA and DPM 10 -PAMPS engage in both hydrogen bonding and ion-dipole interactions with water molecules, leading to further enhanced water affinity. Notably, the strong ion-dipole interactions between –SO 3 ⁻ groups in DPM 10 -PAMPS and water have higher bond strength and lower directionality, resulting in higher affinity for water molecules. Electrostatic potential mapping reveals that PAMPS molecules, characterized by their high density of –SO 3 ⁻ groups, provide abundant binding sites for water molecules, enabling preferential water transport (Fig. 3 a and Supplementary Fig. S10) 50 . Consistently, density functional theory (DFT) calculations show that PAMPS-water exhibits the highest binding energy (84.78 kJ mol − 1 ), significantly exceeding those of SA-water (75.35 kJ mol − 1 ), Tre-water (61.46 kJ mol − 1 ), and PAAm-water (49.37 kJ mol − 1 ) (Fig. 3 b). These results confirm the strongest water affinity of DPM 10 -PAMPS, which is favorable for constructing confined water-selective highways within the graphene interlayer nanostructures for ultrafast purification of wastewater containing highly concentrated ions and strongly polar VOCs. Additionally, the hydrophilic functional groups at the photothermal interface can regulate the water states within the DPM 10 -X, thereby influencing water transport behavior and evaporation rate 43 . Among all samples, DPM 10 -PAMPS exhibits the highest saturated water content (0.73 g g − 1 ), yet it remains significantly lower than that of conventional hydrogels, indicating its strongest affinity toward water molecules (Fig. 3 c). It also exhibits the lowest water contact angle (44.7°), suggesting enhanced water transport performance compared to the other samples (Fig. 3 d). Differential scanning calorimetry (DSC) measurements of melting enthalpy reveal that, compared to pure water, the onset melting points of DPM 10 -PAAm, DPM 10 -Tre, DPM 10 -SA, and DPM 10 -PAMPS all shift below 0°C, indicating the coexistence of freezable and non-freezable water within the materials (Fig. 3 e). Among them, DPM 10 -PAMPS exhibits the highest melting enthalpy, likely due to a greater proportion of intermediate water (IW) arising from its stronger affinity toward water molecules. This was further supported by Raman spectroscopy, where DPM 10 -PAMPS displays the highest IW/FW ratio (0.164), suggesting enhanced interaction with water that promotes the formation of IW (Fig. 3 f and Supplementary Fig. S11). The increased IW content facilitates water activation and lowers the energy required for evaporation. As a result, DPM 10 -PAMPS achieves remarkably low water evaporation enthalpy of 1224.30 J g − 1 , significantly lower than that of pure water (2440.0 J g − 1 ), as well as DPM 10 -PAAm (1875.07 J g − 1 ), DPM 10 -Tre (1372.82 J g − 1 ), and DPM 10 -SA (1329.63 J g − 1 ) (Fig. 3 g,h). Consequently, the abundant –SO 3 ⁻ in DPM 10 -PAMPS enables strong ion-dipole and hydrogen-bonding interactions with water molecules, offering abundant binding sites and facilitating the formation of confined water-selective highways. The confined water transport in DPM 10 -PAMPS is primarily governed by strong interactions between hydrophilic polymers and water molecules. Specifically, the ion-dipole interactions between –SO 3 ⁻ and water are stronger than the hydrogen bonding among water molecules, leading to preferential transport of water into DPM 10 -PAMPS and its association with hydrophilic polymer chains. Under sunlight, the bound water is subsequently transported toward the evaporation interface via hydrogen-bond networks (Fig. 3 i). Therefore, benefiting from the graphene interlayer nanostructures and precisely regulated chemical environments, the confined water-selective highways in DPM 10 -PAMPS not only enable ultrafast water transport, but also achieve effective removal of highly concentrated ions and strongly polar VOCs based on size-sieving and strong hydration effects. SDIE performance and treatment of hypersaline solutions Benefiting from the excellent light-harvesting property of graphene, DPM 10 -X exhibits strong broadband solar absorption across the full solar spectrum (250–2500 nm). Under 1kW m − 2 , the surface temperatures of DPM 10 -PAAm, DPM 10 -Tre, DPM 10 -SA, and DPM 10 -PAMPS rapidly increase within 5 min and stabilize at 51.5–52.5°C, indicating efficient photothermal conversion performance (Fig. 4 a). Through mechanical compression combined with chemical modification using hydrophilic polymers, the graphene interlayer nanostructures are precisely tuned. According to X-ray diffraction (XRD) analysis, the interlayer spacing of DPM 10 -X is maintained in the narrow range of 6.31–6.41 Å (Fig. 4 b). This interlayer spacing is sufficiently small to effectively exclude hydrated salt ions such as Na⁺ (hydrated radius 3.58 Å) and Cl⁻ (3.32 Å), while permitting efficient water molecule transport, thereby endowing the material with excellent salt-rejection capabilities (Fig. 4 c). Under 1 kW m − 2 , DPM 10 -PAMPS achieves a maximum water evaporation rate of 2.58 kg m − 2 h − 1 in pure water (Fig. 4 d). Based on this superior performance, DPM 10 -PAMPS is further selected for SDIE tests under varying salinities, including pure water and saline solutions with 3.5 wt%, 10 wt%, and 20 wt% NaCl. Although the water evaporation rate decreases with increasing salt concentration, DPM 10 -PAMPS still maintains a high evaporation rate of 1.50 kg m − 2 h − 1 even in near-saturated 20 wt% NaCl, significantly outperforming the evaporation rate of pure water under the same conditions (Fig. 4 e). Meanwhile, DPM 10 -PAMPS is also applicable for treating complex saline solutions containing various heavy metal ions. In hypersaline solutions with salinities of 5 wt%, 10 wt%, 15 wt%, and 20 wt%, where Cr 3+ , Pb 2+ , Zn 2+ , Ni 2+ , and Cu 2+ are present in an equal mass ratio of 1:1:1:1:1. The corresponding water evaporation rates reach 2.13, 1.99, 1.81, and 1.76 kg m − 2 h − 1 , respectively (Fig. 4 f). Notably, the water evaporation rates in these multicomponent heavy metal solutions are slightly higher than those observed in NaCl solutions of equivalent salinity. This enhancement is likely due to the strong hydration interactions between Na⁺/Cl⁻ ions and water molecules, which significantly reduce the fraction of free water available for evaporation. In contrast, mixed heavy metal ions such as Cr 3+ , Pb 2+ , Zn 2+ , Ni 2+ , and Cu 2+ exhibit diverse hydration capabilities and compete for coordination with water molecules. Such ion-ion and ion-solvent interactions disrupt the ordered hydration structures, leading to a reduced overall hydration degree and an increased proportion of free water, thereby facilitating faster evaporation. To evaluate its long-term operational stability in highly saline environments, continuous water evaporation tests were performed under 1 kW m − 2 , with 8 h operation cycles. Remarkably, after 200 h of ongoing testing, DPM 10 -PAMPS retains a steady water evaporation rate of 1.50 kg m − 2 h − 1 , demonstrating excellent salt resistance and operational durability (Fig. 4 g). Purifying both common and strongly polar VOCs VOCs, many of which are highly toxic, are widely present throughout the water cycle. However, their complex physicochemical properties make their separation from water extremely challenging 51 – 53 . While certain aromatic VOCs exhibit low aqueous solubility, their inherent volatility allows them to persist in trace amounts, posing serious risks to both human health and the environment. In contrast, most phenolic and alcoholic VOCs possess strong hydrophilicity. Their polarity, which closely resembles that of water, along with the formation of azeotropes, renders conventional separation methods ineffective 54 , 55 . By precisely tuning the graphene interlayer nanostructures and chemical environments of DPM 10 -PAMPS, confined water-selective highways have been established, demonstrating promising potential for the efficient separation of water/VOCs mixtures. The optimized DPM 10 -PAMPS was integrated into a custom-designed sealed device to purify aqueous solutions containing VOCs. In this setup, the water/VOCs solution was introduced from the bottom chamber, while the top chamber was connected to a condenser-cooled vessel to collect the generated water vapor. The effective water evaporation area of DPM 10 -PAMPS was 20 mm × 20 mm (Fig. 5 a and Supplementary Fig. S12). Under solar irradiation, the elevated interfacial temperature provides a strong driving force for the selective evaporation of water molecules. Two representative classes of VOCs were selected for evaluation, including common aromatic VOCs (benzene, toluene, phenol) and strongly polar alcoholic VOCs (ethanol, isopropanol, and n-butanol). The purification performance of DPM 10 -PAMPS in the water/VOCs system is closely associated with both the molecular size of the VOCs and their intermolecular interactions with water. Compared with hydrated ions, VOC molecules are significantly larger in size, enabling preliminary size-based exclusion via the compact interlayer nanostructures of graphene constructed through mechanical compression. However, the separation becomes increasingly challenging for VOCs exhibiting stronger interactions with water molecules. The intermolecular interactions of water-VOCs generally follow the order of benzene < toluene < phenol < n-butanol < isopropanol < ethanol < water. Alcoholic VOCs, in particular, exhibit strong hydrogen bonding and form azeotropes with water, further complicating their separation. DFT calculations reveal that the interaction energy of PAMPS-water molecules is substantially stronger than that with VOCs molecules, including benzene, toluene, phenol, n-butanol, isopropanol, and ethanol (Fig. 5 b,c, and Supplementary Fig. S13). To gain a deeper understanding of the underlying mechanism, MD simulations were conducted to investigate the molecular diffusion behavior in the model based on DPM 10 -PAMPS (Supplementary Fig. S14). Given the strongest intermolecular interactions between water and ethanol, we selected their mixture as a representative strongly polar VOC system for the MD simulations. The results show that DPM 10 -PAMPS displays preferential water transport while effectively excluding ethanol (Fig. 5 d and Supplementary Fig. S15). No ethanol molecules are observed in the snapshot, demonstrating the excellent elimination performance of ethanol from water using DPM 10 -PAMPS. The mean square displacement (MSD) curve over time reveals that, compared with ethanol, water exhibits superior diffusion behavior in DPM 10 -PAMPS (Fig. 5 e and Supplementary Fig. S16). Simultaneously, the density profiles of water and ethanol at different positions demonstrate that only water molecules selectively transport across the DPM 10 -PAMPS, whereas ethanol molecules are effectively retained (Fig. 5 f and Supplementary Fig. S17), demonstrating the excellent performance of DPM 10 -PAMPS in purifying water/ethanol mixtures. These MD simulations confirm that precise regulation of the interlayer nanostructures and chemical environments in DPM 10 -PAMPS facilitates selective water transport while efficiently rejecting a wide range of strongly polar VOCs, owing to the synergistic effects of steric hindrance and chemical selectivity 50 , 56 . We evaluated the separation performance of DPM 10 -PAMPS in water/aromatic VOCs (benzene, toluene, and phenol) with varying VOC concentrations (100, 300, 500, and 1000 ppm). Across all tested concentrations, DPM 10 -PAMPS exhibits a high water evaporation rate along with excellent VOCs removal efficiencies as high as 99.99% (Fig. 6 a − c, standard curves of aromatic VOCs are shown in Supplementary Fig. S18). Whether the high carcinogenic benzene or irritants like toluene and phenol, the VOC concentrations in generated water vapor are all below the health-drinking water criteria recommended by the World Health Organization (WHO) and U.S. Environmental Protection Agency (US-EPA) (Supplementary Table S1 ). Notably, even at a high concentration of 1000 ppm (e.g., phenol), the rejection efficiency reaches up to 99.99%, significantly outperforming previously reported photothermal membranes for VOCs removal (Supplementary Table S2) 57 , 58 . Even in complex VOC systems where benzene, toluene, and phenol are present simultaneously, DPM 10 -PAMPS also demonstrated excellent elimination efficiency across all tested concentrations, achieving consistent removal of residual benzene (0.001–0.004 ppm), toluene (0.017–0.027 ppm), and phenol (0.01–0.05 ppm) in these multicomponent solutions (Supplementary Fig. S19). Additionally, DPM 10 -PAMPS was tested in water/alcoholic VOCs, comprising strongly polar species, including ethanol, isopropanol, and n-butanol (standard curves of alcoholic VOCs are shown in Supplementary Fig. S20). These mixtures contain alcoholic VOCs mass fractions ranging from 30 to 90 wt%. Despite the high alcoholic VOCs content, DPM 10 -PAMPS achieves a high water evaporation rate and the resultant water content ranging from 99.50 wt% to 99.72 wt% for all tested alcoholic VOCs (rejection rate ˃99.0%), demonstrating its outstanding separation capability (Supplementary Fig. S21). The separation performance of DPM 10 -PAMPS is evaluated using the separation factor ( α ), as defined by the following equations 59 : $$\:\begin{array}{c}\text{α}\text{=}\frac{{\text{P}}_{\text{W}}/{\text{P}}_{\text{E}}}{{\text{F}}_{\text{W}}/{\text{F}}_{\text{E}}}\#\text{(}\text{1}\text{)}\end{array}$$ Here, P W and P E denote the mass fractions of water and alcoholic VOCs in the collected water, while F W and F E represent the corresponding mass fractions in the feed solution. Based on these calculations, DPM 10 -PAMPS achieves separation factors as high as 2638, 2186, and 2299 for water/ethanol, water/isopropanol, and water/n-butanol mixtures, respectively (with an initial water/alcoholic VOCs mass ratio of 1:9) (Fig. 6 d − f), demonstrating superior performance over previously reported membranes in alcoholic VOCs separation (Supplementary Tables S3 − 5). Furthermore, in the complex water/alcoholic VOCs solutions with 30 wt%, 60 wt%, and 90 wt% (where ethanol, isopropanol, and n-butanol are present in an equal mass ratio of 1:1:1), the resultant water content reaches more than 99.52%, demonstrating the outstanding separation performance of DPM 10 -PAMPS (Supplementary Fig. S22). Compared with other state-of-the-art membranes previously reported for water/alcoholic VOCs separations, DPM 10 -PAMPS exhibits a remarkable advantage in the selective removal of alcoholic VOCs (Fig. 6 g–i and Supplementary Figs. S23–25). Outdoor scaled-up performance evaluation To evaluate the practical applicability of DPM 10 -PAMPS for treating highly challenging complex wastewater, we designed and scaled up a device for validation under outdoor conditions (Fig. 7 a). The scaled-up device is constructed from polytetrafluoroethylene with dimensions of 0.4 m × 0.4 m (effective evaporation area of 0.04 m 2 ). The lower water supply layer incorporates microchannels to ensure adequate water delivery. Circulating air was introduced into the upper layer to efficiently transport clean water vapor to the collection bottles placed in the condensate, while preventing condensation on the glass of the light-transmitting layer. This approach avoids reduced light absorption and low water evaporation rates. The complex wastewater feed contained mixed salt ions as well as aromatic and alcoholic VOCs, including Na + (50,000 ppm), Cu 2+ (50,000 ppm), toluene (500 ppm), phenol (1000 ppm), ethanol (50,000 ppm), and n-butanol (50,000 ppm). Throughout the outdoor tests, ambient temperature, solar intensity, surface temperature, and evaporation rates were monitored in real time from 9:00 to 17:00, November 2, 2025 (Fig. 7 b,c). DPM 10 -PAMPS shows a higher surface temperature compared to complex wastewater. It also exhibits a favorable water evaporation rate under low solar intensity and ambient outdoor temperatures (Fig. 7 d). Benefiting from the synergistic effect of steric hindrance and chemical selectivity, DPM 10 -PAMPS promotes selective water transport while effectively rejecting a broad spectrum of highly concentrated ions and strongly polar VOCs (Fig. 7 e). Under low solar irradiance and ambient winter temperatures, the DPM 10 -PAMPS-based device achieves an outdoor clean water collection output of 5.75 kg m − 2 day − 1 from a complex wastewater system. Meanwhile, DPM 10 -PAMPS exhibits excellent removal efficiencies for various contaminants, reaching 99.99% (Na + ), 99.99% (Cu 2+ ), 99.97% (toluene), 99.99% (phenol), 99.40% (ethanol), and 99.36% (n-butanol), respectively (Fig. 7 f). This work highlights the potential of DPM 10 -PAMPS for scalable and robust SDIE applications in challenging real-world conditions. Discussion We report a DPM with confined water-selective highways that enables ultrafast purification of wastewater containing highly concentrated ions and strongly polar VOCs. Through the synergistic design of mechanical compression and hydrophilic polymer selection, DPM offers confined water-selective highways that facilitate rapid and selective water transport while effectively excluding both highly concentrated ions and strongly polar VOCs. The DPM demonstrates a high water evaporation rate of up to 2.58 kg m − 2 h − 1 under 1 kW m − 2 . DPM maintains stable performance for over 200 h in various near-saturated hypersaline solutions (20 wt% salinity) and enables the production of clean water from both common and strongly polar VOCs, even at very high concentrations. Integration of DPM with the device validates the scaling-up feasibility of this approach for treating complex wastewater. These findings highlight the potential of nanoscale structural confinement and chemical microenvironment tuning in advancing SDIE-based technologies toward practical, high-performance water purification, particularly under conditions involving hypersaline and VOC-laden wastewater. Methods Preparation of DPM n -X Graphene oxide (GO) was synthesized via a modified Hummers method. To prepare the mixed dispersion, a hydrophilic polymer solution (5 wt%) was introduced into the GO suspension (7.0 mg mL − 1 ) at a volume ratio of 1:9, followed by thorough homogenization under ultrasonication. A certain amount of ethanol was added to the mixed solution to reduce the surface tension and regulate the oriented ice crystal growth rate. The resulting dispersion was rapidly pre-frozen horizontally in liquid nitrogen and subsequently freeze-dried (BIOCOOL, FD-1A-50+) to sublimate the ice under low temperature and pressure, yielding three-dimensional (3D) GO/hydrophilic polymer aerogels with interconnected porous architectures. The as-prepared aerogels were compressed under uniaxial pressure (5–15 MPa) to form freestanding two-dimensional (2D) membranes. Subsequently, thermal annealing (200°C, 2 h) was employed to reduce GO, enhancing the structural stability of the densified photothermal membrane (DPM). Different crosslinking strategies were employed for various DPMs. Specifically, for samples containing acrylamide (AAm) and 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS), photo-crosslinking was performed by immersing the membranes in an aqueous solution of ammonium persulfate ((NH 4 ) 2 S 2 O 8 , 0.1 mol L − 1 , 200 µL) as the initiator and N,N’-methylenebisacrylamide (MBAA, 0.1 mol L − 1 , 30 µL) as the crosslinker, followed by UV irradiation for 2 h. Sodium alginate (SA)-added DPMs were ionically crosslinked in CaCl 2 solution (0.5 mol L − 1 ) for 30 min. Trehalose (Tre)-loaded DPMs required no further treatment, as Tre was uniformly distributed within graphene sheets via strong hydrogen bonding. The resulting samples are denoted as DPM n -X, where n denotes the applied mechanical compression strength (5–15 MPa), and X refers to the incorporated hydrophilic polymer (PAAm, Tre, SA, and PAMPS), respectively. This precise control over n and X enables the fine-tuning of interlayer nanostructures and chemical microenvironments in DPM n -X. Melting behavior of DPM n -X by DSC assessment The ice melting characteristics of fully hydrated samples were investigated by differential scanning calorimetry (DSC). After removing surface water, samples were completely sealed in aluminum crucibles, cooled to − 80°C at − 5°C min − 1 , held for 30 min, and subsequently heated to 40°C at 5°C min − 1 . All measurements were conducted under a constant nitrogen flow (50 mL min − 1 ). SDIE experiments The SDIE performance of DPM n -X was characterized using a custom-designed testing system illuminated by a xenon lamp light source (CEL-PE300L-3A) equipped with an AM 1.5 G optical filter to simulate standard solar irradiation (1 kW m − 2 ). Samples (20 mm × 20 mm) were subjected to continuous illumination until surface temperature stabilization. After the sample surface temperature reached a steady state, an electronic balance with a resolution of 0.1 µg was used to measure the difference in system mass loss before and after exposure to continuous sunlight for 1 h, thereby calculating the water evaporation rate. Water purification of complex wastewater The water purification performance of wastewater containing highly concentrated ions and strongly polar VOCs using optimized DPM 10 -PAMPS was evaluated using a custom-designed sealed device (effective area: 20 mm × 20 mm) under simulated solar illumination (CEL-PF300L-3A xenon lamp, AM 1.5G spectrum). Under solar irradiation, the increased interfacial temperature provides a strong driving force for the selective evaporation of water molecules. The water purification process employed a precisely controlled feed system. To evaluate performance across diverse hypersaline conditions, feed solutions included NaCl brines with salinities of 3.5 wt%, 10 wt%, and 20 wt%, as well as mixed heavy-metal brines (Cr 3+ , Pb 2+ , Zn 2+ , Ni 2+ , and Cu 2+ in an equal mass ratio of 1:1:1:1:1) with salinities of 5 wt%, 10 wt%, 15 wt%, and 20 wt%. For the treatment of water/VOCs solutions, the VOCs, including benzene, toluene, phenol, ethanol, isopropanol, or n-butanol, with different concentrations, were selected. The original solutions were continuously delivered to the device at a constant flow rate using a precision peristaltic pump. This configuration maintained a steady-state VOCs concentration throughout the experiments. The system incorporated an air circulation with generated water vapor being condensed in a − 20°C cold trap for subsequent analysis. The quantitative analysis of VOCs was performed using high-performance liquid chromatography (HPLC, Agilent G1322A) and gas chromatography (GC, Agilent 7890B), respectively. Standard curves were established for each VOC by correlating HPLC/GC peak areas with known concentrations, ensuring accurate quantification (R 2 > 0.990 for all analytes). Declarations Data availability The data generated in this study are provided in the Supplementary Information and Source Data file. Source data are provided with this paper. Acknowledgements P.Z. acknowledges Prof. L.Q. and Prof. Z.J. for the helpful advice and comments. This work was supported by the Hebei Provincial Natural Science Foundation, Excellent Youth Project (E2023202069), National Natural Science Foundation of China (22209036, U23A20119), and National Key R&D Program of China (2024YFF0506000, 2024YFB4609100). Author contributions P.Z., Z.J., and J.L. performed conceptualization. Q.J., J.B., and L.W. designed the research. 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ACS Appl Mater Interfaces 8:2097–2103 Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryInformation.docx Supplementary Information Tableofcontents.docx Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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08:06:53","extension":"html","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":134626,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8090933/v1/02a2d26c1077b56fea7c0456.html"},{"id":97418675,"identity":"0b4271bd-4445-4941-86cb-811941d1a1ba","added_by":"auto","created_at":"2025-12-04 08:06:53","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1348900,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eIllustration of DPM with confined water-selective highways for ultrafast purification of wastewater containing highly concentrated ions and strongly polar VOCs. \u003c/strong\u003eDPM’s interlayer nanostructures and chemical environments are precisely tailored by adjusting the mechanical compression strength and the types of hydrophilic polymer functional groups.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8090933/v1/b57c3a8099a7946d455548b7.png"},{"id":97666644,"identity":"6f350eba-bff1-40e6-acb2-d8cbf9a8a3ba","added_by":"auto","created_at":"2025-12-08 09:21:44","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1533011,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePreparation process and characterizations.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e Schematic illustration of the fabrication process of the DPM. \u003cstrong\u003eb\u003c/strong\u003e Photograph of a DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS sample before (left) and after (right) mechanical compression. SEM images of (\u003cstrong\u003ec\u003c/strong\u003e) PM\u003csub\u003e0\u003c/sub\u003e-PAMPS and (\u003cstrong\u003ed\u003c/strong\u003e) DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS at different magnifications. \u003cstrong\u003ee\u003c/strong\u003e FTIR of DPM\u003csub\u003e10\u003c/sub\u003e-PAAm, DPM\u003csub\u003e10\u003c/sub\u003e-Tre, DPM\u003csub\u003e10\u003c/sub\u003e-SA, and DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS, respectively. \u003cstrong\u003ef \u003c/strong\u003eEDS,\u003cstrong\u003e \u003c/strong\u003e(\u003cstrong\u003eg\u003c/strong\u003e) C1s, and (\u003cstrong\u003eh\u003c/strong\u003e) S2p XPS spectra of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8090933/v1/3d4a7db627ad3516c28a1c22.png"},{"id":97666559,"identity":"56415765-b576-4e62-9d37-b71b93ab32bd","added_by":"auto","created_at":"2025-12-08 09:21:33","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2204469,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eExploring confined water-selective highways in DPM\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e10\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e-X.\u003c/strong\u003e \u003cstrong\u003ea,b\u003c/strong\u003e Molecular models and corresponding binding energy of PAAm-water, Tre-water, SA-water, and PAMPS-water, respectively. \u003cstrong\u003ec\u003c/strong\u003e Saturated water content and (\u003cstrong\u003ed\u003c/strong\u003e) water contact angle of DPM\u003csub\u003e10\u003c/sub\u003e-X. \u003cstrong\u003ee\u003c/strong\u003e DSC curves of the melting behavior of water and water frozen in DPM\u003csub\u003e10\u003c/sub\u003e-X. \u003cstrong\u003ef\u003c/strong\u003e Raman spectra with fitting curves of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS. \u003cstrong\u003eg\u003c/strong\u003e DSC thermograms and (\u003cstrong\u003eh\u003c/strong\u003e) calculated evaporation enthalpy of water and water in DPM\u003csub\u003e10\u003c/sub\u003e-X. \u003cstrong\u003ei\u003c/strong\u003e A schematic diagram showing the confined water-selective highways in DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8090933/v1/4823e2faa3ba9525fd310020.png"},{"id":97666681,"identity":"654167b6-3ad0-49c0-a4a5-f52560b0828a","added_by":"auto","created_at":"2025-12-08 09:21:50","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1381967,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTreatment of various hypersaline solutions.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e Surface temperature of pure water and DPM\u003csub\u003e10\u003c/sub\u003e-X. \u003cstrong\u003eb\u003c/strong\u003e XRD spectra of DPM\u003csub\u003e10\u003c/sub\u003e-X. \u003cstrong\u003ec\u003c/strong\u003e Schematic diagram of DPM\u003csub\u003e10\u003c/sub\u003e-X for efficient salt resistance. \u003cstrong\u003ed\u003c/strong\u003e Water evaporation rate of pure water and DPM\u003csub\u003e10\u003c/sub\u003e-X under 1 kW m\u003csup\u003e−2\u003c/sup\u003e. \u003cstrong\u003ee\u003c/strong\u003e Water evaporation rates of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS in different saline solutions. \u003cstrong\u003ef\u003c/strong\u003e Water evaporation rates of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS in hypersaline solutions containing different heavy metal ions. \u003cstrong\u003eg\u003c/strong\u003e Long-term water evaporation rate of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS in a high-salinity solution (20 wt% NaCl) under 1 kW m\u003csup\u003e−2\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8090933/v1/1c0a556c04d6bc76d032936a.png"},{"id":97666425,"identity":"fd152909-37e4-4504-9dec-de5317ce1e77","added_by":"auto","created_at":"2025-12-08 09:21:10","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2080066,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDevice design and mechanism investigation. a\u003c/strong\u003e Schematic diagrams and photographs of a custom-designed sealed device to purify water/VOCs solutions. \u003cstrong\u003eb,c\u003c/strong\u003e Molecular models and corresponding binding energy of PAMPS-benzene, PAMPS-toluene, PAMPS-phenol, PAMPS- n-butanol, PAMPS-isopropanol, and PAMPS-ethanol, respectively. \u003cstrong\u003ed\u003c/strong\u003e MD simulation snapshots of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS models for purifying water/ethanol at 0, 10, 30, and 50 ns. Graphene, PAMPS, water, ethanol, and Na\u003csup\u003e+\u003c/sup\u003e are in green, orange, cyan, magenta, and purple, respectively.\u003cstrong\u003e e\u003c/strong\u003e MSD curves of water and ethanol molecules over time in the MD simulations for water/ethanol treatment based on DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS. \u003cstrong\u003ef\u003c/strong\u003e Density profiles of water and ethanol at different positions in the MD simulations for water/ethanol separation using DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8090933/v1/249d3a6a50db332f521f74e3.png"},{"id":97418682,"identity":"c3e08ed3-c54d-485f-a72a-61d2369f9f3d","added_by":"auto","created_at":"2025-12-04 08:06:53","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1553907,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEliminating both common and strongly polar VOCs using DPM\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e10\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e-PAMPS.\u003c/strong\u003e \u003cstrong\u003ea−c\u003c/strong\u003e Removal rate of benzene, toluene, and phenol from water/aromatic VOCs using DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS under 1 kW m\u003csup\u003e−2\u003c/sup\u003e. \u003cstrong\u003ed−f\u003c/strong\u003e Separation factors of water/ethanol, water/isopropanol, and water/n-butanol separation. \u003cstrong\u003eg−i\u003c/strong\u003e Separation performance of water/alcoholic VOCs compared with other state-of-the-art membranes previously reported.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8090933/v1/6d9e0521f49426818eea8bb8.png"},{"id":97418683,"identity":"2527c76b-172f-4ef8-a0eb-2d06cd799168","added_by":"auto","created_at":"2025-12-04 08:06:53","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":2271954,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOutdoor scaled-up performance validation using DPM\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e10\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e-PAMPS.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e Photographs of a designed large-scale device (0.4 m × 0.4 m) for treating complex wastewater in outdoor environments. The lower layer with microfluidic channels ensures a sufficient and appropriate water supply, and the upper layer utilizes air circulation to facilitate clean vapor collection. \u003cstrong\u003eb \u003c/strong\u003eAmbient temperature and outdoor solar intensity from 9:00 to 17:00 on November 2, 2025, in Tianjin. \u003cstrong\u003ec,d\u003c/strong\u003e The corresponding surface temperature and evaporation rate of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS. \u003cstrong\u003ee\u003c/strong\u003e Photographs of the complex wastewater containing various salts and VOCs before and after purification. \u003cstrong\u003ef\u003c/strong\u003e Concentrations and removal efficiencies of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS before and after purifying the complex wastewater.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-8090933/v1/88f10cc1b72e52f3deb0fc3b.png"},{"id":97677607,"identity":"7ad1954d-dcb0-4947-ab35-6182c2456e88","added_by":"auto","created_at":"2025-12-08 09:53:42","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":13418289,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8090933/v1/505d5491-7afe-4448-b5db-3bfd93bf47d8.pdf"},{"id":97666240,"identity":"47477e13-4b13-4331-97cb-17bb401f6462","added_by":"auto","created_at":"2025-12-08 09:20:42","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":11627934,"visible":true,"origin":"","legend":"Supplementary Information","description":"","filename":"SupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-8090933/v1/0267d6b2b4b9f82802c31053.docx"},{"id":97668112,"identity":"26362df7-43da-41f4-a510-7e2368c41a1d","added_by":"auto","created_at":"2025-12-08 09:24:51","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":325166,"visible":true,"origin":"","legend":"","description":"","filename":"Tableofcontents.docx","url":"https://assets-eu.researchsquare.com/files/rs-8090933/v1/5c1990ec40e5e5477202dd25.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Confined water-selective highways in a densified photothermal membrane enable ultrafast purification of complex wastewater","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSevere water scarcity is a mounting global challenge that demands sustainable water purification technologies\u003csup\u003e\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. Solar-driven interfacial evaporation (SDIE) offers a clean and energy-efficient strategy for producing clean water\u003csup\u003e\u003cspan additionalcitationids=\"CR5 CR6\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. Recent advances have led to the development of diverse photothermal materials capable of treating complex wastewater\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. In particular, the application of SDIE systems to treat complex wastewater with high salinity and strong polarity, primarily originating from key industries such as petrochemical, pharmaceutical, and electronics manufacturing, has become a current research focus\u003csup\u003e\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. However, photothermal materials specifically designed for these challenging wastewaters remain scarce, as simultaneously achieving a high water evaporation rate, excellent removal efficiency, and long-term stability is highly demanding\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eOn one hand, in the SDIE system, addressing highly saline wastewater usually involves non-volatile contaminants, such as various salt ions. These substances remain in the residual water and do not evaporate with water molecules\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. During evaporation, these non-volatile contaminants tend to crystallize and accumulate on the photothermal materials, potentially degrading performance over time. Strategies including convective/diffusive reflow, non-contact configurations, and ionic diffusion equilibrium have been explored to mitigate salt accumulation during SDIE\u003csup\u003e\u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. While partially effective, these approaches often incur substantial heat losses, block water transport pathways, and suffer from electrostatic shielding effects, ultimately limiting the water evaporation rate\u003csup\u003e\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Thus, efficient and sustainable solutions to salt buildup in SDIE remain urgently needed for treating hypersaline wastewater.\u003c/p\u003e\u003cp\u003eOn the other hand, removal of volatile organic compounds (VOCs) such as toluene, phenol, and trichloroethylene from wastewater has been investigated via air stripping\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e, adsorption\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e, photocatalytic degradation\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e,\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e, pervaporation\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e, and membrane sieving\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e,\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. Among these, membrane-based photothermal materials offer notable advantages, including enhanced removal efficiency, operational simplicity, and independence from added chemicals or catalysts\u003csup\u003e\u003cspan additionalcitationids=\"CR34\" citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. However, these photothermal materials typically exhibit a low water evaporation rate of no more than 1.53 kg m\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e h\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e under 1 kW m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e and limited efficacy at VOC concentrations exceeding 400 mg L\u003csup\u003e\u0026ndash;\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Furthermore, few studies have addressed the treatment of strongly polar VOCs, including ethanol, isopropanol, and n-butanol, particularly those originating from the electronics and semiconductor manufacturing industries. Collectively, these challenges highlight the pressing need to precisely engineer the interfacial nanostructure and surface chemistry of photothermal materials for efficient treatment of complex wastewater containing highly concentrated ions and strongly polar VOCs.\u003c/p\u003e\u003cp\u003eNotably, VOCs removal in membrane-based photothermal materials primarily relies on molecular sieving effects governed by nanopore size and surface functional group affinity\u003csup\u003e\u003cspan additionalcitationids=\"CR37\" citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. Strong intermolecular interactions between water and VOCs, particularly strongly polar species such as ethanol, isopropanol, and n-butanol, pose significant challenges for separation processes. Even at trace levels, these substances still present serious risks to ecosystems and human health\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e,\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e. Consequently, the design of next-generation photothermal materials capable of simultaneously achieving rapid water evaporation and selective removal of highly saline and polar VOCs wastewater represents a critical frontier in water purification technologies.\u003c/p\u003e\u003cp\u003eThe overall heat transfer and water evaporation performance of the SDIE system is largely governed by the thickness and area of the evaporative thin-film region. Photothermal interfaces engineered with \u0026ldquo;nanostructure confinement\u0026rdquo; and \u0026ldquo;surface confinement\u0026rdquo; architectures offer precise control over water transport, evaporation energy input, and phase-change dynamics\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e,\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. For instance, nanoscale channels can significantly expand the solid-liquid interfacial area, where interfacial interactions profoundly influence liquid behavior under confinement. The evaporation energy required at the solid-liquid interface within nanostructures is markedly lower than that at the liquid-vapor interface center, thereby enhancing evaporation within nanoporous domains\u003csup\u003e\u003cspan additionalcitationids=\"CR44\" citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e. Moreover, the nanopore size and surface functional group affinity of photothermal interfaces define selective water transport pathways, enabling efficient exclusion of salt ions and strongly polar VOCs through synergistic effects of size sieving and strong hydration interactions\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. As such, achieving efficient water/ions and water/VOCs separation while maintaining a high water evaporation rate requires photothermal membrane interlayer nanostructures and chemical environments engineered with molecular precision.\u003c/p\u003e\u003cp\u003eHere, a densified photothermal membrane (DPM) with confined water-selective highways is reported for ultrafast and efficient purification of wastewater containing highly concentrated ions and strongly polar VOCs. Through mechanical compression of graphene architecture and strategic selection of hydrophilic polymers, the DPM\u0026rsquo;s interlayer nanostructures and chemical environments are tailored with molecular precision. This architecture promotes selective water transport while effectively rejecting a broad spectrum of highly concentrated ions and strongly polar VOCs due to the synergistic effect of steric hindrance and chemical selectivity. The design of the DPM is guided by three key principles: (1) utilizing mechanical compression to regulate the densification of the graphene framework, thereby better balancing water mass transfer, heat loss, and evaporation rate; (2) rationally selecting hydrophilic polymers that form strong interactions with water molecules, establishing confined water-selective highways; and (3) coordinating the size-sieving effects of graphene interlayer nanostructures and the stable hydration layers formed by hydrophilic polymers, to achieve efficient removal of highly concentrated ions and strongly polar VOCs (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Under 1 kW m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e illumination, DPM achieves a high water evaporation rate of up to 2.58 kg m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Simultaneously, the DPM exhibits stable operation for more than 200 h in diverse near-saturated hypersaline solutions (20 wt% salinity), while enabling the clean water production from both common (e.g., benzene, toluene, phenol, rejection rate ˃99.99%) and strongly polar VOCs (e.g., ethanol, isopropanol, n-butanol, rejection rate ˃99.0%) at high concentrations. These findings demonstrate the critical importance of molecular-level interfacial engineering in advancing high-performance SDIE for complex wastewater purification.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003ePreparation and characterization\u003c/h2\u003e\u003cp\u003eTo fabricate the DPM, a mixture of graphene oxide (GO) and hydrophilic polymers was horizontal directional freeze-dried to obtain a three-dimensional framework, which was then subjected to mechanical compression, thermal annealing, and chemical crosslinking (Fig.\u0026nbsp;2a). We employ tunable mechanical compression (5\u0026ndash;15 MPa, 2 min) and a series of hydrophilic polymers bearing distinct functional groups, including amide (acrylamide) (AAm), hydroxyl (trehalose) (Tre), carboxyl (sodium alginate) (SA), and sulfonate (2-acrylamido-2-methylpropane sulfonic acid sodium salt) (AMPS), to precisely tailor the interlayer nanostructures and chemical environments of DPM. The resulting samples are denoted as DPM\u003csub\u003en\u003c/sub\u003e-X, where n represents the applied mechanical compression strength (5\u0026ndash;15 MPa), and X denotes the incorporated hydrophilic polymer (PAAm, Tre, SA, and PAMPS), respectively. Upon mechanical compression, the thickness of the 3D graphene foam is significantly reduced, transforming into a densified membrane structure (Fig.\u0026nbsp;2b and Supplementary Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). As a representative example, scanning electron microscope (SEM) images reveal that the interlayer nanostructures of DPM\u003csub\u003en\u003c/sub\u003e-PAMPS gradually shrink with increasing mechanical compression strength, exhibiting a more compact architecture. However, all DPM\u003csub\u003en\u003c/sub\u003e-PAMPS remain less compact than the vacuum-filtrated counterpart (DPM\u003csub\u003eF\u003c/sub\u003e-PAMPS) (Supplementary Fig. S2). The degree of interlayer densification plays a critical role in regulating water transport, thermal losses, and water evaporation performance\u003csup\u003e\u003cspan additionalcitationids=\"CR47\" citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e. In the case of DPM\u003csub\u003e5\u003c/sub\u003e-PAMPS, the loosely packed structure permits excessive water flow and heat dissipation, thereby reducing the water evaporation rate. Conversely, DPM\u003csub\u003e15\u003c/sub\u003e-PAMPS and DPM\u003csub\u003eF\u003c/sub\u003e-PAMPS show overly compacted \u003c/p\u003e\u003cp\u003e\u003cb\u003eFigure\u0026nbsp;2 | Preparation process and characterizations. a\u003c/b\u003e Schematic illustration of the fabrication process of the DPM. \u003cb\u003eb\u003c/b\u003e Photograph of a DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS sample before (left) and after (right) mechanical compression. SEM images of (\u003cb\u003ec\u003c/b\u003e) PM\u003csub\u003e0\u003c/sub\u003e-PAMPS and (\u003cb\u003ed\u003c/b\u003e) DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS at different magnifications. \u003cb\u003ee\u003c/b\u003e FTIR of DPM\u003csub\u003e10\u003c/sub\u003e-PAAm, DPM\u003csub\u003e10\u003c/sub\u003e-Tre, DPM\u003csub\u003e10\u003c/sub\u003e-SA, and DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS, respectively. \u003cb\u003ef\u003c/b\u003e EDS, (\u003cb\u003eg\u003c/b\u003e) C1s, and (\u003cb\u003eh\u003c/b\u003e) S2p XPS spectra of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS.\u003c/p\u003e\u003cp\u003earchitectures that restrict water transport, also resulting in reduced water evaporation rate. Notably, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS achieves an optimal balance, enabling adequate water transport, minimal heat losses, and a high evaporation rate (Supplementary Fig. S3, 10 MPa is the optimal mechanical compressive strength). This DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS can be fabricated over a large area and appears visibly black, contributing to excellent light absorption (Supplementary Fig. S4).\u003c/p\u003e\u003cp\u003eSEM images confirm that DPM\u003csub\u003e10\u003c/sub\u003e-PAAm, DPM\u003csub\u003e10\u003c/sub\u003e-Tre, DPM\u003csub\u003e10\u003c/sub\u003e-SA, and DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS all exhibit significantly densified interlayer nanostructures, in contrast to the non-compressed composites (PM\u003csub\u003e0\u003c/sub\u003e-PAMPS), which display loose frameworks (Fig.\u0026nbsp;2c,d and Supplementary Fig. S5). Fourier-transform infrared spectroscopy (FTIR) analysis reveals distinct peaks for DPM\u003csub\u003e10\u003c/sub\u003e-\u003c/p\u003e\u003cp\u003ePAAm at 3360, 1660, and 1420 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, corresponding to N\u0026ndash;H stretching, C\u0026thinsp;=\u0026thinsp;O stretching, and C\u0026ndash;N stretching vibrations, respectively, confirming the presence of \u0026ndash;CONH\u003csub\u003e2\u003c/sub\u003e groups (Fig.\u0026nbsp;2e)\u003csup\u003e\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e. For DPM\u003csub\u003e10\u003c/sub\u003e-Tre, a broad band at 3200\u0026ndash;3600 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and a peak at 1030 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are assigned to O\u0026ndash;H and C\u0026ndash;O\u0026ndash;C stretching vibrations, indicating successful \u0026ndash;OH modification. DPM\u003csub\u003e10\u003c/sub\u003e-SA exhibits characteristic \u0026ndash;COO⁻ asymmetric and symmetric stretching vibrations at 1600 and 1410 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, along with a C\u0026ndash;O\u0026ndash;C stretching vibration at 1030 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, verifying the incorporation of \u0026ndash;COO⁻\u003csup\u003e35\u003c/sup\u003e. DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS exhibits three strong absorption peaks at 1350, 1200, and 1050 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, representing the characteristic peaks of the sulfonate, confirming the loading of \u0026ndash;SO\u003csub\u003e3\u003c/sub\u003e⁻ groups\u003csup\u003e\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e. These results are further supported by energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), which confirm the successful functionalization of hydrophilic groups \u0026ndash;CONH\u003csub\u003e2\u003c/sub\u003e, \u0026ndash;OH, \u0026ndash;COO⁻, and \u0026ndash;SO\u003csub\u003e3\u003c/sub\u003e⁻ in DPM\u003csub\u003e10\u003c/sub\u003e-PAAm, DPM\u003csub\u003e10\u003c/sub\u003e-Tre, DPM\u003csub\u003e10\u003c/sub\u003e-SA, and DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS, respectively (Fig.\u0026nbsp;2f\u0026ndash;h, and Supplementary Figs. S6\u0026ndash;9).\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eConfined water-selective highways in DPM-X\u003c/h3\u003e\n\u003cp\u003eThe interlayer nanostructures and chemical environments regulation of DPM\u003csub\u003e10\u003c/sub\u003e-X with molecular precision can form the confined water-selective highways. By coupling the size-sieving effect of graphene interlayers with strong water interaction derived from hydrophilic polymers, the DPM\u003csub\u003e10\u003c/sub\u003e-X achieves ultrafast purification of wastewater containing high salinity and polar VOCs. Among them, the interlayer hydrophilic functional groups of the DPM\u003csub\u003e10\u003c/sub\u003e-X play a pivotal role in mediating interactions with water molecules. The interactions between water molecules and DPM\u003csub\u003e10\u003c/sub\u003e-PAAm or DPM\u003csub\u003e10\u003c/sub\u003e-Tre are primarily governed by hydrogen bonding, with the abundant \u0026ndash;OH groups in DPM\u003csub\u003e10\u003c/sub\u003e-Tre exhibiting stronger binding affinity toward water. In contrast, DPM\u003csub\u003e10\u003c/sub\u003e-SA and DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS engage in both hydrogen bonding and ion-dipole interactions with water molecules, leading to further enhanced water affinity. Notably, the strong ion-dipole interactions between \u0026ndash;SO\u003csub\u003e3\u003c/sub\u003e⁻ groups in DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS and water have higher bond strength and lower directionality, resulting in higher affinity for water molecules. Electrostatic potential mapping reveals that PAMPS molecules, characterized by their high density of \u0026ndash;SO\u003csub\u003e3\u003c/sub\u003e⁻ groups, provide abundant binding sites for water molecules, enabling preferential water transport (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ea and Supplementary Fig. S10)\u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e. Consistently, density functional theory (DFT) calculations show that PAMPS-water exhibits the highest binding energy (84.78 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), significantly exceeding those of SA-water (75.35 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), Tre-water (61.46 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), and PAAm-water (49.37 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). These results confirm the strongest water affinity of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS, which is favorable for constructing confined water-selective highways within the graphene interlayer nanostructures for ultrafast purification of wastewater containing highly concentrated ions and strongly polar VOCs.\u003c/p\u003e\u003cp\u003eAdditionally, the hydrophilic functional groups at the photothermal interface can regulate the water states within the DPM\u003csub\u003e10\u003c/sub\u003e-X, thereby influencing water transport behavior and evaporation rate\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. Among all samples, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS exhibits the highest saturated water content (0.73 g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), yet it remains significantly lower than that of conventional hydrogels, indicating its strongest affinity toward water molecules (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). It also exhibits the lowest water contact angle (44.7\u0026deg;), suggesting enhanced water transport performance compared to the other samples (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). Differential scanning calorimetry (DSC) measurements of melting enthalpy reveal that, compared to pure water, the onset melting points of DPM\u003csub\u003e10\u003c/sub\u003e-PAAm, DPM\u003csub\u003e10\u003c/sub\u003e-Tre, DPM\u003csub\u003e10\u003c/sub\u003e-SA, and DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS all shift below 0\u0026deg;C, indicating the coexistence of freezable and non-freezable water within the materials (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ee). Among them, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eexhibits the highest melting enthalpy, likely due to a greater proportion of intermediate water (IW) arising from its stronger affinity toward water molecules. This was further supported by Raman spectroscopy, where DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS displays the highest IW/FW ratio (0.164), suggesting enhanced interaction with water that promotes the formation of IW (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ef and Supplementary Fig. S11). The increased IW content facilitates water activation and lowers the\u003c/p\u003e\u003cp\u003eenergy required for evaporation. As a result, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS achieves remarkably low water evaporation enthalpy of 1224.30 J g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, significantly lower than that of pure water (2440.0 J g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), as well as DPM\u003csub\u003e10\u003c/sub\u003e-PAAm (1875.07 J g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), DPM\u003csub\u003e10\u003c/sub\u003e-Tre (1372.82 J g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), and DPM\u003csub\u003e10\u003c/sub\u003e-SA (1329.63 J g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003eg,h).\u003c/p\u003e\u003cp\u003eConsequently, the abundant \u0026ndash;SO\u003csub\u003e3\u003c/sub\u003e⁻ in DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS enables strong ion-dipole and hydrogen-bonding interactions with water molecules, offering abundant binding sites and facilitating the formation of confined water-selective highways. The confined water transport in DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS is primarily governed by strong interactions between hydrophilic polymers and water molecules. Specifically, the ion-dipole interactions between \u0026ndash;SO\u003csub\u003e3\u003c/sub\u003e⁻ and water are stronger than the hydrogen bonding among water molecules, leading to preferential transport of water into DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS and its association with hydrophilic polymer chains. Under sunlight, the bound water is subsequently transported toward the evaporation interface via hydrogen-bond networks (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ei). Therefore, benefiting from the graphene interlayer nanostructures and precisely regulated chemical environments, the confined water-selective highways in DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS not only enable ultrafast water transport, but also achieve effective removal of highly concentrated ions and strongly polar VOCs based on size-sieving and strong hydration effects.\u003c/p\u003e\n\u003ch3\u003eSDIE performance and treatment of hypersaline solutions\u003c/h3\u003e\n\u003cp\u003eBenefiting from the excellent light-harvesting property of graphene, DPM\u003csub\u003e10\u003c/sub\u003e-X exhibits strong broadband solar absorption across the full solar spectrum (250\u0026ndash;2500 nm). Under 1kW m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, the surface temperatures of DPM\u003csub\u003e10\u003c/sub\u003e-PAAm, DPM\u003csub\u003e10\u003c/sub\u003e-Tre, DPM\u003csub\u003e10\u003c/sub\u003e-SA, and DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS rapidly increase within 5 min and stabilize at 51.5\u0026ndash;52.5\u0026deg;C, indicating efficient photothermal conversion performance (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). Through mechanical compression combined with chemical modification using hydrophilic polymers, the graphene interlayer nanostructures are precisely tuned. According to X-ray diffraction (XRD) analysis, the interlayer spacing of DPM\u003csub\u003e10\u003c/sub\u003e-X is maintained in the narrow range of 6.31\u0026ndash;6.41 \u0026Aring; (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). This interlayer spacing is sufficiently small to effectively exclude hydrated salt ions such as Na⁺ (hydrated radius 3.58 \u0026Aring;) and Cl⁻ (3.32 \u0026Aring;), while permitting efficient water molecule transport, thereby endowing the material with excellent salt-rejection capabilities (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003ec).\u003c/p\u003e\u003cp\u003eUnder 1 kW m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS achieves a maximum water evaporation rate of 2.58 kg m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in pure water (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003ed). Based on this superior performance, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS is further selected for SDIE tests under varying salinities, including pure water and saline solutions with 3.5 wt%, 10 wt%, and 20 wt% NaCl. Although the water evaporation rate decreases with increasing salt concentration, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS still maintains a high evaporation rate of 1.50 kg m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e even in near-saturated 20 wt% NaCl, significantly outperforming the evaporation rate of pure water under the same conditions (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003ee). Meanwhile, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS is also applicable for treating complex saline solutions containing various heavy metal ions. In hypersaline solutions with salinities of 5 wt%, 10 wt%, 15 wt%, and 20 wt%, where Cr\u003csup\u003e3+\u003c/sup\u003e, Pb\u003csup\u003e2+\u003c/sup\u003e, Zn\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, and Cu\u003csup\u003e2+\u003c/sup\u003e are present in an equal mass ratio of 1:1:1:1:1. The corresponding water evaporation rates reach 2.13, 1.99, 1.81, and 1.76 kg m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003ef). Notably, the water evaporation rates in these multicomponent heavy metal solutions are slightly higher than those observed in NaCl solutions of equivalent salinity. This enhancement is likely due to the\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003estrong hydration interactions between Na⁺/Cl⁻ ions and water molecules, which significantly reduce the fraction of free water available for evaporation. In contrast, mixed heavy metal ions such as Cr\u003csup\u003e3+\u003c/sup\u003e, Pb\u003csup\u003e2+\u003c/sup\u003e, Zn\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, and Cu\u003csup\u003e2+\u003c/sup\u003e exhibit diverse hydration capabilities and compete for coordination with water molecules. Such ion-ion and ion-solvent interactions disrupt the ordered hydration structures, leading to a reduced overall hydration degree and an increased proportion of free water, thereby facilitating faster evaporation. To evaluate its long-term operational stability in highly saline environments, continuous water evaporation tests were performed under 1 kW m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, with 8 h operation cycles. Remarkably, after 200 h of ongoing testing, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS retains a steady water evaporation rate of 1.50 kg m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, demonstrating excellent salt resistance and operational durability (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003eg).\u003c/p\u003e\n\u003ch3\u003ePurifying both common and strongly polar VOCs\u003c/h3\u003e\n\u003cp\u003eVOCs, many of which are highly toxic, are widely present throughout the water cycle. However, their complex physicochemical properties make their separation from water extremely challenging\u003csup\u003e\u003cspan additionalcitationids=\"CR52\" citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e. While certain aromatic VOCs exhibit low aqueous solubility, their inherent volatility allows them to persist in trace amounts, posing serious risks to both human health and the environment. In contrast, most phenolic and alcoholic VOCs possess strong hydrophilicity. Their polarity, which closely resembles that of water, along with the formation of azeotropes, renders conventional separation methods ineffective\u003csup\u003e\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e,\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e. By precisely tuning the graphene interlayer nanostructures and chemical environments of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS, confined water-selective highways have been established, demonstrating promising potential for the efficient separation of water/VOCs mixtures. The optimized DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS was integrated into a custom-designed sealed device to purify aqueous solutions containing VOCs. In this setup, the water/VOCs solution was introduced from the bottom chamber, while the top chamber was connected to a condenser-cooled vessel to collect the generated water vapor. The effective water evaporation area of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS was 20 mm \u0026times; 20 mm (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003ea and Supplementary Fig. S12). Under solar irradiation, the elevated interfacial temperature provides a strong driving force for the selective evaporation of water molecules.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTwo representative classes of VOCs were selected for evaluation, including common aromatic VOCs (benzene, toluene, phenol) and strongly polar alcoholic VOCs (ethanol, isopropanol, and n-butanol). The purification performance of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS in the water/VOCs system is closely associated with both the molecular size of the VOCs and their intermolecular interactions with water. Compared with hydrated ions, VOC molecules are significantly larger in size, enabling preliminary size-based exclusion via the compact interlayer nanostructures of graphene constructed through mechanical compression. However, the separation becomes increasingly challenging for VOCs exhibiting stronger interactions with water molecules. The intermolecular interactions of water-VOCs generally follow the order of benzene\u0026thinsp;\u0026lt;\u0026thinsp;toluene\u0026thinsp;\u0026lt;\u0026thinsp;phenol\u0026thinsp;\u0026lt;\u0026thinsp;n-butanol\u0026thinsp;\u0026lt;\u0026thinsp;isopropanol\u0026thinsp;\u0026lt;\u0026thinsp;ethanol\u0026thinsp;\u0026lt;\u0026thinsp;water. Alcoholic VOCs, in particular, exhibit strong hydrogen bonding and form azeotropes with water, further complicating their separation. DFT calculations reveal that the interaction energy of PAMPS-water molecules is substantially stronger than that with VOCs molecules, including benzene, toluene, phenol, n-butanol, isopropanol, and ethanol (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003eb,c, and Supplementary Fig. S13).\u003c/p\u003e\u003cp\u003eTo gain a deeper understanding of the underlying mechanism, MD simulations were conducted to investigate the molecular diffusion behavior in the model based on DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS (Supplementary Fig. S14). Given the strongest intermolecular interactions between water and ethanol, we selected their mixture as a representative strongly polar VOC system for the MD simulations. The results show that DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS displays preferential water transport while effectively excluding ethanol (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003ed and Supplementary Fig. S15). No ethanol molecules are observed in the snapshot, demonstrating the excellent elimination performance of ethanol from water using DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS. The mean square displacement (MSD) curve over time reveals that, compared with ethanol, water exhibits superior diffusion behavior in DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003ee and Supplementary Fig. S16). Simultaneously, the density profiles of water and ethanol at different positions demonstrate that only water molecules selectively transport across the DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS, whereas ethanol molecules are effectively retained (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003ef and\u003c/p\u003e\u003cp\u003eSupplementary Fig. S17), demonstrating the excellent performance of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS in purifying water/ethanol mixtures. These MD simulations confirm that precise regulation of the interlayer nanostructures and chemical environments in DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS facilitates selective water transport while efficiently rejecting a wide range of strongly polar VOCs, owing to the synergistic effects of steric hindrance and chemical selectivity\u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e,\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eWe evaluated the separation performance of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS in water/aromatic VOCs (benzene, toluene, and phenol) with varying VOC concentrations (100, 300, 500, and 1000 ppm). Across all tested concentrations, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS exhibits a high water evaporation rate along with excellent VOCs removal efficiencies as high as 99.99% (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003ea\u0026thinsp;\u0026minus;\u0026thinsp;c, standard curves of aromatic VOCs are shown in Supplementary Fig. S18). Whether the high carcinogenic benzene or irritants like toluene and phenol, the VOC concentrations in generated water vapor are all below the health-drinking water criteria recommended by the World Health Organization (WHO) and U.S. Environmental Protection Agency (US-EPA) (Supplementary Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Notably, even at a high concentration of 1000 ppm (e.g., phenol), the rejection efficiency reaches up to 99.99%, significantly outperforming previously reported photothermal membranes for VOCs removal (Supplementary Table S2)\u003csup\u003e\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e,\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e\u003c/sup\u003e. Even in complex VOC systems where benzene, toluene, and phenol are present simultaneously, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS also demonstrated excellent elimination efficiency across all tested concentrations, achieving consistent removal of residual benzene (0.001\u0026ndash;0.004 ppm), toluene (0.017\u0026ndash;0.027 ppm), and phenol (0.01\u0026ndash;0.05 ppm) in these multicomponent solutions (Supplementary Fig. S19). Additionally, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS was tested in water/alcoholic VOCs, comprising strongly polar\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003especies, including ethanol, isopropanol, and n-butanol (standard curves of alcoholic VOCs are shown in Supplementary Fig. S20). These mixtures contain alcoholic VOCs mass fractions ranging from 30 to 90 wt%. Despite the high alcoholic VOCs content, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS achieves a high water evaporation rate and the resultant water content ranging from 99.50 wt% to 99.72 wt% for all tested alcoholic VOCs (rejection rate ˃99.0%), demonstrating its outstanding separation capability (Supplementary Fig. S21).\u003c/p\u003e\u003cp\u003eThe separation performance of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS is evaluated using the separation factor (\u003cem\u003eα\u003c/em\u003e), as defined by the following equations\u003csup\u003e\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e\u003c/sup\u003e:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\begin{array}{c}\\text{\u0026alpha;}\\text{=}\\frac{{\\text{P}}_{\\text{W}}/{\\text{P}}_{\\text{E}}}{{\\text{F}}_{\\text{W}}/{\\text{F}}_{\\text{E}}}\\#\\text{(}\\text{1}\\text{)}\\end{array}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eHere, \u003cem\u003eP\u003c/em\u003e\u003csub\u003eW\u003c/sub\u003e and \u003cem\u003eP\u003c/em\u003e\u003csub\u003eE\u003c/sub\u003e denote the mass fractions of water and alcoholic VOCs in the collected water, while \u003cem\u003eF\u003c/em\u003e\u003csub\u003eW\u003c/sub\u003e and \u003cem\u003eF\u003c/em\u003e\u003csub\u003eE\u003c/sub\u003e represent the corresponding mass fractions in the feed solution. Based on these calculations, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS achieves separation factors as high as 2638, 2186, and 2299 for water/ethanol, water/isopropanol, and water/n-butanol mixtures, respectively (with an initial water/alcoholic VOCs mass ratio of 1:9) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003ed\u0026thinsp;\u0026minus;\u0026thinsp;f), demonstrating superior performance over previously reported membranes in alcoholic VOCs separation (Supplementary Tables S3\u0026thinsp;\u0026minus;\u0026thinsp;5). Furthermore, in the complex water/alcoholic VOCs solutions with 30 wt%, 60 wt%, and 90 wt% (where ethanol, isopropanol, and n-butanol are present in an equal mass ratio of 1:1:1), the resultant water content reaches more than 99.52%, demonstrating the outstanding separation performance of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS (Supplementary Fig. S22). Compared with other state-of-the-art membranes previously reported for water/alcoholic VOCs separations, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS exhibits a remarkable advantage in the selective removal of alcoholic VOCs (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003eg\u0026ndash;i and Supplementary Figs. S23\u0026ndash;25).\u003c/p\u003e\n\u003ch3\u003eOutdoor scaled-up performance evaluation\u003c/h3\u003e\n\u003cp\u003eTo evaluate the practical applicability of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS for treating highly challenging complex wastewater, we designed and scaled up a device for validation under outdoor conditions (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003ea). The scaled-up device is constructed from polytetrafluoroethylene with dimensions of 0.4 m \u0026times; 0.4 m (effective evaporation area of 0.04 m\u003csup\u003e2\u003c/sup\u003e). The lower water supply layer incorporates microchannels to ensure adequate water delivery. Circulating air was introduced into the upper layer to efficiently transport clean water vapor to the collection bottles\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eplaced in the condensate, while preventing condensation on the glass of the light-transmitting layer. This approach avoids reduced light absorption and low water evaporation rates. The complex wastewater feed contained mixed salt ions as well as aromatic and alcoholic VOCs, including Na\u003csup\u003e+\u003c/sup\u003e (50,000 ppm), Cu\u003csup\u003e2+\u003c/sup\u003e (50,000 ppm), toluene (500 ppm), phenol (1000 ppm), ethanol (50,000 ppm), and n-butanol (50,000 ppm). Throughout the outdoor tests, ambient temperature, solar intensity, surface temperature, and evaporation rates were monitored in real time from 9:00 to 17:00, November 2, 2025 (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003eb,c). DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS shows a higher surface temperature compared to complex wastewater. It also exhibits a favorable water evaporation rate under low solar intensity and ambient outdoor temperatures (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003ed). Benefiting from the synergistic effect of steric hindrance and chemical selectivity, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS promotes selective water transport while effectively rejecting a broad spectrum of highly concentrated ions and strongly polar VOCs (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003ee). Under low solar irradiance and ambient winter temperatures, the DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS-based device achieves an outdoor clean water collection output of 5.75 kg m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e day\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e from a complex wastewater system. Meanwhile, DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS exhibits excellent removal efficiencies for various contaminants, reaching 99.99% (Na\u003csup\u003e+\u003c/sup\u003e), 99.99% (Cu\u003csup\u003e2+\u003c/sup\u003e), 99.97% (toluene), 99.99% (phenol), 99.40% (ethanol), and 99.36% (n-butanol), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003ef). This work highlights the potential of DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS for scalable and robust SDIE applications in challenging real-world conditions.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eWe report a DPM with confined water-selective highways that enables ultrafast purification of wastewater containing highly concentrated ions and strongly polar VOCs. Through the synergistic design of mechanical compression and hydrophilic polymer selection, DPM offers confined water-selective highways that facilitate rapid and selective water transport while effectively excluding both highly concentrated ions and strongly polar VOCs. The DPM demonstrates a high water evaporation rate of up to 2.58 kg m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e under 1 kW m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. DPM maintains stable performance for over 200 h in various near-saturated hypersaline solutions (20 wt% salinity) and enables the production of clean water from both common and strongly polar VOCs, even at very high concentrations. Integration of DPM with the device validates the scaling-up feasibility of this approach for treating complex wastewater. These findings highlight the potential of nanoscale structural confinement and chemical microenvironment tuning in advancing SDIE-based technologies toward practical, high-performance water purification, particularly under conditions involving hypersaline and VOC-laden wastewater.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003ePreparation of DPM\u003csub\u003en\u003c/sub\u003e-X\u003c/h2\u003e\u003cp\u003eGraphene oxide (GO) was synthesized via a modified Hummers method. To prepare the mixed dispersion, a hydrophilic polymer solution (5 wt%) was introduced into the GO suspension (7.0 mg mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) at a volume ratio of 1:9, followed by thorough homogenization under ultrasonication. A certain amount of ethanol was added to the mixed solution to reduce the surface tension and regulate the oriented ice crystal growth rate. The resulting dispersion was rapidly pre-frozen horizontally in liquid nitrogen and subsequently freeze-dried (BIOCOOL, FD-1A-50+) to sublimate the ice under low temperature and pressure, yielding three-dimensional (3D) GO/hydrophilic polymer aerogels with interconnected porous architectures. The as-prepared aerogels were compressed under uniaxial pressure (5\u0026ndash;15 MPa) to form freestanding two-dimensional (2D) membranes. Subsequently, thermal annealing (200\u0026deg;C, 2 h) was employed to reduce GO, enhancing the structural stability of the densified photothermal membrane (DPM).\u003c/p\u003e\u003cp\u003eDifferent crosslinking strategies were employed for various DPMs. Specifically, for samples containing acrylamide (AAm) and 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS), photo-crosslinking was performed by immersing the membranes in an aqueous solution of ammonium persulfate ((NH\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e8\u003c/sub\u003e, 0.1 mol L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 200 \u0026micro;L) as the initiator and N,N\u0026rsquo;-methylenebisacrylamide (MBAA, 0.1 mol L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 30 \u0026micro;L) as the crosslinker, followed by UV irradiation for 2 h. Sodium alginate (SA)-added DPMs were ionically crosslinked in CaCl\u003csub\u003e2\u003c/sub\u003e solution (0.5 mol L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) for 30 min. Trehalose (Tre)-loaded DPMs required no further treatment, as Tre was uniformly distributed within graphene sheets via strong hydrogen bonding. The resulting samples are denoted as DPM\u003csub\u003en\u003c/sub\u003e-X, where n denotes the applied mechanical compression strength (5\u0026ndash;15 MPa), and X refers to the incorporated hydrophilic polymer (PAAm, Tre, SA, and PAMPS), respectively. This precise control over n and X enables the fine-tuning of interlayer nanostructures and chemical microenvironments in DPM\u003csub\u003en\u003c/sub\u003e-X.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eMelting behavior of DPM\u003csub\u003en\u003c/sub\u003e-X by DSC assessment\u003c/h2\u003e\u003cp\u003eThe ice melting characteristics of fully hydrated samples were investigated by differential scanning calorimetry (DSC). After removing surface water, samples were completely sealed in aluminum crucibles, cooled to \u0026minus;\u0026thinsp;80\u0026deg;C at \u0026minus;\u0026thinsp;5\u0026deg;C min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, held for 30 min, and subsequently heated to 40\u0026deg;C at 5\u0026deg;C min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. All measurements were conducted under a constant nitrogen flow (50 mL min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eSDIE experiments\u003c/h2\u003e\u003cp\u003eThe SDIE performance of DPM\u003csub\u003en\u003c/sub\u003e-X was characterized using a custom-designed testing system illuminated by a xenon lamp light source (CEL-PE300L-3A) equipped with an AM 1.5 G optical filter to simulate standard solar irradiation (1 kW m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e). Samples (20 mm \u0026times; 20 mm) were subjected to continuous illumination until surface temperature stabilization. After the sample surface temperature reached a steady state, an electronic balance with a resolution of 0.1 \u0026micro;g was used to measure the difference in system mass loss before and after exposure to continuous sunlight for 1 h, thereby calculating the water evaporation rate.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003eWater purification of complex wastewater\u003c/h2\u003e\u003cp\u003eThe water purification performance of wastewater containing highly concentrated ions and strongly polar VOCs using optimized DPM\u003csub\u003e10\u003c/sub\u003e-PAMPS was evaluated using a custom-designed sealed device (effective area: 20 mm \u0026times; 20 mm) under simulated solar illumination (CEL-PF300L-3A xenon lamp, AM 1.5G spectrum). Under solar irradiation, the increased interfacial temperature provides a strong driving force for the selective evaporation of water molecules. The water purification process employed a precisely controlled feed system. To evaluate performance across diverse hypersaline conditions, feed solutions included NaCl brines with salinities of 3.5 wt%, 10 wt%, and 20 wt%, as well as mixed heavy-metal brines (Cr\u003csup\u003e3+\u003c/sup\u003e, Pb\u003csup\u003e2+\u003c/sup\u003e, Zn\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, and Cu\u003csup\u003e2+\u003c/sup\u003e in an equal mass ratio of 1:1:1:1:1) with salinities of 5 wt%, 10 wt%, 15 wt%, and 20 wt%. For the treatment of water/VOCs solutions, the VOCs, including benzene, toluene, phenol, ethanol, isopropanol, or n-butanol, with different concentrations, were selected.\u003c/p\u003e\u003cp\u003eThe original solutions were continuously delivered to the device at a constant flow rate using a precision peristaltic pump. This configuration maintained a steady-state VOCs concentration throughout the experiments. The system incorporated an air circulation with generated water vapor being condensed in a \u0026minus;\u0026thinsp;20\u0026deg;C cold trap for subsequent analysis. The quantitative analysis of VOCs was performed using high-performance liquid chromatography (HPLC, Agilent G1322A) and gas chromatography (GC, Agilent 7890B), respectively. Standard curves were established for each VOC by correlating HPLC/GC peak areas with known concentrations, ensuring accurate quantification (R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.990 for all analytes).\u003c/p\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data generated in this study are provided in the Supplementary Information and Source Data file. Source data are provided with this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eP.Z. acknowledges Prof. L.Q. and Prof. Z.J. for the helpful advice and comments. This work was supported by the\u0026nbsp;Hebei Provincial Natural Science Foundation, Excellent Youth Project (E2023202069), National Natural Science Foundation of China (22209036, U23A20119), and National Key R\u0026amp;D Program of China (2024YFF0506000, 2024YFB4609100).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eP.Z., Z.J., and J.L. performed conceptualization. Q.J., J.B., and L.W. designed the research. J.L., S.X., and Z.G. performed the methodology. J.W., J.L., and S.X. performed the investigation. P.Z. and J.L. performed Visualization; S.X. performed calculations. P.Z., Z.J., and L.Q. performed supervision. P.Z. and J.L. wrote the original draft. P.Z., Z.J., and L.Q. edited the manuscript and reviewed the file. All the authors contributed to data reduction and data analysis.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eAdditional information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSupplementary information\u003c/strong\u003e The online version contains supplementary material available at\u0026hellip;.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMekonnen MM, Hoekstra AY (2016) Four billion people facing severe water scarcity. Sci Adv 2:e1500323\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGreve P et al (2018) Global assessment of water challenges under uncertainty in water scarcity projections. 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ACS Appl Mater Interfaces 8:2097\u0026ndash;2103\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8090933/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8090933/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSolar-driven interfacial evaporation (SDIE) is a sustainable, carbon-neutral approach for freshwater production. Nevertheless, achieving both high evaporation rates and efficient removal remains challenging, especially for wastewater enriched with concentrated ions and strongly polar VOCs from chemical and electronics manufacturing. Here, we report the confined water-selective highways within a densified photothermal membrane (DPM) for ultrafast purification of such complex wastewater. Through mechanical compression and the rational selection of hydrophilic polymers, DPM’s interlayer nanostructures and chemical environments are engineered with molecular precision. Due to the synergistic effect of steric hindrance and chemical selectivity, this structure enables preferential water transport while effectively excluding highly concentrated ions and strongly polar VOCs. DPM exhibits a high water evaporation rate of 2.58 kg m\u003csup\u003e− 2\u003c/sup\u003e h\u003csup\u003e− 1\u003c/sup\u003e under 1 kW m\u003csup\u003e− 2\u003c/sup\u003e. DPM retains stable performance for over 200 h in various near-saturated hypersaline solutions (20 wt% salinity) and enables clean water harvesting from both common (e.g., benzene, toluene, phenol) and strongly polar VOCs (e.g., ethanol, isopropanol, n-butanol) even at very high concentrations. Device integration further demonstrates its scalability for treating complex wastewater, highlighting the significance of molecularly engineered interfacial architectures for efficient SDIE under challenging conditions.\u003c/p\u003e","manuscriptTitle":"Confined water-selective highways in a densified photothermal membrane enable ultrafast purification of complex wastewater","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-04 08:06:48","doi":"10.21203/rs.3.rs-8090933/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"0b897cce-45f4-477c-8fe2-610332fdd22d","owner":[],"postedDate":"December 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":59038897,"name":"Scientific community and society/Water resources"},{"id":59038898,"name":"Earth and environmental sciences/Environmental social sciences/Sustainability"}],"tags":[],"updatedAt":"2026-05-08T13:30:57+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-04 08:06:48","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8090933","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8090933","identity":"rs-8090933","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}