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Designing ultra‐light, green, and flexible films for efficient electromagnetic interference (EMI) shielding is crucial yet challenging. Herein, laminated Ti3C2Tx MXene nanosheets are prepared and impregnated into a delignified wood matrix to fabricate composite films. Through a facile drop‐casting and densification strategy, highly aligned cellulose fibers are used for regulating the stacking behavior of MXenes, and the MXenes are encapsulated and attached tightly to the cellulose chains through hydrogen bonds. A high MXene loading up to 32.5 wt.% can be realized, and the resultant MXene/wood film exhibits a tensile strength of 260.7 MPa. The EMI shielding effectiveness is calculated to be 55.5 dB (X‐band, 8.2–12.4 GHz), with a normalized surface‐specific shielding effectiveness of 2673.4 B cm2 g−1. Moreover, the superior electrical conductivity and structural robustness of the composite film give it pressure‐sensing properties and show high sensitivity for monitoring diverse human physiological movements. [ABSTRACT FROM AUTHOR]

Drill feed speed significantly affects the measurement accuracy and efficiency of the micro drill resistance instrument. Generally, different speeds are set according to the density of the wood to be drilled. It is necessary to convert the resistance data measured at different drill feed speeds into resistance data at a uniform speed to properly analyze resistance data. In this study, drill resistance data for a Paulownia wood block was measured with a self-made micro drill resistance instrument at different drill feed speeds. We found that the drill resistance is positively correlated with changes in its feed speed and the natural logarithm of change times for feed speed. We developed a conversion algorithm for the micro drill resistance instrument measurements at different feed speeds. The accuracy of the conversion algorithm is up to 95%. The algorithm can be used to convert the drill resistance of Paulownia wood measured at different drill feed speeds; it has reference value for the mutual conversion of other tree species' drill resistance data measured at different feed speeds. This work may provide a feasible solution to improving micro drill resistance instrument accuracy when drill feed speed error is high. [ABSTRACT FROM AUTHOR]

Wood sponges obtained by structure-retaining delignification of natural wood sheets are promising for CO2 storage. Herein, lignin in balsa wood is selectively removed through chemical treatment, leading to a highly porous structure. To boost the CO2 adsorption capacity, amine agents are grafted on the delignified wood via a condensation reaction. The resulting amine-grafted wood sponges exhibit hierarchical porosity and are mechanically resilient. A relatively high CO2 uptake of 1.22 mmol g−1 (25 °C, 1 bar) is achieved due to the physisorption of hierarchical pores and chemisorption of high amine group loading. Such amine-grafted wood sponges fabricated from top-down strategy hold great potential to serve as renewable CO2 capture materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • MOF-based wood air filters were prepared and applied to air filtration. • MOF particles were attached tightly to the wood channel matrix. • Compound air filters can effectively remove particulate matter. • The trapping mechanism of particulate matter by MOF in wood cavity was proposed. The severe indoor/outdoor air contamination caused by hazardous particulate matters (PMs) has a devastating impact on the environment and human health. Herein, air filters fabricated from delignified wood aerogels and metal–organic frameworks (MOFs) were used for PM removal. Two specially designed MOFs (i.e. Zn-based ZIF-L and Zr-based UiO-66-NH 2) were deposited into a highly porous wood matrix through in situ growth approach. The MOF crystals are attached tightly to the highly available cellulose surface groups and distributed uniformly. The integration of MOFs can regulate the aerogel morphology and surface property, leading to enhanced PM removal performance. Bare wood aerogels beard removal efficiencies of 70.7% and 75.0% for PM 2.5 and PM 10 , with a low-pressure drop of 15 Pa. By contrast, ZIF-L decorated wood aerogels exhibited PM 2.5 and PM 10 removal efficiencies of 97.6% and 99.5%, respectively, which are ascribed to the increased interception/impaction of PMs with the positively charged ZIF-L layer. While UiO-66-NH 2 functionalized wood aerogels demonstrated PM 2.5 and PM 10 removal efficiencies of 96.4% and 98.9% because of the hierarchical filter matrix and the presence of polar –NH 2 groups. Moreover, MOF modified wood aerogels can be easily regenerated and superior reusability can be achieved. This work provides an effective and economic strategy for the preparation of air filters from renewable materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Research progress in the preparation of wood hydrogels by the top-down method is reviewed. • The advantages of wood hydrogels in structure and property are highlighted. • The relationship between wood hydrogel preparation-properties-applications is elucidated. • The challenges and outlooks for the future development are presented. Wood-based materials have attracted increasing interests due to the progress of wood nanotechnology. In such cases, wood hydrogels fabricated by a top-down approach demonstrate huge potential in smart electronics, sensors, biomedical and energy harvesting/storage devices. Distinct from cellulose or lignin hydrogels prepared from bottom-up technology, wood hydrogels retain the hierarchical/anisotropic structure of natural wood. In addition, wood hydrogels can be produced in a facile, scalable and energy-saving way. In this short review, a brief overview of the recent development of wood hydrogels is provided, with special emphasis on the preparation methods and structural characteristics. The various applications of wood hydrogels are then discussed from a preparation-performance-application point of view. This is followed by a summary of the challenges and perspective for the future improvement of wood hydrogels, as well as guidance for the development of green scalable wood-based functional polymeric materials. [ABSTRACT FROM AUTHOR]

Three-dimensional and lightweight carbon aerogels are promising for next-generation wearable devices. As the most abundant renewable resource on the planet, wood provides a green and sustainable raw material for the manufacture of lightweight and elastic carbon materials. Here, a simple and sustainable design is proposed to directly prepare elastic carbon aerogel with a layered structure from the wood. Zeolitic imidazolate framework (ZIF-L) was deposited on a wood aerogel matrix without lignin and hemicellulose by in situ growth. The presence of ZIF-L significantly reduced the volume shrinkage of aerogel during carbonization, and the carbonized ZIF-L improves the contact area and provides electron transport path. The prepared aerogel has a stress of 42 kPa under 80% strain, and the elastic strength and volume remain both above 98% after 200 times of compression, indicating that the aerogel has excellent compressibility and fatigue resistance. Based on this particular structural design, as-obtained aerogel shows excellent sensitivity as pressure sensors to detect subtle signals. In addition, the carbon aerogel can be directly assembled into a all-solid-state symmetric supercapacitor that show promising electrochemical performance and could be potential candidates for high-performance supercapacitors in wearable devices. [Display omitted] ● Carbonized wood aerogel was prepared via a top-down method. ● ZIF-L reduced the volume shrinkage of aerogel during carbonization. ● Carbonized wood aerogel has excellent elastic properties and fatigue resistance. ● Carbonized wood aerogel monitors physiological signals and energy storage. [ABSTRACT FROM AUTHOR]

[Display omitted] • Deep eutectic solvent (DES) was applied for wood delignification. • DES was used as precursor for the growth of ZnO particles. • ZnO was attached tightly and uniformly to the wood matrix. • ZnO deposited carbon foam displayed a high CO 2 adsorption capacity. • The ZnO@carbon foam presented a good oil absorption and flame-retardant property. Wood-derived carbon materials with high porosity are promising for gas capture and wastewater treatment. In this work, ZnO coated carbon foams were fabricated by in situ growth of ZnO crystals on the biomass scaffold. A specially designed deep eutectic solvent (DES) composed of ZnCl 2 and lactic acid was utilized for wood delignification. In particular, the DES has a dual role as a lignin removal agent and ZnO precursor. After carbonization, spherical ZnO particles were uniformly and tightly deposited on the carbonized balsa wood matrix. The interconnected channels of pristine wood are well inherited by the carbon foam. The ZnO@carbon foam (DW-800) prepared with a carbonization temperature of 800 °C displayed a specific surface area of 446 m2/g, and a water contact angle of 133°. The CO 2 adsorption and oil absorption tests were performed to evaluate the applied performance of the composites. Results demonstrated that DW-800 showed a superior CO 2 adsorption capacity of 3.03 mmol/g (25 °C, 1 bar). Moreover, the flame-retardant DW-800 possessed a desirable oil/water separation ability for both heavy oil and light oil. This work presents a facile, low-cost and top-down approach to the fabrication of wood-derived carbon materials. [ABSTRACT FROM AUTHOR]

The fabrication of cellulose hydrogels from nature-abundant wood through a top-down strategy has attracted extensive attention. However, simultaneous realization of superior mechanical strength and ionic conductivity is a huge challenge. Herein, highly anisotropic, flexible, and conductive wood hydrogels were prepared by a designed double cross-linked strategy. By integrating acrylamide/acrylic acid and Fe3+ ions into the delignified wood matrix, the mechanical performance and ionic conductivity can be largely enhanced. The optimal sample demonstrated a tensile fracture strength of 8.2 MPa along the tree growth direction, high conductivity of 0.040 S/m. The resulting hydrogels were assembled into sensors and used to monitor diverse human activities, and they could realize highly sensitive and durable human motion detection. This work provides a new direction for the design of wood-based human motion sensors. [Display omitted] [ABSTRACT FROM AUTHOR]

• Wood-based air filters were fabricated and applied for air filtration. • Three MOFs were integrated into the filter matrix to boost filtering performance. • MOF decorated wood filter presents superior PM capture performance. • The PM path and capture mechanism of PMs in wood lumens are proposed. Particulate matter (PM) pullution has emerged as a global concern. Herein, delignified wood functionalized with metal–organic frameworks (MOFs) was investigated for efficient PM removal. In particular, the lignin removal was realized by a deep-eutectic-solvent assisted process. By integrating three different MOFs into the porous wood matrix, wood-based filters with hierarchical structure were fabricated. The MOF particles including ZIF-8, MOF-199 and UiO-66 were deposited on the filters through in situ growth approach, thereby leading to a uniform MOF dispersion and strong wood-MOF adhesion. The ZIF-8 functionalized wood filter exhibited the highest PM removal performance, with PM 2.5 and PM 10 removal efficiencies of 89.8% and 91.6%, respectively. The superior PM capture ability of ZIF-8@Wood is attributed to the suitable surface property and sophisticated channels/pores. The gas transport pathways and PM capture mechanisms within wood filter were discussed in detail. This cost-effective and environmentally friendly filtration device provides a novel material platform for PM removal, and it could be extended for hazardous gas capture and volatile organic compound adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu-CAT MOF was used as solar absorber for efficient water purification. • The superoleophobic MOF layer was integrated onto the bottom side of wood substrate. • The wood evaporator with a sandwich-like structure presents a good anti-oil-fouling property. • An evaporation rate of 1.80 kg m−2h−1 under 1 sun illumination was obtained. By utilizing sunlight, the interfacial solar evaporation system is promising for seawater desalination, wastewater decontamination and electricity generation. Herein, a copper-based metal organic framework (Cu-CAT) was coated on wood sheets to form a wood evaporator, and the wood substrate with a low thermal conductivity is in charge of continuous water transportation. The Cu-CAT layer was attached tightly to both the top and bottom surfaces of the wood substrate. The black Cu-CAT at top surface affords a broadband and strong light absorption, while the underwater superoleophobic Cu-CAT layer presents a high oil repellence. Through optimizing the wood substrate thickness, the wood evaporator (Cu-CAT/Wood) with a wood thickness of 10 mm displayed an evaporation rate of 1.80 kg m−2h−1 under simulated 1 sun illumination. Enabled by the Cu-CAT, the wood evaporator can be used for water purification from various sources (seawater, oil-, dye-, heavy metal- contaminated water and natural lake water). Importantly, the Cu-CAT/Wood could co-generate electricity induced by the solar vaporization process. This work will stimulate more studies on the structural designs of solar evaporators for drinkable water production and pollution abatement. [ABSTRACT FROM AUTHOR]

• ZIF-8 is coated on the aligned wood channels to form ZIF-8/wood composites. • The crystallinity and adsorption function of ZIF-8 were well maintained. • The ZIF-8/wood was assembled into a filter system for wastewater purification. • The ZIF-8/wood composites have stable chemical properties and good recyclability. The practical application of ZIF-8 crystals is commonly limited by their powder form. In this work, natural balsa wood sheets were employed as substrate for dispersing and shaping ZIF-8 particles. By in situ growth method, ZIF-8 layer was coated on the aligned wood channels to construct ZIF-8/wood composites with a hierarchical structure. A good affinity and interfacial compatibility between ZIF-8 and wood lumens was observed. The wood channels enable high-speed water transport and the ZIF-8/wood composites were integrated into filtration systems for continuous wastewater treatment. At a 7.9 wt% ZIF-8 loading, the three-layered ZIF-8/wood filter (ZW-2) presented an effective treatable volume of 800 mL of 10 mg L−1 Cu2+ solution. Moreover, ZW-2 exhibited an excellent recyclability and reusability. Such wood-based composite is renewable, low cost, and holds great potential for practical environmental remediation. [ABSTRACT FROM AUTHOR]

Wood-based solar desalination is emerged as one of the promising methods to address the water shortage problem. Herein, a wood evaporator was designed by a two-layer structure: a hydrophobic top layer (Fe 3 O 4) and a superhydrophilic delignified wood bottom layer. The Fe 3 O 4 coated delignified wood (Fe-D-Wood) demonstrates an evaporation rate of 1.3 kg m−2 h−1 and a conversion efficiency of 73%. Fe 3 O 4 with a narrow bandgap (0.8 eV) affords a broad light absorption and polyvinyl alcohol (PVA) enhances the affinity between Fe 3 O 4 and wood substrate, and the wood evaporator presents a good anti-fouling property. Two reasons contribute to such self-regenerating ability: i) salts are difficult to deposit on the hydrophobic layer, and ii) the rapid water uptake promotes the re-dissolution of salts into bulk water. Such wood-based evaporator holds great potential for practical desalination applications. [Display omitted] • Fe 3 O 4 is used as solar absorber for efficient desalinization. • Wood substrate is delignified to optimize the thermal and wetting properties. • Polyvinyl alcohol is introduced to enhance the affinity between Fe 3 O 4 and wood. • The wood evaporator presents a good anti-fouling property. • Fe-D-Wood demonstrates a solar thermal conversion efficiency of 73%. [ABSTRACT FROM AUTHOR]