Fig. 1

The molecule structure of cellulose (n=DP, Degree of polymerization) and Intra- and intermolecular hydrogen bonds in cellulose"

Fig. 2

Graphical illustration of the hierarchical structure of wood, from macroscopic to molecular scale[3]"

Table 1

The mechanical properties of several different materials[4, 6-9]"

Fig. 3

(a) Reaction scheme illustration of the simultaneous occurrence of cellulose hydrolysis and esterification of hydroxyl groups using a mixture of acetic and hydrochloric acid as example[11]. (b) The preparation of nanocellulose under the pretreatment by the natural deep eutectic solvent (NADES) composed of lactate (LA) and choline chloride (CC)[19]. (c) Schematic diagram of the fabrication of CNCs through MwDES pretreatment and a subsequent high-intensity ultrasonication process. Optical photographs and polarized optical microscope images of the MwDES-pretreated CFs and the corresponding CNC suspensions: (d), (h) MwDES-70, (e), (i) MwDES-80, (f), (j) MwDES-90, and (g), (k) MwDES-100[21]"

Fig. 4

Several conventional methods of surface modification of cellulose and different cellulose based multifunctional materials[22-27]"

Fig. 5

Cooling wood demonstrates passive daytime radiative cooling. Photos of (a) natural wood and (b) cooling wood. (c) SEM image of the cooling wood showing the aligned wood channels. (d) SEM image of partially aligned cellulose nanofibers of the cooling wood. (e) Schematic diagram of the wood structure strongly scattering solar irradiance. (f) Schematic diagram of infrared emission by molecular vibration of the cellulose functional groups. (g) Setup of the real-time measurement of the sub-ambient cooling performance of the cooling wood[29]. (h) Fabrication process of the cooling lignocellulosic bulk by low cost cellulose and silicon dioxide. (i) Bending stress curves, (j) tensile stress curves for the cooling lignocellulosic bulk and pure wood fibers bulk. (k) Schematic diagram of the cooling lignocellulosic bulk with infrared emission and scattering solar irradiance. (l) Schematic diagram of the thermal box for demonstrating radiative cooling performance. (m) A 2-day continuous measurement of radiative cooling power, the ambient temperature (black) and the surface temperature (red) of a cooling lignocellulosic bulk under direct thermal testing[30]"

Fig. 6

Construction and characterization of aerogel coolers. (a)—(c) Preparation process for ultralight and upscaling aerogel coolers. (d) Interior and top surface morphology of aerogel coolers. (e) Chemical bonds and proposed mechanism of radiative emittance of aerogel cooler. (f) Cooling performance of aerogel coolers at a wind speed of 6 m/s and a relative humidity of 30%. (g), (h) Cooling performance of aerogel coolers at a wind speed of 3 m/s and a relative humidity of 70%[31]"

Fig. 7

Design of plasmonic wood. (a) A tree transports water from the bottom upward and absorbs sunlight for photosynthesis, (b) the natural wood decorated with plasmonic metal nanoparticles (c) a schematic of light is guided into the wood lumen and is fully absorbed for steam generation, (d) Schematic of plasmonic effect of two adjacent metal nanoparticles (NPs), (e) Zoomed-in schematic illustrating the water transport along microchannels in wood, (f) Absorption curves for plasmonic wood decorated with Pd nanoparticles and natural wood, (g) IR pictures of plasmonic wood under various illumination intensities[38], (h) Schematic of the scalable device manufacturing process, (i) SEM image of mesoporous wood with the wood lumens aligned along the wood growth direction (j) Schematic showing the solar steam generation mechanism of the graphite-coated wood, Evaporation rate (k) and Cycling performance (l) of graphite coated wood under 1 Sun condition[39]"

Fig. 8

(a) Schematic diagram of a typical solar steam generation device, (b) Optical microscope picture of PEDOT:PSS-NFC aerogel, (c) Scanning electron microscopy (SEM) image of PEDOT:PSS-NFC aerogel, (d) Chemical structures of PEDOT:PSS, GOPS, and NFC, (e) The absorptance of PEDOT:PSS-NFC film, 1 mm thick aerogel, and 2 mm thick aerogel[40], The preparation process of all-cellulose-based steam generator (SG2) (f) and schematic illustration of interface interaction (g) in the steam generators, (h) Water evaporation rates in dark and light conditions, (i) water evaporation rates of SG2 under different solar intensities and air flows[41]"

Fig. 9

(a) Schematic of synthesis procedure for CNF@c-MOF hybrid nanofibers, (b) Photograph of an origami folded by CNF@Ni-HITP nanopaper[43], (c) gold-patterned cellulose films reineforced by nano Si pellets. Resistance measurements as a function of bending angle (d), bending cycle (e), and number of folds (f)[44], (g) Fabrication process of flexible hydrophobic cellulose paper (HCP), (h) The photo of TENG constructed by HCP (i) VOC signals under walking behavior using HCPTENG[45]"

Fig. 10

Schematic illustration of the tree-inspired tri-pathway design for flexible Li-O2 cells. (a) Multiphase transport (e.g., water, ions, and nutrients) are essential for photosynthesis in trees. (b) A tri-pathway structural design was realized by chemically treating natural wood to remove lignin and hemicellulose (endowing it with flexibility) and subsequent CNT/Ru coating to provide electron conductivity and catalytic activity to enable the noncompetitive triphase transport of Li+, electrons, and oxygen gas[46]"

Fig. 11

(a) Schematic illustration of the manufacturing of the CPC separator, (b) Wettability and thermal stability of pristine PE and CPC separators, (c) SEM images of the Li deposits on Cu electrodes used in Li/Cu cells comprising a CPC (right) separator at a deposition current density of 1.5 mA/cm2[49], (d) Schematic illustration depicting the evaporation-induced self-assembly (EISA) process-driven fabrication of the self-assembled chiral nematic liquid crystalline cellulose nanocrystal (LC-CNC) layer on a polyethylene (PE) separator and its chemical structure, (e) Cross-sectional scanning electron microscopy (SEM) image of the EC separator (consisting of the LC-CNC layer (thickness ～3 μm) and PE separator (～7 μm), (f) Cross-sectional SEM image of the Li-metal after the unidirectional Li plating using the EC separator (vs. pristine PE separator (inset) for 90 h, (g) Amount of Mn2+ ions trapped by the EC separator (vs. pristine PE separator)[53]"

Fig. 12

Fabrication of symmetrical supercapacitors (SSC) based on enzymolysis-treatment of wood-derived hierarchically porous carbon thick electrode[62]"