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[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]

Abstract: Acid-catalyzed esterification and transesterification reactions, suitable for biodiesel production from high acid value oils, face a problem of long reaction time. In this study, we developed a two-step process for fast acid-catalyzed biodiesel production from high acid value oil in a microstructured reactor, which was assembled with an SIMM-V2 micromixer connected with a 0.6mm i.d. stainless steel capillary. Esterification of oleic acid and transesterification of cottonseed oil with methanol were separately carried out to find suitable reaction conditions. The influences of the residence time, the methanol to acid/oil molar ratio, the catalyst concentration, the water/acid concentration and the reaction temperature were examined. The highest oleic acid conversion was obtained when esterification of oleic acid with methanol was carried out at 100°C with the residence time of 5min, while the highest yield of fatty acid methyl ester (FAME) was achieved when transesterification of cottonseed oil with methanol was conducted at 120°C with the residence time of 20min. Thereafter, a two-step process was developed based on the above reaction conditions with the first and second steps separately conducted under the esterification and transesterification reaction conditions. The results indicated that the acid value of the acid oil was reduced from 160 to 1.1mg KOH/g with a methanol to acid molar ratio of 30, the H2SO4 concentration of 3wt%, a residence time of 7min at 100°C in the first step. The final FAME yield reached 99.5% with a methanol to triglyceride molar ratio of 20, the H2SO4 concentration of 3wt%, a residence time of 5min at 120°C in the second step. Therefore, biodiesel production from high acid value oil can be continuously achieved at high yields by acid-catalyzed transesterification in microstructured reactors with total reaction times of less than 15min. [Copyright &y& Elsevier]

Abstract: Sulfonated carbon–silica composites with surface areas of over 600m2/g and pore sizes of 1.5–2.2nm were prepared by incompletely carbonizing sucrose dispersed on MCM-48 and sulfonating the obtained carbon/MCM-48 composites. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, N2 adsorption, energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy. The catalytic activities of these composites were studied in the esterification of acetic acid with n-butyl alcohol. The pore sizes and catalytic activities of the sulfonated carbon–silica composites were adjustable by changing the amount of sucrose loadings, and the composites exhibited enhanced hydrothermal stability and amphiphilic property. When the sucrose loading was close to the monolayer dispersion capacity of sucrose on MCM-48 (1.1g sucrose/g MCM-48), the resulting sulfonated carbon–silica composites exhibited surface areas of 700–724m2/g and n-butyl acetate yields of 90.4–98.7% in the esterification of acetic acid with n-butyl alcohol. They also showed obvious catalytic activities in the esterification of long-chain fatty acids with ethanol. The expensive MCM-48 could be easily recycled by simply calcining the sulfonated carbon–silica composites in air. [Copyright &y& Elsevier]

• A self-crosslinking strategy to combine UiO-66 and nanocellulose is proposed. • A hierarchically structured MOF/cellulose aerogel was synthesized. • The micropores and accessibility of UiO-66 were well-preserved. • The UiO-66 loadings could reach up to 50 wt%. • The strategy opens a door for processing MOFs into a flexible form. Composite UiO-66/nanocellulose aerogels with hierarchical pores and low density were prepared through a self-crosslinking method. The nanocellulose acted as the structural skeleton supporting and dispersing the UiO-66 particles. The micropore and accessibility of UiO-66 were well-preserved, making the composite aerogels ideal sorbents for water purification. The composite aerogels demonstrated high adsorption ability towards both anionic methyl orange (71.7 mg g−1) and cationic methylene blue (51.8 mg g−1). This work holds a promise to rational design and fabrication of MOF monoliths through group linkage. [ABSTRACT FROM AUTHOR]

[Display omitted] • This work reports a 3D boron-doped carbon nitride with frustrated Lewis pairs and defects. • The honeycomb-like 3D CN presents an improved nitrogen electro-fixation rate. • The frustrated Lewis pairs accelerate N 2 chemisorption and activation. • The 3D structure favors the contact between the electrolyte and the active sites. It is of great importance to explore metal-free electrocatalysts with high electrocatalytic nitrogen reduction reaction (NRR) activity for ammonia (NH 3) production. This work for the first time reports a three-dimensional (3D) boron (B) doped carbon nitride with frustrated Lewis pairs and deficiencies for efficient NRR via a facile copolymerization of sodium borohydride and urea precursors. The texture and the amount of B dopants in the resultant 3D carbon nitride can be finely tuned by varying the dosage of sodium borohydride. With the optimal B-doping content, the formed honeycomb-like 3D catalyst has a high NH 3 yield rate of 17.8 μg h−1 mg−1 and Faradaic efficiency of 9.85% in 0.1 M Na 2 SO 4 and 0.05 M H 2 SO 4 electrolyte at −1.4 V vs RHE, which is considerably better than the undoped 3D carbon nitride. Comprehensive characterizations reveal that for the B-doped 3D carbon nitride, the unique 3D structure makes more introduced cyano groups and exposed nitrogen defects, favoring the contact between the electrolyte and the active sites. The abundant unsaturated B and N atoms function as frustrated Lewis pairs to strengthen N 2 chemisorption and activation, lowing the barrier of NRR and meanwhile suppressing hydrogen evolution reaction. Moreover, in-situ UV–vis spectroscopy elucidates that the optimal potential at −1.4 V vs RHE benefits free electrons to participate in the NRR reaction because it matches the conduction potential of B-UCN-15. This study provides a new avenue for the rational design of nonmetal-based catalysts for NRR. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrostatic self-assembly SnO 2 QDs-TQDs composite materials were fabricated. • SnO 2 QDs-TQDs could effectively engineer the ETL and perovskite/ETL interface. • TQDs modified perovskite exhibits reduced defect density and passivated grain boundaries. • PCE of 23.47 % for PSCs, responsivity (35.54 mA W−1) and response speed (154 ms) for PPDs were achieved. The performance of perovskite solar cells and photodetectors strongly depends on the carrier extraction in the electron transport layer/perovskite interface and the film quality of the perovskite layer. Ti 3 C 2 T x MXene quantum dots, which exhibit both good conductivity of MXene materials and size-dependent tunable optoelectronic properties of quantum dots, were synthesized to form electrostatic self-assembly nanoparticles and further introduced into perovskite optoelectronic devices. The carrier extraction in electron transport layer/perovskite interface was significantly improved, and the defect density of the modified perovskite layer was effectively reduced. These improvements ultimately lead to a remarkable power conversion efficiency of perovskite solar cells increasing from 16.57 % to 23.47 %, and the photodetectors achieve responsivity approaching 35.54 mA W−1 and response speed of 154 ms (rise time) and 120 ms (decay time). Meanwhile, the long-time humidity, thermal and light stress stability of the devices were largely boosted, which originated from the better crystallization and suppressed degradation of the perovskite films. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tunable heterojunctions of Cu x O nanoparticles anchored on CNNTs were prepared. • Annealing under H 2 /Ar (5% H 2) gases ensured a Cu 2 O@CuO/CNNTs Z-scheme heterojunction. • Treating under static air led to a CuO/CNNTs Type II heterojunction. • Cu 2 O@CuO/CNNTs exhibit improved photocatalytic nitrogen fixation efficiency. • Cu 2 O@CuO interface offers a high N 2 adsorption ability. Tunable Cu x O (core–shell structured Cu 2 O@CuO and CuO) nanoparticles (NPs) are finely loaded on carbon nitride nanotubes (CNNTs) using a facile one-pot method but annealing under different atmospheres. Calcining under H 2 /Ar (5% H 2) ensured a Z-scheme heterojunction of Cu 2 O@CuO/CNNTs, and core–shell nanostructured Cu 2 O@CuO NPs in particle size of 20–80 nm are firmly anchored along the nanochannels of CNNTs. Calcining under static air conditions led to a Type II heterojunction of CuO/CNNTs, and larger CuO NPs of ca. 200 nm are on the surface of CNNTs. The effect of the calcination temperature and loading content on the photocatalytic ammonia yield was studied. With the annealing temperature at 400 °C and 9 wt% copper percentage, the resulting Z-scheme Cu 2 O@CuO/CNNTs exhibit a nitrogen photofixation rate of 1.38 mM g cat –1h−1 with an apparent quantum efficiency of 6.28% at 420 nm, which is about 1.4 and 4.4 times higher than that of CuO/CNNTs and the bare CNNTs, respectively. Introducing Cu 2 O cores upshifts the band positions of the Cu x O NPs, resulting in the formation of a Z-scheme band structure. Comprehensive characterizations reveal that compared to Type II CuO/CNNTs, Z-scheme Cu 2 O@CuO/CNNTs offer higher N 2 chemisorption energy, accelerated charge carrier transfer and increased photoreduction capability. This study provides a reliable and promising route to engineer core–shell structured Z-scheme heterojunctions for enhanced photocatalytic nitrogen fixation. [ABSTRACT FROM AUTHOR]

• This work reports highly crystalline S-doped CNNTs with tunable geometry. • S-CNNTs-20 exhibit an enhanced visible-light photocatalytic N 2 fixation rate. • High crystallinity and S-N coordination firmly stabilize the surface N in S-CNNTs-20. • The synergistic effect is due to high crystallinity, S dopant and holey tubular form. Highly crystalline carbon nitride nanotubes doped with sulfur (S-CNNTs) were obtained from a facile co-polymerization of thiourea and melamine precursors. The geometry, crystallinity and the doped S content in CNNTs can be fine-tuned by varying the content of thiourea. Under the addition of 20 wt% thiourea, the resulting highly condensed S-CNNTs have a diameter of around 20 nm with mesopores on the tube wall, presenting an optimal visible light photocatalytic ammonia yield rate of 0.64 mM g cat –1h−1 with an apparent quantum efficiency of 5.65% at 420 nm. The surface N atoms in the optimal photocatalyst can be firmly stabilized due to the increased crystallinity and S-induced coordination. The high crystallinity and one-dimensional mesoporous structure promote the electron transfer along the longitudinal dimension, facilitate mass transport and extend visible light harvesting. The mesoporous nanotubes favor the exposure of S dopant active sites for the chemisorption and activation of nitrogen molecules. Moreover, the photoreduction ability is improved due to the upshifted conduction band level after S doping. The designed structure maximizes the utilization of the synergistic effect, thereby improving the photocatalytic activity. This work may provide a reliable and promising way to regulate the morphology and electronic structure of tubular CN for highly efficient photocatalysis via a nonmetal doping approach. [ABSTRACT FROM AUTHOR]

• A simple method for Ni-doped ZnO with oxygen vacancies was developed. • 3ZnO with 3 wt% of Ni2+ doping got 94% depolymerization of sodium lignosulfonate. • The optimal yields of vanillic acid and guaiacol were 9.3% and 1.5%, respectively. • Suitable concentration of oxygen vacancies promotes the production of of •O 2 -. • O 2 − is useful to depolymerization of sodium lignosulfonate into valuable product. Oxygen vacancies are efficient to promote the separation of photogenerated electrons and holes, thereby enhancing the photocatalytic performance of the catalyst. In this work, Ni-doped ZnO with oxygen vacancies was successfully synthesized. 3ZnO with 3 wt% of Ni2+ doping has an optimum photocatalytic activity. The optimal depolymerization rate of sodium lignosulfonate (SLS) was 94%, and the optimal yields of vanillic acid and guaiacol were 9.3% and 1.5%, respectively. 3ZnO can effectively depolymerize SLS to valuable products, CO 2 and H 2 O due to proper concentration of surface oxygen vacancies induced by Ni2+ doped, which promotes the formation of •O 2 –. •O 2 – is considered to be more conducive to depolymerization of SLS to valuable products. Proper concentration of oxygen vacancies is very necessary for depolymerizing SLS into valuable products. This work will give an innovative vision for efficient depolymerizing biomass to valuable products through photocatalytic reactions. [ABSTRACT FROM AUTHOR]

• PEGylated deep eutectic solvent is used for mild synthesis of CdS. • Core-shell CdS@CeO 2 photocatalyst was successfully synthesized. • The degradation of tetracycline is as high as 91.5% by optimal photocatalyst. • CeO 2 coating helps effectively reduce the photo-corrosion. As ionic liquid analogues, deep eutectic solvents (DESs) have been widely used in many fields in past decades. In this work, a PEGylated deep eutectic solvent (PEGylated DES) was used for the solvothermal synthesis of CdS@CeO 2 core-shell material for the first time. The amount of CeO 2 coating has a remarkable influence on the photocatalytic degradation of tetracycline. When the molar ratio of CeO 2 to CdS is 1:1, the degradation rate of tetracycline is 91.5% under visible light (λ > 420 nm), which is about 1.57 and 10.5 times as that of CdS and CeO 2 , respectively. The enhancement of photocatalytic performance is due to the fast separation of photogenerated electrons, the lower recombination of electron-hole pairs and the smaller band gap, which are demonstrated via UV–vis diffuse, photocurrent density, electrochemical impedance spectroscopy, photoluminescence and Mott-Schokkty measurements. This work provides a new way for the design of a core-shell metal sulfide photocatalyst that can be used in environmental remediation. [ABSTRACT FROM AUTHOR]

• The presence of COO–-Zn2+ between CNFs and ZnIn 2 S 4 leads to the 3D netted structure. • The photocatalytic activity of Cr(VI) reduction highly enhanced over CNFs/ZnIn 2 S 4. • The 3D netted structure strengthen the light via light penetration and scattering. • The enhanced photocatalytic activities are caused by the unique 3D netted structure. High-performance three-dimensional (3D) netted ZnIn 2 S 4 was achieved by the ionic connection between COO– of TEMPO-cellulose nanofibrils (CNFs) and Zn2+ of ZnIn 2 S 4 via a facile one pot synthesis. The newly-formed COO–-Zn2+ bond connection was clearly confirmed by the shifts of relative peaks in their Fourier transform infrared and X-ray photoelectron spectroscopy spectra. The prepared CNFs/ZnIn 2 S 4 composites exhibited dramatic enhancement of photocatalytic activity for Cr(VI) reduction under visible-light irradiation compared to that of pure ZnIn 2 S 4 and CNFs. Particularly, the photocatalytic efficiency of C/ZIS-0.4 (40 wt% CNFs to ZnIn 2 S 4) is 2.1 times as high as that of pristine ZnIn 2 S 4 (CNFs have almost no photocatalytic activity). On the basis of all experimental results, it can be deduced that the specific 3D netted structure of CNFs/ZnIn 2 S 4 could provide much efficient light-harvesting triggered by light penetration and scattering, abundant exposed active sites, decreased charge transport distance and good hydrophilia, which are responsible for its boosted photocatalytic activity. This study could enlighten people for developing high-efficiency photocatalysts via morphologies design guided by bond connection. [ABSTRACT FROM AUTHOR]