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Both one‐pot catalytic conversion of furfural (FAL) to isopropyl levulinate (PL) and carbonization of by‐product (humins) for electromagnetic wave absorption are discussed, which provides inspiration that humins can be applied to electromagnetic wave absorption. In the former, phosphotungstic acid (PW) is employed as a homogeneous catalyst to convert FAL to PL via a tandem reaction in one pot, with the formation of a vast amount of humins. With FAL and various intermediates as substrates, it was found that humins was a polymerization product of FAL, furfuryl alcohol (FOL) and furfuryl ester (FE) with furan rings. In addition, the in situ attenuated total reflection infrared (ATR‐IR) spectra also provided a basis for the proposed reaction route. In the latter, with the humins as raw material, P species and WO3 doped nano‐porous carbon (Humins‐700) platform formed after high‐temperature annealing is used for electromagnetic wave absorption and manifests desirable absorption performance. The minimum reflection loss (RLmin) value is −47.3 dB at 13.0 GHz with a thickness of 2.0 mm and the effective absorption bandwidth reaches 4.5 GHz (11.2–5.7 GHz). [ABSTRACT FROM AUTHOR]

A hollow core–shell magnetic zirconium hydroxide catalyst was synthesized and employed for the catalytic transfer hydrogenation (CTH) ofnumerous biomass-derived platform molecules (furfural and other carbonyl compounds). 93.9% conversion of furfural and 97.3% selectivity of furfuryl alcohol was achieved under mild reaction conditions (160 °C, 4 h, 0.1 g catalyst) with 2-propanol as the H-donor. After 7 times of reaction cycles, the catalyst retained excellent conversion (91.1%) and selectivity (97.8%) and no structural damage was found. Furthermore, a scale-up experiment was carried out, and the results proved that the catalyst has a prospect for industrial applications in the CTH reaction. [ABSTRACT FROM AUTHOR]

A simple basic zirconium carbonate (BZC), which can be produced on a large scale in industry, was studied for hydrogen transfer of biomass-derived carboxides and exhibited excellent catalytic properties at low temperatures, especially for the conversion of furfural (FUR) to furfuryl alcohol (FFA). With the catalyst, the reduction reaction of FUR was efficiently performed at low temperatures (below 100 °C) and an FFA yield of 98.66% was obtained even at room temperature. When the temperature reached 180 °C, the yield of FFA quickly reached 90.29% within 15 minutes. During the reaction, the changes of the functional groups of the reactants and products were monitored by in situ ATR-IR spectroscopy in real time, which provided a basis for the proposed reaction mechanism. Further, the ATR-IR spectroscopy and XPS results of the different catalysts showed that BZC has the strongest acidity among all the comparative catalysts, which is consistent with its best catalytic performance. In addition, reaction kinetics were also studied. [ABSTRACT FROM AUTHOR]

• Four acid-modified MOF-808 were synthesized by a post-synthesis approach. • The acidity and electron acceptor capacity of the acid groups affect B/L acidity. • Zr-808-TF has the strongest Lewis and Brønsted acidity and the highest B/L ratio. • Zr-808-TF gave 83 % GVL yield (160 °C, 8 h) in the tandem conversion of FUR to GVL. The one-pot tandem conversion of furfural (FUR) to γ-valerolactone (GVL) is desirable due to the high value of GVL and the efficiency of the synthesis process. While MOF-808 presented a good catalytic potential among Zr-MOFs, it lacked the necessary Brønsted acidity for the tandem conversion. In this study, Zr-based metal–organic framework (MOF-808) was modified with acids of different strengths (triflic acid, sulfuric acid, sulfamic acid, and trifluoroacetic acid) using a two-step post-synthesis impregnation method. EPR results revealed the appearance of coordinatively unsaturated sites of Zr (Zr-CUS) in the first step of HCl-treated Zr-808-HCl and their disappearance in the subsequent acid-modified catalysts, clarifying the impregnation process. These modified frameworks (Zr-808-TF, Zr-808-S, Zr-808-SN, and Zr-808-CF) were employed as catalysts for the tandem conversion of FUR to GVL. Zr 3d XPS and solid-state 31P MAS NMR spectra of TMPO adsorbed on the catalysts proved that Zr-808-TF outperformed other catalysts in terms of both Brønsted/Lewis acid strength and ratio. With such catalytic active sites, Zr-808-TF exhibited superior catalytic activity, achieving 83% GVL yield over an 8-hour reaction period. The four acid-modified catalysts not only differed in Lewis/Brønsted acid sites, but also exhibited different catalytic performances in the tandem conversion. The in-depth insight into the relationship between the modified functional groups and the acid-base sites provides a new avenue to optimize the acid-base sites and expands the application of MOFs in cascade catalysis. [ABSTRACT FROM AUTHOR]

Polyoxometalate-based metal-organic frameworks (POMOFs) with bifunctional Lewis-Brønsted acid were designed by confining polyoxometalates (POMs: phosphotungstic acid (PW), phosphomolybdic acid (PMo) or silicotungstic acid (SiW)) within the Zr-MOFs. The confined POMs not only have their own Brønsted acid, but can also regulate the Lewis acid strength of the POMOFs via charge regulation, ultimately allowing the POMOFs to display superior catalytic performance in the tandem catalysis of furfural (FAL) to γ-valerolactone (GVL). Among the three catalysts (POMOF-PW, POMOF-PMo and POMOF-SiW), a complete conversion of FAL was achieved, while POMOF-PW exhibited the highest GVL yield (58.1 %) at 160 °C within 23 h. The leaching experiment and structural characterization of the catalyst before and after recycling confirmed the stability of the catalyst structure. The humin originates from the polymerization of furan ring-containing compounds driven by Brønsted acid. The adsorption configuration of the substrate molecules on the catalyst offers a new explanation for the tandem reaction process, i.e. that perpendicular adsorption performs only the first step of the tandem reaction, while the coexistence of perpendicular and horizontal adsorption permits the entire reaction process. This work gives unique insights into the tandem reaction of FAL and can guide the design of efficient tandem reaction catalysts. A synthetic strategy has been developed to construct polyoxometalate-based metal-organic framework (POMOF) with bifunctional Lewis-Brønsted acid sites by chemically confining polyoxometalates (POM) in metal-organic framework (MOF) channels. Confined POM not only endows the catalyst with Brønsted acid sites, but also enhances the acid strength of the catalyst through charge regulation, which finally promotes the catalyst to exhibit excellent catalytic performance in the multi-step cascade catalysis from furfural (FAL) to γ-valerolactone (GVL). This work also provides insight into the origin and driving sites of the by-product humin, as well as the role of the adsorption configuration in the catalytic process. A look into the future of the multi-step tandem reaction of FAL to GVL is presented. [Display omitted] [ABSTRACT FROM AUTHOR]

The transformation of lignocellulosic biomass to platform compounds (γ-valerolactone, GVL) was a significant component in biomass development. Herein, sulfonated Zr-based metal-organic frameworks (MOF-808), a bifunctional heterogeneous catalyst with Lewis and Bronsted acid sites, were prepared to catalyze the one-pot cascade reaction of furfural (FUR) to GVL. The successful modification of the sulfonic group on MOF-808 was substantiated by multiple characterization methods. By adjusting the sulfuric acid concentration to balance the Lewis acid and Bronsted acid sites of the catalyst, S-808–2.37 was confirmed as the preferred catalyst and a 60.4 % GVL yield was achieved with 99.1 % carbon balance under the optimal conditions. Moreover, the 72.8 % GVL yield reached in the 40x magnification experiment also boded well for the catalyst's application potential. The work in this paper opened up new perspectives for the application of MOF-808 porous materials in the field of selective catalytic conversion of biomass involving multi-step reactions. [Display omitted] • Strong interaction between Zr and OH of H 3 BDC led to the formation of strong Lewis acidic/basic sites in the frameworks. • The cooperative role of strong Lewis acidic/basic sites in the S-808–2.37 contributed to the excellent catalytic performance. • This work provided a promising strategy to modulate the acid-base properties of MOF-808 without affecting its structure. [ABSTRACT FROM AUTHOR]

• Zirconium ion-intercalated montmorillonite was synthesized by a facile method. • The amount of Lewis and Bronsted acids could be altered by changing the concentration of zirconium ions. • One-pot cascade conversion of FAL to GVL was achieved under mild conditions. • Over 99% furfural conversion and 50.4% GVL yield were attained. A series of ultrathin metal intercalated montmorillonite (Mont) nanosheet materials were prepared and characterized for the one-pot cascade conversion of furfural (FAL) to obtain γ-valerolactone (γ-GVL). The coordination of the intercalated metal ions and the hydroxyl groups between the montmorillonite layers leads to an increase in the specific surface area and pore volume of the material, which coupled with the acidity of the metal ions themselves improves the catalytic performance of the material. Thus Zr-Mont-0.1 exhibited optimal catalytic performance with 100% conversion of FAL and 50.4% yield of GVL under mild conditions, and more importantly, the catalyst maintained its good catalytic performance after the fourth use. Meanwhile the number of Lewis and Brønsted acid sites in the Zr-Mont catalyst can be varied by adjusting the zirconium ion concentration. The proposed reaction mechanism provides initial insights into the role of metal-functionalized montmorillonite in catalyzing the reaction. In addition, the ten-fold magnification reaction confirmed the potential industrial application of the catalyst. [Display omitted] [ABSTRACT FROM AUTHOR]

A stable and easily separable Fe 3 O 4 -12 nanoparticles exhibited the desired catalytic performance in the catalytic transfer hydrogenation reaction of furfural to furfuryl alcohol with 2-propanol as the hydrogen source. Moreover, a feasible flowchart from xylose to FOL was designed. Utilizing the process can realize the regeneration of biomass resources, the reuse and recycling of catalysts and solvents, and minimize the amount of solvents and pollutant emissions. • Magnetic Fe 3 O 4 -12 nanoparticles exhibited excellent catalytic performance for the CTH reaction of FAL to FOL. • A feasible flowchart from xylose to FOL was designed, which can realize the valorization of biomass resources. • Fe 3 O 4 -12 nanoparticles have good recyclability and universality for different carbonyl compounds. Magnetic Fe 3 O 4 -12 nanoparticles, an easily separable heterogeneous catalyst, exhibits high catalytic performance in the catalytic transfer hydrogenation (CTH) reaction of biomass-derived furfural (FAL) to furfuryl alcohol (FOL) with 2-propanol (2-PrOH) as the hydrogen source (90.1 % FOL yield at 160 °C for 5 h). Comparing Fe 3 O 4 nanoparticles with different particle sizes found that the smaller the nanoparticles, the larger the BET surface area, pore volume and pore diameter, resulting in more acid-base active sites through BET, SEM, TEM, NH 3 -/CO 2 -TPD and other characterizations. Moreover, a scaled-up CTH experiment of FAL and a stepwise reaction from xylose to FOL verified that the catalytic system has great industrial application prospects. A feasible flowchart of the chemical process from xylose to FOL was designed, which can realize the regeneration of biomass resources (xylose derived from corncob), the reuse and recycling of catalysts and solvents, and minimize the amount of solvents and pollutant emissions. [ABSTRACT FROM AUTHOR]