Developing sulfonic-acid-supported catalysts with superacidity and hydrophobicity is of great importance for many acid-catalyzed reactions where H 2 O is generated. Herein, a novel hydrophobic superacidic biochar is first reported via a diazo grafting method using halogen-substituted aminobenzenesulfonic acids and 4-tert-butylaniline as sulfonating and hydrophobic reagents, respectively. The resultant biochar has a high Brunauer−Emmett− Teller (BET) surface area (400−700 m 2 •g −1 ), acid concentration (up to 1.5 mmol•g −1 ), and H 2 O contact angle (above 134°). The synergistic effect of superacidity and hydrophobicity greatly improves the catalytic alkylation reactions of 4-ethylphenol-phenylmethanol and 2-methylfuran-cyclic ketones for the synthesis of renewable high-density fuels. The hydrophobic superacidic biochar shows higher catalytic conversion and selectivity than those of its counterparts without hydrophobicity or superacidity. Meanwhile, it is also far superior to commercial Amberlyst-15 and the traditional sulfonated biochar. Finally, the catalyst is stable without obvious activity reduction after cycling.

The production of 5-hydroxymethylfurfural (HMF) by the acid-catalyzed dehydration of fructose is of great significance for the comprehensive utilization of biomass resources. However, the water generated in situ not only leads to the deactivation of the active sites but also triggers the rehydration side reaction of HMF, resulting in an unsatisfactory catalytic activity and selectivity. Herein, for the first time, metal–organic frameworks (MOFs) with strong Brønsted acidity and hydrophobicity were prepared by grafting arenesulfonic acid by a diazo method. These functionalized MOFs have a large specific surface area of 1700–2600 m2/g, a high acid density of over 1.2 mmol/g, and a strong hydrophobicity with an H2O contact angle of greater than 125°. Compared with the MOF directly functionalized with sulfonic acid, the arenesulfonic acid-functionalized MOFs, which have a stronger hydrophobicity, exhibit higher activity and selectivity (up to 98.3% yield) in the transformation of fructose to HMF. Meanwhile, these arenesulfonic acid-functionalized MOFs also exhibit an excellent HMF yield for glucose and inulin reactions via the cooperative catalysis of Lewis and Brønsted acids. Furthermore, the good activity and stability of the functionalized MOFs can be maintained after recycling for five runs. The successful preparation of hydrophobic acidic MOFs provides not only an efficient catalytic system for the synthesis of HMF but also a novel, efficient route for MOF functionalization.

No abstract

Separation of a gas mixture achieved by the vacuum swing adsorption (VSA) technology is considered as an efficient and energy-saving method for Xe/Kr mixtures, but developing efficient and stable adsorbents remains challenging. Herein, we report an ultramicroporous metal–organic framework, namely, MIL-120 with a suitable pore size (5.4 Å × 4.7 Å), rich hydroxyl-decorated sites, and ultrahigh stability, which is capable of highly selective adsorption of xenon from krypton. Specifically, MIL-120 exhibits an excellent adsorption capacity of Xe up to 1.15 and 1.99 mmol g–1 at 298 K under 0.1 bar and 1 bar, respectively, and outstanding ideal adsorbed solution theory selectivity of 9.6 for the Xe/Kr mixture, which is comparable to those of benchmark porous materials. The isosteric heat of adsorption (Q st) and density functional theory calculations further confirm the stronger interaction of the adsorbent toward Xe than Kr. Furthermore, the cycling breakthrough experiments, hydrothermal and acid-based stability tests, and VSA assessment comprehensively demonstrate that the MIL-120 is an efficient and potent adsorbent for Xe/Kr separation under industrial conditions.

Bi-functional mesoporsous silica adsorbents, functionalized via the introduction of chelating agents (mercaptopropyl and aminopropyl groups) were prepared to adsorb Co2+ and Mn2+ in dilute solutions. The molar ratio of MPTMS/APTMS in grafting process seemed to have great effected on the mesostructure of adsorbents, and the appropriate value was considered to be 2/1. The modified silica gels at that ratio showed well-ordered property as well as its high infinity of the two metal ions. The pseudo-second-order equation was applied to describe the adsorption kinetics. And the influence of interferential ions Ca2+ and Mg2+ was also studied.