Insights into Shape Selectivity and Acidity Control in NiO-Loaded Mesoporous SBA-15 Nanoreactors for Catalytic Conversion of Cellulose to 5‑Hydroxymethylfurfural

Facilitated isomerization of cellulose hydrolysis intermediate glucose without unexpected byproducts, which is the rate-determining step in the production of high-value-added biofuels, enables the efficient production of 5-hydroxymethylfurfural (5-HMF) from cellulose. In this work, considering the essential role of the acidity control and shape selectivity of a zeolite catalyst, a NiO-loaded mesoporous NiO/poly(vinyl pyrrolidone) (PVP)-phosphotungstic acid (HPA)@SBA-15 nanoreactor was prepared. This SBA-15 nanoreactor with a pore size of 5.47 nm reduced the concentration of byproducts formic acid (FA) and levulinic acid (LA) through shape selection for intermediates. Well-defined NiO nanoparticles (Ni-to-carrier mass ratio was 1:1) provided the NiO/PVP-HPA@SBA-15 nanoreactor a high Lewis acidity of 99.29 μmol g–1 for glucose catalytic isomerization, resulting in an increase in total reducing sugar (TRS) yield by 5 times. Such a nanoreactor remarkably improved the reaction efficiency of 5-HMF production from cellulose (a 5-HMF selectivity of 95.81%) in the 1-butyl-3-methylimidazolium chloride ([BMIM]Cl)/valerolactone (GVL) biphasic system

Seeking Brightness from Nature: J‑Aggregation-Induced Emission in Cellulolytic Enzyme Lignin Nanoparticles

Nanomaterials that show aggregation-induced emission (AIE) have tremendous potential in sensors, bioimaging, phototherapy and organic light-emitting diodes. Although big progress have been achieved in developing AIE nanomaterials and their applications, one downside of most previously described AIE nanomaterials is that they required the complicated organic synthesis of precursor molecules and several preparative steps. Here, a biomass material, cellulolytic enzyme lignin (CEL), was used to prepare AIE nanoparticles (CEL-NPs) by a simple one-step self-assembly method. The J-aggregates were formed in CEL-NPs, which were shown to be the reason for fluorescence emission. The fluorescence of CEL-NPs demonstrated temperature-dependent property and better resistance to photobleaching than that of commercially available 4′,6-diamidino-2-phenylindole (DAPI) dye. The colloidal size of CEL-NPs could be tuned from 80 to 600 nm via changing CEL concentrations and solvent exchange. CEL-NPs showed nice colloidal stability in acidic environment and at low temperature. CEL-NPs and a poly­(vinyl alcohol) (PVA)/CEL-NPs composite film demonstrated good fluorescent responses to formaldehyde (FA) solution and vapor, respectively. This work opens up new possibilities for preparation of AIE nanomaterials and also provides a new high value-added routing for utilization of CEL

Temperature-Dependent Enantio- and Diastereodivergent Synthesis of Amino Acids with One or Multiple Chiral Centers

A general and facile methodology for temperature-dependent enantiodivergent and diastereodivergent synthesis of amino acids with one or multiple chiral centers was developed. Camphor-based tricyclic iminolactones attack electrophiles from the <i>endo</i> face at low temperature (−78 to −40 °C) and from the <i>exo</i> face at high temperature (−10 to 25 °C)

Preparation of Carbon Dots for Cellular Imaging by the Molecular Aggregation of Cellulolytic Enzyme Lignin

Carbon dots, which are less than 10 nm in diameter, have been widely investigated because of their unique luminescence properties and potential for use in bioimaging. In the present work, natural carbon dots (L-CDs) were obtained by molecular aggregation, using ethanol-extracted cellulolytic enzyme lignin. The whole process for the preparation of L-CDs was green and simple to operate and did not use toxic chemical reagents or harsh conditions. The newly prepared L-CDs emitted multicolor photoluminescence following one- and two-photon excitation. The L-CDs also showed good cellular biocompatibility, which is crucial for biological applications. One- and two-photon cell-imaging studies demonstrated the potential of L-CDs for bioimaging

Efficient Cleavage of Strong Hydrogen Bonds in Cotton by Deep Eutectic Solvents and Facile Fabrication of Cellulose Nanocrystals in High Yields

The content of cellulose in biomass is important for producing nanocellulose in high yields. Cotton fibers containing ultrahigh purity (∼95%) cellulose are ideal feedstock for nanocellulose production. However, the presence of strong hydrogen bonding between the cellulose chains limits the use of cotton fibers for the production of nanocellulose in a facile and mild process. Here, efficient cleavage of the strong hydrogen bonds in cotton and ultrafast fabrication of cellulose nanocrystals (CNCs) with a high yield of 74.2% were first realized through a 3 min microwave-assisted deep eutectic solvent pretreatment and a subsequent high-intensity ultrasonication process. The obtained CNCs had diameters of 3–25 nm, and lengths ranged between 100 and 350 nm. The CNCs also displayed a relative crystallinity of 82%, and the thermal degradation temperature started from 320 °C. The study provides a green and efficient method for the mass production of cotton CNCs, and is expected to contribute to improving the refinery utilization of cotton feedstock

Formal Synthesis of Cephalotaxine

A formal synthesis of cephalotaxine, the parent member of the <i>Cephalotaxus</i> alkaloids, was achieved. It features a practical four-step assembly of the benzazepine-bearing pentacyclic ring system through two alkylation reactions, acidic hydrolysis, and aldolization