The conversion of residual biomass from fruit seeds into biochar can be achieved using MgCl2 as an activating agent and calcining at 700 °C. The resulting MgO-biochars were employed in the aldol condensation reaction between furfural and acetone. This reaction is essential as the first step in the obtention of biofuels derived from biomass. The biochars were characterized through various physicochemical techniques, revealing that the presence of MgO nanoparticles deposited on the carbon surface modifies the structural and acidic-basic properties of the carbonaceous materials with a graphitic structure. The biochar with a surface content of MgO of 0.34% w/w enables the achievement of 100% of selectivity towards 4-(2-furanyl)-3-buten-2-one (I) with quantitative conversions under optimized conditions. This property highlights the potential of using this type of biochar, commonly used for CO2 capture, as a versatile acidic-basic catalyst, thereby introducing a novel approach to sustainable chemistry.

Small molecules and polymers with conjugated structures can be used as organic optoelectronic materials. These molecules have conventionally been synthesized by cross-coupling reactions; however, in recent years, direct functionalization of C-H bonds has been used to synthesize organic optoelectronic materials. Representative reactions include direct arylation reactions (C-H/C-X couplings, with X being halogen or pseudo-halogen) and cross-dehydrogenative coupling (C-H/C-H cross-coupling) reactions. Although these reactions are convenient for short-step synthesis, they require regioselectivity in the C-H bonds and suppression of undesired homo-coupling side reactions. This review introduces examples of the synthesis of organic optoelectronic materials using two types of direct C-H functionalization reactions. In addition, we summarize our recent activities in the development of direct C-H functionalization reactions using fluorobenzenes as substrates. This review covers the reaction mechanism and material properties of the resulting products.

Many new achievement developments for different industries have their origin in the basic science. Within the last years, this trend is gaining much attention since the interaction between both fields (scientific and industry) is increasing. This article presents some rational materials chemical modifications that were developed by the basic science and were, then, transferred to the productive sector. Conducting hydrophobic coatings for aerospace applications, hydrogels for the oil & gas industry as well as polymers for removal of heavy metal were some of the topics approached in the lab to solve industrial problems. Many times, nature is a great source of inspiration to produce new materials. In this sense, superhydrophobicity and superhydrophilicity (concepts closely related to our everyday life) were the bioinspiration for the development of membranes. These membranes were able to separate hydrocarbons and water, which found application in the treatment of subterranean water for oil & gas industry.

Beyond n=1: This focused review describes 10 π–18 π electrocyclizations reported in the literature. The use of these processes for the synthesis of complex cyclic scaffolds is also briefly described. DFT mechanistic analysis of the reported pericyclic reactions are discussed. It was found that, for some of these reactions, the Woodward-Hoffmann rules for thermal electrocyclizations are not followed.

Abstract

In general, electrocyclizations follow the Woodward-Hoffmann's rules of conservation of orbital symmetry. These rules have been extensively verified in low-order processes, both in thermal and photochemical reactions, up to eight π-electrons. However, when the number of π-electrons in the system increases, some deviations of that general rules can be found. This focused review highlights the main features of reported higher-order electrocyclizations involving 10, 12, 14, 16 and 18 π-electrons. Some of these examples constitute useful intermediates in the synthesis of biologically active compounds. When computational studies were not included in the reported examples, DFT calculations have been performed to be included in this review. Analysis of the respective pericyclic topologies shows the importance of computational tools for understanding the selectivity observed experimentally.

Nucleic acids, universally acknowledged as the essential carriers of genetic information, can be artificially manipulated and assembled into simple, robust, and sensitive biosensors without the assistance of temperature cycling or enzymes. These smart biosensors based on entropy-driven reaction, hybridization chain reaction, catalytic hairpin assembly, and DNAzyme, as well as their extensive applications are summarized in this Review.

Abstract

The isothermal enzyme-free nucleic acid amplification method plays an indispensable role in biosensing by virtue of its simple, robust, and highly efficient properties without the assistance of temperature cycling or/and enzymatic biocatalysis. Up to now, enzyme-free nucleic acid amplification has been extensively utilized for biological assays and has achieved the highly sensitive detection of various biological targets, including DNAs, RNAs, small molecules, proteins, and even cells. In this Review, the mechanisms of entropy-driven reaction, hybridization chain reaction, catalytic hairpin assembly and DNAzyme are concisely described and their recent application as biosensors is comprehensively summarized. Furthermore, the current problems and the developments of these DNA circuits are also discussed.

Supported catalysts: Air-calcination of a silica supported palladium complex provides more active catalyst for dehydrogenation and reduction reactions compared to those obtained by its pyrolysis under hydrogen or argon atmosphere.

Abstract

Generating highly dispersed metal NPs of the desired size on surfaces such as porous silica is challenging due to wettability issues. Here, we report highly active and well-dispersed Pd incorporated mesoporous MCM-41 (Pd@MCM) using a facile impregnation via a molecular approach based on hydrogen bonding interaction of a palladium β-diketone complex with surface silanol groups of mesoporous silica. Controlled thermal treatment of so obtained materials in air, argon, and hydrogen provided the catalysts characterized by electron microscopy, nitrogen physisorption, X-ray diffraction and spectroscopy. Gratifyingly, our catalyst provided the lowest ever activation energy (14.3 kJ/mol) reported in literature for dehydrogenation of NaBH₄. Moreover, the rate constant (7×10⁻³ s⁻¹) for the reduction of 4-nitrophenol outperformed the activity of commercial Pd/C (4×10⁻³ s⁻¹) and Pd/Al₂O₃ (5×10⁻³ s⁻¹) catalysts.

S₁/ICT state dynamics of 8’-apo-β-carotenal in acetonitrile during bulk electrolysis are examined in this work. Transient absorption spectra show decrease of ICT band during bulk electrolysis, accompanied by increase of S₁/ICT state lifetime from 8 ps to 13 ps.

Abstract

This work examines the influence of applied external voltage in bulk electrolysis on the excited-state properties of 8′-apo-β-carotenal in acetonitrile by steady-state and ultrafast time-resolved absorption spectroscopy. The data collected under bulk electrolysis were compared with those taken without applied voltage. The steady-state measurements showed that although intensity of the S₀-S₂ absorption band varies with the applied voltage, the spectral position remain nearly constant. Comparison of transient absorption spectra shows that the magnitude of the ICT-like band decreases during the experiment under applied voltage condition, and is associated with a prolongation of the S₁/ICT-like lifetime from 8 ps to 13 ps. Furthermore, switching off the applied voltage resulted in returning to no-voltage data within about 30 min. Our results show that the amplitude of the signal associated with the ICT state can be tuned by applying an external voltage.

Highly water-soluble acyclic cucurbiturils (ACBs) can include cationic drugs to lead to efficient masking of their bitter taste. Two-bottle preference (TBP) tests on mice show that all ACBs are tasteless to mammals. ACBs are discovered to mask the bitterness of berberine and denatonium benzoate, but not quinine hydrochloride, due to different binding modes.

Abstract

New acyclic cucurbit[n]urils (ACBs) with eight carboxylate groups were synthesized. These hosts are highly soluble in water, and can form stable inclusion complexes with cationic bitter compounds. ACBs are confirmed to be non-toxic and biocompatible. Two-bottle preference (TBP) tests on mice show that all ACBs are tasteless to mammals. ACBs are discovered to mask the bitterness of berberine and denatonium benzoate, but not quinine hydrochloride, due to different binding modes.

Different −C≡C− and −C=C− adsorbed species were observed on the supports and catalysts surface using in situ DRIFT analysis: The species are responsible for the activity and high selectivity during the hydrogenation reaction. The role of the supports and electronic properties of Ag nanoparticles improve the H₂ dissociative chemisorption; promoting the high selectivity and the catalytic performance.

Abstract

The catalytic performance of nanoparticles (NPs) of Ag anchored on different supports was evaluated during the selective hydrogenation of 1-pentyne and the purification of a mixture of 1-pentene/1-pentyne (70/30 vol %). The catalysts were identified: Ag/Al (Ag supported on ɣ-Al₂O₃), Ag/Al−Mg (Ag supported on ɣ-Al₂O₃ modified with Mg), Ag/Ca (Ag supported on CaCO₃) and Ag/RX3 (Ag supported on activated carbon-type: RX3). In addition, in situ DRIFTS analysis of 1-pentyne adsorption on each support, catalyst, and 1-pentyne hydrogenation were investigated. The results showed that the synthesized catalysts were active and very selective (≥85 %) for obtaining the desired product (1-pentene). Different adsorbed species (−C≡C− and −C=C−) were observed on the supports and catalysts surface using in situ DRIFT analysis, which can be correlated to the activity and high selectivity reached. The role of the supports and electronic properties over Ag improve the H₂ dissociative chemisorption during the hydrogenation reactions; promoting the selectivity and the high catalytic performance. Ag/Al and Ag/Al−Mg were the most active catalysts. This was due to the synergism between the active Ag/Ag⁺ species and the supports (electronic effects). The results show that Ag/Al and Ag/Al−Mg catalysts have favorable properties and are promising for the alkyne hydrogenation and olefin purification reactions.

Cyclic carbonates have received significant interests for uses as reagents, solvents, and monomers. The coupling reaction of epoxides with carbon dioxide (CO2) to produce cyclic carbonate is an attractive route which can significantly reduce greenhouse gas emissions and environmental hazards. Herein, a series of five indium chloride complexes supported by inden Schiff-base ligands were reported along with four X-ray crystal structures. The constrained five-membered rings were added to the ligands to enhance the coordination of epoxides to the In metal. From the catalyst screening, In inden complex having tert-butyl substituents and propylene backbone in combination with tetrabutylammonium bromide (TBAB) exhibited the highest catalytic activity (TON up to 1017) for propylene oxide/CO2 coupling reaction with >99% selectivity for cyclic carbonate under solvent-free conditions. In addition, the catalyst was shown to be active at atmospheric pressure of CO2 at room temperature. The catalyst system can be applied to various internal and terminal epoxide substrates to exclusively produce the corresponding cyclic carbonates.