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The Cover Feature illustrates the evolution of supported metal catalysts from conventional bulk and nanoparticle catalysts to single-atom catalysts (SACs), and the race to develop SACs with richer active sites for the future era of single atom catalysis. In their Review, W. Sangkhun, J. Ponchai et al. demonstrated the research efforts to increase the density of active sites (metal loading) of SACs from <0.1 wt% in the pioneer works to >25 wt% in the recently reported one. The successful preparation strategies to achieve high metal-loading SACs are highlighted, and the outlooks to further improve the quantity and quality of active sites in SACs are pointed out. More information can be found in the Review by W. Sangkhun, J. Ponchai et al.

Pining for catechol: A catalytic route is developed to synthesize bio-renewable catechol from pinewood-derived lignin-first monomers. The two-step process consists of O-demethylation of 4-n-propylguaiacol over acidic beta zeolites in hot pressurized liquid water, delivering 4-n-propylcatechol, and gas-phase C-dealkylation of 4-propylcatechol providing catechol and propylene over acidic ZSM-5 zeolites in the presence of water.

Abstract

A catalytic route is developed to synthesize bio-renewable catechol from softwood-derived lignin-first monomers. This process concept consists of two steps: 1) O-demethylation of 4-n-propylguaiacol (4-PG) over acidic beta zeolites in hot pressurized liquid water delivering 4-n-propylcatechol (4-PC); 2) gas-phase C-dealkylation of 4-PC providing catechol and propylene over acidic ZSM-5 zeolites in the presence of water. With large pore sized beta-19 zeolite as catalyst, 4-PC is formed with more than 93 % selectivity at nearly full conversion of 4-PG. The acid-catalyzed C-dealkylation over ZSM-5 zeolite with medium pore size gives a catechol yield of 75 %. Overall, around 70 % catechol yield is obtained from pure 4-PG, or 56 % when starting from crude 4-PG monomers obtained from softwood by lignin-first RCF biorefinery. The selective cleavage of functional groups from biobased platform molecules through a green and sustainable process highlights the potential to shift feedstock from fossil oil to biomass, providing drop ins for the chemicals industry.

Nature Chemistry, Published online: 13 December 2021; doi:10.1038/s41557-021-00836-6

The efficient utilization and recycling of carbon resources, which contain mainly the elements C, H, and O, is an effective way to minimize CO₂ emission. In this Minireview, green carbon science is discussed in combination with related fields, including petroleum refining and the production of liquid fuels, chemicals, and materials from coal, methane, CO₂, biomass, and waste plastics.

Abstract

Green carbon science is defined as the “study and optimization of the transformation of carbon-containing compounds and the relevant processes involved in the entire carbon cycle from carbon resource processing, carbon energy utilization, CO₂ fixation, and carbon recycling to utilize carbon resources efficiently and minimize the net CO₂ emission.”^[1] Green carbon science is related closely to carbon neutrality, and relevant fields have developed quickly in the last decade. In this Minireview, we propose the concept of carbon energy index, and the recent progress in petroleum refining, and the production of liquid fuels, chemicals, and materials using coal, methane, CO₂, biomass, and waste plastics is highlighted in combination with green carbon science. An outlook for these important fields is provided in the final section.

Nature, Published online: 13 December 2021; doi:10.1038/d41586-021-03659-0

Synthesis
DOI: 10.1055/a-1671-0085

Sulfinic acids and their salts are a useful source of sulfur-containing structures. Photocatalysis of these compounds with visible light enables to achieve various transformations under mild conditions. This review summarizes visible-light-induced reactions of sulfinic acids and their salts. It is organized by reaction type and brief discussions on plausible reaction mechanisms for typical transformations are presented.1 Introduction2 Sulfonylation Reactions2.1 Sulfonylation of Alkenes2.2 Sulfonylation of Alkynes2.3 Sulfonylation of Arenes2.4 sp3 C–H Functionalization3 Desulfonylation Reactions4 Sulfenylation Reactions4.1 Sulfenylation of Heteroarenes4.2 Sulfenylation of Carbonyl Chlorides5 Conclusions
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

Article in Thieme eJournals:
Table of contents  |  Abstract  |  Full text

Fe/N/C single-atom catalysts are prepared from iron complex precursors containing 5,6,7,8-tetraphenyl-1,12-diazatriphenylene ligands with two bromo substituents by one-step pyrolysis. The iron complex precursors were efficiently converted to atomically dispersed Fe−N₄ active sites without generating less active iron aggregates during pyrolysis. The Fe−N₄ active sites were identified by STEM-EELS observations and in situ electrochemical Fe K edge X-ray absorption spectroscopic measurements. The Fe/N/C catalysts show high catalytic activity toward oxygen reduction reaction.

Abstract

Fe/N/C single-atom catalysts containing Fe−N _x sites prepared by pyrolysis are promising cathode materials for fuel cells and metal-air batteries due to their high oxygen reduction reaction (ORR) activities. We have developed iron complexes containing N2- or N3-chelating coordination structures with preorganized aromatic rings in a 1,12-diazatriphenylene framework tethering bromo substituents as precursors to precisely construct Fe−N₄ sites in an Fe/N/C catalyst. One-step pyrolysis of the iron complex with carbon black forms atomically dispersed Fe−N₄ sites without iron aggregates. X-ray absorption spectroscopy (XAS) and electrochemical measurements revealed that the iron complex with N3-coordination is more effectively converted to Fe−N₄ sites catalyzing ORR with a TOF value of 0.21 e site⁻¹ s⁻¹ at 0.8 V vs. RHE. This indicates that the formation of Fe−N₄ sites is controlled by precise tuning of the chemical structure of the iron complex precursor.