Volume 6 Issue 7, July 2023

Photocatalytic hydrogen peroxide formation is an advancing field with various approaches motivated by the promise of a green oxidant and energy carrier for a sustainable future. An assessment on quantification methods, sacrificial agents and best practices is provided to avoid false positives and support progress in the field.

Ethylene glycol is traditionally manufactured through energy-intensive thermocatalytic processes. Now, in a marked advance, a cascade catalytic system using electrochemically synthesized H₂O₂ for ethylene oxidation has been introduced. This strategy represents a benchmark for sustainable chemical manufacturing.

Directed evolution has been extensively used to develop enzymes with enhanced properties, but there are limited examples of diverting key intermediates in catalytic cycles down alternative pathways. Now, a cytochrome P450 variant with promiscuous catalytic activity has been repurposed into a ketone synthase for the catalytic aerobic oxidation of internal alkenes to ketones.

Catalytic pyrolysis is a promising process for the valorization of biomass and plastic waste, although several aspects related to its practical utilization remain unexplored. This Perspective revisits the salient features of catalytic pyrolysis, identifying a roadmap to advance the application of this technology at commercial scale.

Organic semiconductors have potential for application as photocatalysts, but their efficiency is limited by recombination of charge carriers before they can reach the surface. Here hydrogen-bonded organic frameworks with designed micropores decrease the exciton transfer path to improve charge utilization in photocatalytic H₂ evolution.

Ethylene glycol is commercially produced from ethylene under energy-intensive thermocatalytic conditions. Now a cascade electrochemical heterogeneous system can produce ethylene glycol from ethylene or from CO₂ under ambient conditions using electrocatalytically generated H₂O₂ and an integrated catalyst/solid-acid composite.

Kinetic measurements often involve complex processes, and deconvoluting them to derive active-site chemistry becomes challenging. Now experimental kinetic measurements, density functional theory calculations and microkinetic modelling are combined to provide detailed mechanistic understanding of elementary reactions for ethylene hydrogenation on Pd–Zn γ-brass with isolated active sites.

The direct regioselective oxidation of internal alkenes to ketones poses an important synthetic challenge. Now, directed evolution of a cytochrome P450 enzyme affords a ketone synthase that can efficiently oxidize internal arylalkenes directly to ketones with high chemo- and regioselectivity.

Reversibly modulating the structure of supported metals in response to dynamic working conditions is a desirable feature for catalysts. Now, the reversible transformation between single atoms and subnanometre clusters of Pd on CeO₂ is demonstrated during automotive exhaust aftertreatment, achieving high methane oxidation activity and stability.

Controlling the stereoselectivity in free-radical-mediated reactions is challenging. Now, a metalloredox biocatalysis strategy is reported that uses engineered cytochrome P450 enzymes for the unnatural asymmetric radical cyclization of α-haloesters to arenes.

Cyclases that are able to build medium-sized rings are rare and mechanistic insights are sparse. Now, computational and experimental studies reveal how SoBcmB enables the construction of an eight-membered O-heterocycle over the intrinsically more favourable five-membered tetrahydrofuran in bicyclomycin biosynthesis.