Anders Thapper

We developed N‐doped carbon quantum dots (N‐CQDs) as both photocathode modifiers and electrolytes for self‐powered portable photoelectrochemical (PEC) cells to generate electricity under visible‐light illumination. Using betaine‐type Meldonium precursor, and either ethylenediamine, N,N ‐dimethylformamide or NH ₃ ·H ₂ O as a nitrogen source deliver three different N‐CQDs featuring both surface‐negatively‐charged and positively‐charged groups. Due to structural‐directing template functionality of ethylenediamine, N‐CQDs(en) incorporates the highest pyridinic‐N content, which facilitates the charge conductivity and fine‐regulates the reaction selectivity within Csp ² ‐frameworks. As semiconductor‐coatings electrodeposited on Cu ₂ O, N‐CQDs(en) integrate with Cu ₂ O into heterojunctions (N‐CQDs(en)/Cu ₂ O) to improve charge separation and promote 4e ⁻ oxygen‐reduction into water. Importantly, encapsulating an aqueous solution containing N‐CQDs(en) in a gelatin/sodium L‐pyroglutamate‐derived conductor gives a quasi‐solid‐state electrolyte that facilitates the charge migration, improving the electrodes‐electrolytes interfacial incompatibility, while also possibly helping to in situ complement active sites on the modified photocathode. Coupled with a FeNiOOH/FeN‐decorated BiVO ₄ photoanode, enabling the efficient 4e ⁻ water oxidation, the complete system establishes a self‐sustaining H ₂ O–O ₂ –H ₂ O cycle. The resulting PEC cell shows impressive electricity output for over 120 h under irradiation, enough to power some small electronics. Unlike conventional photovoltaics, this cell is moisture‐tolerant, oxidation‐resistant and concurrently harnesses light and chemical energy, presenting a new paradigm for next‐generation light‐to‐electricity conversion.

Molecules capable of reversibly transitioning between istinct states in response to multiple stimuli are highly sought after for responsive materials, enabling precise control over electronic structure at the molecular level. While overcrowded alkene (OCA) diradicaloids have shown promise in this context, research has largely centered on carbon-based systems, leaving main-group alternatives underexplored. Herein, we present the synthesis of an air stable, phosphaalkene substituted hybrid OCA diradicaloid, obtained by replacing one exocyclic C=C bond of an anthraquinodimethane core with a low-valent phosphaalkene unit (–C=P–Mes*, Mes*= 2,4,6-tri-tert butylphenyl) and appending a fluorenyl group at the opposite terminus. This unique molecular framework enables distinct responses to external stimuli, as demonstrated by comprehensive spectroscopic analysis and supported by theoretical studies. The molecule undergoes a temperature-induced, reversible conformational change from a folded quinoidal to a twisted diradicaloid state via rotation of the fluorenyl unit about the central overcrowded alkene bond. Furthermore, reversible Lewis acid–base interactions at the phosphorus center dynamically modulate the diradical character, illustrating a rare example of chemical control in a main-group-based OCA diradicaloid. These findings open new avenues for the design of main-group diradicaloids with multi-stimulus responsiveness.

Constructing aggregation‐resistant, full‐Quantum Dot (QD)‐based S‐scheme heterostructures is critical yet challenging for the enhanced photocatalysis. Herein, a charge‐directed and defect‐induced strategy is presented to fabricate a novel full QD‐based heterostructure CdS&CQD and its photocatalytic feature. The CdS&CQD is assembled from a negatively‐charged and sulfur‐vacancy‐rich CdS QD, and a both positively‐charged‐groups and thiophene‐moieties functionalized carbon‐quantum‐dot (CQD). Electrostatic interaction ensures the close contact between CdS and CQD, suppressing the homo‐QD aggregation. Assisted by thiophene groups on CQD and sulfur‐vacancies on CdS, they act as complementary “jigsaw puzzle” motifs, guiding the formation of a chemically bonded Cd–S interface. This process results in a colloidally stable full‐QD‐based CdS&CQD with the maximal active site exposure. The atomic‐level connectivity in CdS&CQD established a robust internal electric field, driving S‐scheme charge transfer with long‐lived excitons and enhanced redox capacity for the photocatalyst. Consequently, CdS&CQD efficiently activates the inert biomass‐derived furfural and CO ₂ , enabling synergistic furfural aldol‐condensation with acetone to yield a high‐value‐added product, integrated with the selective CO ₂ ‐to‐CO reduction. CdS&CQD also displays recycling stability as well as the activity under outdoor sunlight irradiation. This work provides fundamental significance for designing and constructing full‐QDs‐based heterostructures with tailored photocatalytic redox‐capabilities.

Switchable self‐driven photoelectrochemical (PEC) devices are developed to boost H ₂ O ₂ or electricity generation under visible‐light illumination, in which p‐n type carbon quantum dots (N‐CQDs) is applied as conceptually‐new “semiconductor electrolytes”. The N‐CQDs contains N‐dopants, and both negatively‐ and positively‐charged surface groups. This allows N‐CQDs to act as the electrolyte and to interact with both a BiVO ₄ photoanode and a Cu ₂ O photocathode. In a two‐compartment cell with a separating membrane, N‐CQDs can dynamically form p‐n heterojunctions with the photoanode or the photocathode, facilitating charge separation. In this setup, the fine‐tuned electronic structure of N‐CQDs promotes the two‐electron reactions with water or O ₂ to produce H ₂ O ₂ , achieving a rate of 28 µ m min ⁻¹ and Faradic efficiency exceeding 80%. Switching into a one‐compartment cell, N‐CQDs promotes four‐electron charge transfer and stabilizes the photoelectrodes, giving electricity output for over 120 h. This control over electron transfer, selectivity, and durability cannot be achieved using traditional electrolytes.

Understanding the structure of Ru(V)-oxo species is crucial for designing novel catalysts for sustainable energy applications, such as water splitting for green hydrogen production. This study reports the EPR detection of a Ru(V)-oxo intermediate stabilized by terpyridine and phenanthroline carboxylate ligands. The interaction between the carboxylate group and the ruthenium center, along with PCET-dependent hemilability under oxidative conditions, plays a critical role in achieving the high-valent state. Subtle changes in the coordination environment around the central metal also proved to be essential. Low-temperature NMR, high-resolution mass spectrometry, UV–Vis spectroscopy, and density functional theory calculations support these findings.

The reduction of stable trivalent lanthanide species (Ln(III)) by the excited states of organic chromophores is the basis of photocatalytic divalent lanthanide-mediated reduction reactions. While indirect evidence of the photochemical formation of the reactive Ln(II) species is abundant, direct spectroscopic evidence of their presence is scarce. Here, nine chromophores with absorptions covering the near UV and visible ranges were systematically investigated in the presence of Ln(III) ions to evaluate their ability to reduce Eu(III) upon excitation with visible light to the catalytically active Eu(II) species. Irradiated mixtures of Eu(III) and the chromophores were characterized using UV-vis absorption and emission and EPR spectroscopy. Several of the chromophore-Eu(III) combinations were competent photocatalysts in the presence of N,N-diisopropylethylamine or Zn terminal reductants. These results demonstrate that a variety of visible-absorbing chromophores can efficiently generate reactive Eu(II) from Eu(III) to catalyze Ln(II)-mediated reduction reactions.

Commercially available coumarin 343 in combination with reducible Sm(III) ions catalyzed divalent lanthanide-mediated C═O, C-halogen, P-Cl, and N═N reductions at ambient temperature in aqueous solvent mixtures. The catalyst absorbs visible light efficiently. The active divalent species is formed by photoinduced electron transfer from coumarin 343 to the stable trivalent precursor, and the coumarin could be regenerated by strictly 1 equiv of ascorbic acid.

The stepwise reduction of the highly contorted truxene‐based triphosphaalkene 1 using KC ₈ led to the isolation of mono‐, di‐, and tri‐anionic species. The solid‐state molecular structures of mono‐ and diradical anionic species were elucidated by single crystal X‐ray diffractions, revealing elongated P−C bonds and a pronounced “indene” aromatization compared to the parent system. All three radical species displayed distinct Electron Paramagnetic Resonance (EPR) spectra, providing compelling evidence for the open‐shell electronic configuration of both the diradical and triradical species—an observation unprecedented in any previously reported phosphorous‐based anionic polyradicals. Mulliken spin density calculations revealed a dominant localization of radical spin on a single phosphorous atom in the monoanion. In the dianion, spin localization is observed on two phosphorous atoms (~34 % each), with a minor contribution from the third phosphorous (0.13 %), while the trianion demonstrates a uniform distribution of spin density (~30 %) across each phosphorous atom.