We synthesized CuAlS 2 /ZnS quantum dots (QDs) composed of biocompatible, earth-abundant elements that can reduce salts of carbon dioxide under visible light. The use of an asymmetric morphology at a type-II CuAlS 2 /ZnS heterointerface balances multiple requirements of a photoredox agent by providing a low optical bandgap (∼1.5 eV), a large optical cross section (>10 −16 cm 2 above 1.8 eV), spatial proximity of both semiconductor components to the surface, as well as photochemical stability. CuAlS 2 /ZnS QDs thus have an unprecedented photochemical activity in terms of reducing carbon dioxide in the form of aqueous sodium bicarbonate under visible light, without the need for a cocatalyst, promoter, or sacrificial reagent while maintaining large turnover numbers in excess of 7 × 10 4 per QD. Devices based on these QDs exhibit energy conversion efficiencies as high as 20.2 ± 0.2%. These observations are rationalized through our spectroscopic studies that show short 550 fs electron dwell times in these structures. The high energy efficiency and the environmentally friendly composition of these materials suggest a future role in solar light harvesting.

The necessity of well-tuned reactivity for successful controlled polymer synthesis often comes with the price of limited monomer substrate scope. We demonstrate here the on-demand interconversion between living radical and cationic polymerization using two orthogonal stimuli and a dual responsive single catalyst. The dual photo- and electrochemical reactivity of 10-phenylphenothiazine catalyst provides control of the polymer’s molar mass and composition by orthogonally activating the common dormant species toward two distinct chemical routes. This enables the synthesis of copolymer chains that consist of radically and cationically polymerized segments where the length of each block is controlled by the duration of the stimulus exposure. By alternating the application of photochemical and electrochemical stimuli, the on-demand incorporation of acrylates and vinyl ethers is achieved without compromising the end-group fidelity or dispersity of the formed polymer. The results provide a proof-of-concept for the ability to substantially extend substrate scope for block copolymer synthesis under mild, metal-free conditions through the use of a single, dual reactive catalyst.

Reaction of MBr2 with 3 equiv of [K(18-crown-6)][O2N2CPh3] generates the trityl diazeniumdiolate complexes [K(18-crown-6)][M(O2N2CPh3)3] (M = Co, 2; Fe, 3) in good yields. Irradiation of 2 and 3 using 371 nm light led to NO formation in 10 and 1% yields (calculated assuming a maximum of 6 equiv of NO produced per complex), respectively. N2O was also formed during the photolysis of 2, in 63% yield, whereas photolysis of 3 led to the formation of N2O, as well as Ph3CN(H)OCPh3, in 37 and 5% yields, respectively. These products are indicative of diazeniumdiolate fragmentation via both C–N and N–N bond cleavage pathways. In contrast, oxidation of complexes 2 and 3 with 1.2 equiv of [Ag(MeCN)4][PF6] led to N2O formation but no NO formation, suggesting that diazeniumdiolate fragmentation occurs exclusively via C–N bond cleavage under these conditions. While the photolytic yields of NO are modest, they represent a 10- to 100-fold increase compared to the previously reported Zn congener, suggesting that the presence of a redox-active metal center favors NO formation upon trityl diazeniumdiolate fragmentation.

Ion-selective membranes are an essential, yet expensive fixture in redox flow batteries, preventing charge carrier crossover between the two half-cells. This work demonstrates the viability of replacing these membranes with an electrolyte solution that is mutually immiscible with the two half-cell solutions, eliminating the direct anolyte–catholyte interface that leads to self-discharge in existing biphasic cells. We developed a simple dichloromethane (DCM)/water model system consisting of charge carriers in the organic phase connected by an immiscible aqueous electrolyte sharing a common anion (PF6 –) with the DCM phase. This “split biphasic” model cell maintained high Coulombic efficiencies (>99%) and capacity retention (∼95%) over a period of 24 h for fully charged cells. Lastly, we demonstrated the performance of this model system at scale in high-surface-area cells while retaining rapid charge–discharge at a rate of 1C.

Coordination induced bond weakening (CIBW) leads to facile PCET at various E–H bonds.