An account of the fundamental chemical and engineering principles of solid amine-based CO ₂ adsorbents and their industrial application, with discussion of the relevance of amine chemistry in CO ₂ utilisation technology.

In aqueous solution above pH 2.4 with 4% (vol/vol) CH₃CN, the complex [Ru^II(bda)(isoq)₂] (bda is 2,2′-bipyridine-6,6′-dicarboxylate; isoq is isoquinoline) exists as the open-arm chelate, [Ru^II(CO₂-bpy-CO₂⁻)(isoq)₂(NCCH₃)], as shown by ¹H and ¹³C-NMR, X-ray crystallography, and pH titrations. Rates of water oxidation with the open-arm chelate are remarkably enhanced by added proton acceptor bases, as measured by cyclic voltammetry (CV). In 1.0 M PO₄^3–, the calculated half-time for water oxidation is ∼7 μs. The key to the rate accelerations with added bases is direct involvement of the buffer base in either atom–proton transfer (APT) or concerted electron–proton transfer (EPT) pathways. Significance Development of rapid, robust water oxidation catalysts remains an essential element in solar water splitting by artificial photosynthesis. We report here dramatic rate enhancements with added buffer bases for a robust Ru(II) polypyridyl catalyst with a calculated half-time for water oxidation of ∼7 μs in 1.0 M phosphate. The results of detailed kinetic studies provide insight into the water oxidation mechanism and an important role for added buffer bases in accelerating water oxidation by concerted atom–proton transfer.

The structures and properties of the homoleptic copper(I) complexes [Cu(1)₂][PF₆] and [Cu(2)₂][PF₆] (1 = 6,6′-dimethyl-2,2′-bipyridine, 2 = 6,6′-bis{2-[4-(N,N′-diphenylamino)phenyl]ethenyl}-2,2′-bipyridine) are compared, and a strategy of ligand exchange in solution has been used to prepare eight TiO₂ surface-bound heteroleptic complexes incorporating ligands with bpy metal-binding domains and carboxylate or phosphonate anchoring groups. The presence of the extended π-system in 2 significantly improves dye performance, and the most efficient sensitizers are those with phosphonate or phenyl-4-carboxylate anchoring units; a combination of [Cu(2)₂]⁺ with the phosphonate anchoring ligand gives a very promising performance (η = 2.35% compared to 7.29% for standard dye N719 under the same conditions). The high-energy bands in the electronic absorption spectrum of [Cu(2)₂]⁺ which arise from ligand-based transitions dominate the spectrum, whereas that of [Cu(1)₂]⁺ exhibits both MLCT and ligand π* ← π bands. Both [Cu(1)₂][PF₆] and [Cu(2)₂][PF₆] are redox active; while the former exhibits both copper-centred and ligand-based processes, [Cu(2)₂][PF₆] shows only ligand-based reductions. Results of TD-DFT calculations support these experimental data. They predict an electronic absorption spectrum for [Cu(1)₂]⁺ with an MLCT band and high-energy ligand-based transitions, and a spectrum for [Cu(2)₂]⁺ comprising transitions involving mainly contributions from orbitals with ligand 2 character. We have assessed the effects of the atomic orbital basis set on the calculated absorption spectrum of [Cu(1)₂]⁺ and show that a realistic spectrum is obtained by using a 6-311++G** basis set on all atoms, or 6-311++G** on copper and 6-31G* basis set on all other atoms; a smaller basis set on copper leads to unsatisfactory results. Electronic absorption spectra of six heteroleptic complexes have been predicted using TD-DFT calculations, and the transitions making up the dominant bands analysed in terms of the character of the HOMO–LUMO manifold. The calculational data reveal dominant phosphonate ligand character in the LUMO for the dye found to function most efficiently in practice, and also reveal that the orbital character in the HOMOs of the two most efficient dyes is dominated by the non-anchoring ligand 2, suggesting that ligand 2 enhances the performance of the sensitizer by minimizing back-migration of an electron from the semiconductor to the dye.

School students are growing up in a world with a rapidly changing climate, the effects of which will become increasingly apparent during their lifetimes. We designed and pilot tested “You and CO₂”, a STEAM program designed to encourage students to reflect on their personal impact on the environment, while also appreciating their place within society to bring about positive societal change. Over three interlinked workshops, students analyzed the carbon footprints of some everyday activities, which they then explored in more detail through interacting with a bespoke piece of digital fiction, No World 4 Tomorrow. The program culminated with students producing their own digital fictions, allowing them the freedom to explore the themes from the previous workshops with a setting and focus of their choice. We reflect here on the experience of running the You and CO₂ program and on the themes that emerged from the students’ original digital fictions.