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A low-molecular-weight gel is one that is organized by small molecules via noncovalent bonds, and some low-molecular-weight gels already being used in our daily lives. In general, the mechanism of formation of low-molecular-weight gels involves the gelation of solvents such as ethanol and water in the presence of low-molecular-weight gelators, which have larger molecular weights than the solvents. The gelator creates a supramolecular network via noncovalent bonds, and this network holds the solvent molecules, causing them to lose fluidity and thereby promoting gelation. That is, low-molecular-weight gels do not self-assemble and gelate solvent molecules themselves; the literature contains no reports of the self-assembly and gelation of extremely small solvent molecules such as ethanol and water. However, in this work, we found that ethanol molecules themselves form a large gel structure by self-assembling with few-nanometer-diameter oxide nanoparticles and water molecules. Our finding reveals an intriguing phenomenon where ethanol molecules support the main structure of a large gel structure through supramolecular assembly via hydrogen bonding. The key factor for the gelation of ethanol observed in this study is the presence of BaZrO3 nanoparticles, which are positively charged and homogeneously dispersed. When these nanoparticles and water were present, we observed the gelation of a substantial amount of ethanol, which would not normally occur. Our results overturn the common belief that extremely small molecules such as ethanol cannot function as a main bearer of gelatinization, and our discovery opens a path to the development of a novel self-assembly system that has not been previously reported. In addition, because the method proposed in the present work can potentially be used to prepare gels that incorporate other extremely small molecules having hydrogen bonds, we expect our findings to lead to the development of various novel materials with unique functions.

To suppress CO2 emissions, technologies that incorporate CO2 capture, utilization, and storage are being actively developed. Particularly, batteries using CO2 redox reactions are one of the most promising systems that combine energy conversion and storage. However, the stoichiometric reactions of CO2 and metal restrict the CO2 storage capacity of previously proposed systems. Applying catalyst-mediated CO2 redox is expected to provide flexible control of the CO2 storage capacity without dependence on the metal content. Herein, we report novel aqueous flow battery using CO2–formate redox with a bifunctional homogeneous Ir catalyst. Using of an Ir catalyst bearing a 4-hydroxy-N-methylpicolinamidate ligand was demonstrated for 50 cycles, with a maximum discharge capacity of 1.5 Ah L-1, capacity decay of 0.20% cycle-1, and total turnover number of 3,500. Furthermore, as the design concept, the CO2 storage capacity of the catalyst-based flow battery was improved more than 1000 times compared to the previously proposed system.

We performed X-ray absorption studies for the electrolytes of a Ti-Mn redox flow battery (RFB) to understand the redox reaction of the Ti/Mn ions and formation of precipitates in charged catholyte, because suppression of the disproportionation reaction is a key to improve the cyclability of Ti-Mn RFB and enhance the energy density. Hard X-ray absorption spectroscopy with a high transmittance and soft X-ray absorption spectroscopy to directly observe the 3d orbitals were complementarily employed. Moreover, the Ti/Mn 3d electronic structure for each precipitate and solution in the charged catholyte was investigated by using scanning transmission X-ray microscopy: the valence of Mn in the precipitate is mostly attributed to 4+, and the solution includes only Mn