This work demonstrates that a single Ru atom-modified covalent triazine framework (Ru-CTF) has selectivity for the electrooxidation of benzyl alcohol in water over the oxygen evolution reaction. Additionally, Ru-CTF displayed higher stability than an immobilized Ru-organometallic complex due to the covalently cross-linked structure of CTF.

Despite recent advances in the carbonization of organic crystalline solids like metal-organic frameworks or supramolecular frameworks, it has been challenging to convert crystalline organic solids into ordered carbonaceous frameworks. Herein, we report a route to attaining such ordered frameworks via the carbonization of an organic crystal of a Ni-containing cyclic porphyrin dimer (Ni2-CPDPy). This dimer comprises two Ni–porphyrins linked by two butadiyne (diacetylene) moieties through phenyl groups. The Ni2-CPDPy crystal is thermally converted into a crystalline covalent-organic framework at 581 K and is further converted into ordered carbonaceous frameworks equipped with electrical conductivity by subsequent carbonization at 873–1073 K. In addition, the porphyrin’s Ni–N4 unit is also well retained and embedded in the final framework. The resulting ordered carbonaceous frameworks exhibit an intermediate structure, between organic-based frameworks and carbon materials, with advantageous electrocatalysis. This principle enables the chemical molecular-level structural design of three-dimensional carbonaceous frameworks.

See supplementary material for additional information regarding the synthesis method for CNT films, experimental setup, theoretical equation for thermal measurement, details for AGF calculation and absolute values of experiment/simulation data.

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Solid solutions between ZnSe and Cu(In, Ga)Se2 (ZnSe:CIGS) have promising properties as photocathodes for solar hydrogen production from water, such as a long absorption edge of about 900 nm and a large driving force for reaction, >0.9 V, originated by a deep valence band maximum of 1.0–1.1 V vs normal hydrogen electrode (NHE). However, their performance is limited with an incident photon-to-current conversion efficiency (IPCE) of 65% at 400 nm and a half-cell solar-to-hydrogen energy conversion efficiency (HC-STH) of 3.6% so far. Te addition during ZnSe:CIGS thin film deposition by vacuum co-evaporation clearly decreased the optimal deposition temperature from 450 to 380 °C and resulted in columnar shaped grains of submicrometer size in diameter and with almost no grain boundary between the film surface and the backside electrode of Mo, which is significantly larger than the case of without Te addition. Interestingly, a Ga/In compositional ratio gradient was further introduced to the depth profile, which can facilitate charge separation. Structural characterizations using XRD and cross-sectional transmission electron microscopy revealed that the composition gradient was mainly formed by the diffusion of In through grain boundaries in the Ga-rich layer, and thus, the mixing between the Ga-rich and In-rich layers was more significant at a lower deposition temperature owing to the smaller grain size. The photocathode fabricated from the ZnSe:CIGS thin film with the composition gradient showed a very high IPCE of 89% at 540 nm and 0 V vs the reversible hydrogen electrode, and HC-STH of 3.7%, which is higher than values reported thus far. In conclusion, it is clarified that the potential gradient, which can be introduced by composition gradient, is beneficial for photoelectrodes and photocatalysts to achieve higher performance.