Huijie He

Abstract Photocatalytic hydrogen production has been considered a promising approach to obtain green hydrogen energy. Crystalline porous materials have arisen as key photocatalysts for efficient hydrogen production. Here, we report a strategy to in situ photodeposit platinum clusters as cocatalyst on a covalent organic framework, which makes it an efficient photocatalyst for light-driven hydrogen evolution. Periodically dispersed adsorption sites of platinum species are constructed by introducing adjacent hydroxyl group and imine-N in the region of the covalent organic framework structural unit where photogenerated electrons converge, leading to the in situ reduction of the adsorbed platinum species into metal clusters by photogenerated electrons. The widespread platinum clusters on the covalent organic framework expose large active surface and greatly facilitate the electron transfer, finally contributing to a high photocatalytic hydrogen evolution rate of 42432 μmol g −1 h −1 at 1 wt% platinum loading. This work provides a direction for structural design on covalent organic frameworks to precisely manipulate cocatalyst morphologies and positions at the atomic level for developing efficient photocatalysts.

Abstract It is a great challenge to design active and durable oxygen evolution reaction (OER) electrocatalysts for proton exchange membrane (PEM) electrolyzer due to the high dissolution of electrocatalysts in acidic solution. Herein, the Nd‐doped RuO 2 (Nd 0.1 RuO x ) is developed for enhanced oxygen evolution in 0.5 m H 2 SO 4 solution with an overpotential of 211 mV to achieve 10 mA cm −2 . The theoretical calculation reveals that the improved activity of Nd 0.1 RuO x is due to the moderate decrease of d‐band center energy, which balances the adsorption and desorption of oxygen intermediates. Moreover, the formation of more high valence state Ru 4+ in Nd 0.1 RuO x is beneficial to the chemical stability of Ru species during the OER process, indicating that the introduction of Nd can effectively suppress the dissolution of Ru in acidic electrolytes. In addition, the PEM electrolyzer using Nd 0.1 RuO x /CC as the anode can be operated at 10 mA cm −2 stably for 50 h. This study sheds new light on the design of the OER catalysts in acid by engineering the electronic structure of RuO 2 .

Abstract Integrating a molecular catalyst with a light harvester into a photocatalyst is an effective strategy for solar light conversion. However, it is challenging to establish a crystallized framework with well‐organized connections that favour charge separation and transfer. Herein, we report the heterogenization of a Salen metal complex molecular catalyst into a rigid covalent organic framework (COF) through covalent linkage with the light‐harvesting unit of pyrene for photocatalytic hydrogen evolution. The chemically conjugated bonds between the two units contribute to fast photogenerated electron transfer and thereby promote the proton reduction reaction. The Salen cobalt‐based COF showed the best hydrogen evolution activity (1378 μmol g −1 h −1 ), which is superior to the previously reported nonnoble metal based COF photocatalysts. This work provides a strategy to construct atom‐efficient photocatalysts by the heterogenization of molecular catalysts into covalent organic frameworks.

Two-dimensional (2D) photocatalytic material is a vital project for modern solar energy conversion and storage. Despite a vast family of potential 2D photocatalysts that is demonstrated, their commercial applications are severely limited because of fast photogenerated electron–hole recombination. Here, based on first-principles, we propose a general paradigm to boost the separation of photoexcited charge carriers in 2D photocatalysts by stacking engineering. Taking the emerging water splitting photocatalyst MoSi2N4 as an example, we show that specific interlayer stacking-induced electric polarization plays a significant role in altering the electronic properties and thus the suppressed recombination rate of photoexcited carriers. Moreover, we find that the catalytic performance can be further controlled by vertical strain. These generalized findings not only highlight the importance of stacking-induced electric polarization but also offer new prospects for the design and application of 2D photocatalysts.

Abstract Imines are important intermediates in drug synthesis. Photocatalytic aerobic oxidative coupling of amines has been considered as a clean and promising way to produce imines and has attracted great attention. Herein, we designed and synthesized a novel two‐dimensional porphyrin‐based covalent organic framework (Por‐BC‐COF) which adopts an AA stacking mode with excellent crystallinity, high Brunauer–Emmett–Teller surface areas (1200 m 2 g −1 ), wide light absorption range (200–1300 nm) and good stability in a variety of organic solvents. Por‐BC‐COF can be used as a metal‐free heterogeneous photocatalyst for the photocatalytic oxidation of amines to imines under visible light and red light with a high yield (97 %). This work presents a novel and efficient COF photocatalyst in the application of light‐driven organic synthesis.