2D amorphous transition metal oxides (a‐TMOs) heterojunctions that have the synergistic effects of interface (efficiently promoting the separation of electron−hole pairs) and amorphous nature (abundant defects and dangling bonds) have attracted substantial interest as compelling photocatalysts for solar energy conversion. Strategies to facilely construct a‐TMOs‐based 2D/2D heterojunctions is still a big challenge due to the difficulty of preparing individual amorphous counterparts. A generalized synthesis strategy based on supramolecular self‐assembly for bottom–up growth of a‐TMOs‐based 2D heterojunctions is reported, by taking 2D/2D g‐C3N4 (CN)/a‐TMOs heterojunction as a proof‐of‐concept. This strategy primarily depends on controlling the cooperation of the growth of supramolecular precursor and the coordinated covalent bonds arising from the tendency of metal ions to attain the stable configuration of electrons, which is independent on the intrinsic character of individual metal ion, indicating it is universally applicable. As a demonstration, the structure, physical properties, and photocatalytic water‐splitting performance of CN/a‐ZnO heterojunction are systematically studied. The optimized 2D/2D CN/a‐ZnO exhibits enhanced photocatalytic performance, the hydrogen (432.6 µmol h−1 g−1) and oxygen (532.4 µmol h−1 g−1) evolution rate are 15.5 and 12.2 times than bulk CN, respectively. This synthetic strategy is useful to construct 2D a‐TMOs nanomaterials for applications in energy‐related areas and beyond.

Hydrogen, as a clean fuel, has been considered as a promising alternative for traditional fossil fuels in the future. [1] The photocatalysis hydrogen evolution is identified as one of pollution-free methods to produce hydrogen on a large scale. [2][3][4] Since photo-induced water splitting on TiO 2 electrodes was discovered, great efforts have been made to develop catalysts for photocatalytic water splitting. [5,6] Up to date, various nanomaterials have been used as photocatalysts for the sunlightdriven H 2 evolution, including metal oxides/sulfide, carbonaceous materials. [7][8][9][10] Among them, CoO nanocrystal is a wellknown visible-light response (E g % 2.6 eV) photocatalyst that can be used for photocatalytic water splitting. [11] Unfortunately, the photocatalytic performance of CoO nanocrystals are far away from the satisfaction for practical large-scale applications. [12] In addition, the CoO photocatalystis can be easily deactivated after a short reaction. There are two main reasons have been reported, one of which corresponds to CoO nanoparticles aggregation after reaction, the other reason originates from the unintended thermo-induced oxidation of CoO during photocatalytic process, resulting in the poor stability. [13,14] Therefore, it is still challenging task to improve the activity and durability of CoO photocatalysts.Recently, several works have been reported that amorphous cobalt-based oxides play a critical role in improving the photocatalytic performance due to the high density of dangling bonds and active sites. [15][16][17] For example, the amorphous CoO (a-CoO) can be served as an efficient and long-term stability photocatalyst for water splitting. [18] Alternatively, the combination of a-CoO with other semiconductors to construct a 2D/2D heterojunction might be an available route to utilize the complementary advantages of each component and effectively separate the photogenerated electron-hole pairs, thus improving the photocatalytic activity. [19,20] Whereas, the preparation of CoO often requires the calcination of Co-containing reagents in an inert environment, and the obtained CoO is mostly a bulk material. [11,21] Undoubtedly, solving the CoO aggregation and synthesis 2D CoO nanosheets have been of significant importance for its practical application in photocatalysis. Therefore, it is still a big challenge about explore suitable strategies to achieve the preparation of 2D/2D CoO-based heterojunctions.Graphitic carbon nitride (g-C 3 N 4 ) is generally known as a typical metal-free layered polymer, which has attracted dramatic interest in the field of visible-light-induced

In article number http://doi.wiley.com/10.1002/pssr.202100254, Bing‐Xin Zhou, Gui‐Fang Huang, Wei‐Qing Huang, and co‐workers report Co–N covalently bridged 2D/2D CN/a‐CoO heterojunctions for enhanced photocatalytic water splitting. The 2D/2D CN/a‐CoO heterojunction demonstrates wide visible‐light absorption owing to the introduction of disordered a‐CoO, and high light‐harvesting ability due to the multiple scattering in the tubular heterojunction.

Intricate hollow transition‐metal oxides (TMOs)‐based hetero‐nanostructures demonstrate intriguing applications in electronics, energy storage, and catalysis owing to their exotic electronic features and geometric complexity; however, manipulating their topological features and interfacial interactions of different subunits, is a grand challenge because most TMOs are intrinsic non‐layered crystals. Herein, a generalized multidentate ligand chelating‐grafting strategy for creating various amorphous TMOs‐based triple‐layered hetero‐nanotubes with face‐to‐face contact is demonstrated, by taking ethylenediamine tetraacetic acid (EDTA) chelating agent and melamine‐cyanuric acid (M‐CA) supramolecular complex‐polymer as a proof‐of‐concept. This strategy primarily depends on controlling the chelation of coordinated covalent bonds and grafting of hydrogen bonds, in which EDTA is utilized to chelate metal ions, and subsequently grafted to M‐CA supramolecular surface, followed by annealing treatment. Merited by the optimized structure in three natures of nanotubes‐interface‐heterolayers, the obtained hollow nanostructure possesses superior photocatalytic performance: the optimized a‐ZnO/C/CN hetero‐nanotube exhibits high hydrogen evolution rate of 400.01 μmol h−1 g−1, outperforming the bulk CN by about 14.29‐fold. The synthesis of various a‐TMOs‐based complex hollow nanostructures and the demonstration of high catalytic activity are expected to enable fundamental studies of cavity, hereto‐interface, and dimensionality effects on their properties and facilitate their use in catalysis and other applications.