Hydrogen is an ideal energy carrier and is environmentally friendly. The energy conversion technology of semiconductor photocatalytic decomposition of water has attracted great attention. [1][2][3][4][5][6] And this technology can alleviate the energy crisis and environmental pressure. [7][8][9][10][11][12] With the increasing demand for sustainable catalytic performance, it is challenging to obtain ideal photocatalytic performance. [13][14][15][16][17][18][19][20] To obtain ideal photocatalytic performance in the process of photocatalysis, the following contents need to be optimized: the absorption range of light, the separation of photogenerated electron-hole pairs, and the redox ability of electrons and holes. [21] In fact, a large number of semiconductor catalysts have been cleverly designed for photocatalytic hydrogen evolution. Among them, the most common is to enhance the synergistic effect by matching the energy band position of semiconductors to form heterojunction structures, resulting in high visible light absorption and rapid photoelectron transfer. [22][23][24][25][26][27] Metal-organic framework (MOF) materials have been suggested to be used as photocatalysts in the field of photocatalytic hydrogen production because of their structural diversity and large specific surface area. [21,28] More and more people begin to study the combination of some nanomaterials and MOF materials to improve the catalytic ability of MOF materials. For example, a highly efficient photocatalyst NH 2 -MIL-125 (Ti)/g-C 3 N 4 /NiPd reported in the literature mainly adds NiPd nanoparticles to the close contact heterojunction interface, thus showing excellent photocatalytic hydrogen evolution performance. [29] The hydrogen release rate of MIL-125-NH 2 @TiO 2 core-shell particles synthesized by a solvothermal method is increased by 70 times. [30] It can be seen that the combination of MOF materials and other semiconductor materials will be beneficial to enhance photocatalytic performance. In view of the above research, we combine MOF material NH 2 -MIL-53 (Al) with semiconductor material Co 3 O 4 to enhance the photocatalytic activity of aluminum MOF. Among them, Al is the most abundant metal element in the earth's crust. [31] According to the study, MOF based on aluminum carboxylate coordination is relatively stable in this system. [32] In addition, the material Co 3 O 4 is derived from zeolitic imidazolate framework-9 (ZIF-9). It is often used in photocatalytic reactions because of its large specific surface area and porous structure. [33] In this work, NH 2 -MIL-53 (Al) was hydrothermally synthesized and Co 3 O 4 was prepared by calcining ZIF-9 in air. Later 2D/3D Co 3 O 4 /NH 2 -MIL-53 (Al) composites were synthesized by in situ ultrasonic stirring method. The structure, photoelectric performance, and catalytic activity of the catalyst were studied by various characterization methods. Finally, the direction of charge transfer is further illustrated by in situ irradiation X-ray photoelectron spectroscopy (XPS) and DFT calcul...