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Semiconductor photocatalysis can utilize solar energy for clean energy conversion, but the catalytic efficiency is often unsatisfactory due to limited photo response and efficient separation of photogenerated carriers. In this work, 3D porous carbon nitride (3DPCN) composited oxygen vacancy‐induced indium oxide (3DPCN/VO‐In2O3) was successfully prepared and analyzed by some characterization methods. Meanwhile, the performance of photocatalytic nitrogen fixation was further investigated. X‐ray photoelectron spectroscopy and X‐Ray diffraction (XRD) confirmed the successful preparation of the composites and revealed the electron flow direction; scanning electron microscopy (SEM) and transmission electron microscopy showed the surface structure of the composites; diffuse reflectance spectroscopy and temperature programmed desorption (TPD) revealed the energy band position and adsorption mechanism; electron paramagnetic resonance (EPR) characterization confirms the successful construction of oxygen vacancies; and electrochemical impedance spectroscopy, photoluminescence, and other photochemical characterization results showed that 3DPCN/VO‐In2O3 band gap is narrower and more effective in capturing light than other materials, improving the photocatalytic nitrogen fixation ability. The test results show that the nitrogen fixation capacity of 3DPCN/VO‐In2O3 can reach a maximum value of 156 within 2 h. This result demonstrates that the modification of carbon nitride improves its nitrogen fixation effect, and the introduction of oxygen vacancy‐induced In2O3 improves the light absorption performance and is advantageous to the separation of photogenerated charge carriers.

Solar‐driven reduction of nitrogen to ammonia is a promising green approach and is considered as a sustainable alternative to the Haber–Bosch process. Carbon nitride (g‐C3N4) is an ideal non‐metallic semiconductor photocatalyst for photocatalytic N2 reduction reaction (p‐NRR). In this work, we designed a simple supramolecular self‐assembly method to prepare copper‐doped porous graphitic nitride (Cu@pg‐C3N4) photocatalysts. The synergistic semiconductor and metal interactions enabled the obtained Cu@pg‐C3N4 to achieve larger specific surface area, more efficient photogenerated carrier separation, and stronger photoreduction ability. The specific surface area of Cu@pg‐C3N4 increased from 5.69 to 75.76 μmol/L, exposing more active sites compared to bulk g‐C3N4. The NH4+ production rate of the obtained Cu@pg‐C3N4 was 150.47 μmol/L, which is 20 times higher than that of the bulk carbon nitride, exhibiting excellent N2 photofixation ability. These findings highlight the significant progress that can be achieved by metal supramolecular network modification strategies in harnessing the potential of carbon nitride for photocatalytic reduction applications.

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