Scheme 1. Schematic illustration of the design and controlled synthesis process of spatially separated CoO x and IL-modified BVO/CN (CoO x -BVO/CN-IL).

Graphite phased carbon nitride (g‐C3N4) has attracted extensive attention attributed to its non‐toxic nature, remarkable physical–chemical stability, and visible light response properties. Nevertheless, the pristine g‐C3N4 suffers from the rapid photogenerated carrier recombination and unfavorable specific surface area, which greatly limit its catalytic performance. Herein, 0D/3D Cu‐FeOOH/TCN composites are constructed as photo‐Fenton catalysts by assembling amorphous Cu‐FeOOH clusters on 3D double‐shelled porous tubular g‐C3N4 (TCN) fabricated through one‐step calcination. Combined density functional theory (DFT) calculations, the synergistic effect between Cu and Fe species could facilitate the adsorption and activation of H2O2, and the separation and transfer of photogenerated charges effectively. Thus, Cu‐FeOOH/TCN composites acquire a high removal efficiency of 97.8%, the mineralization rate of 85.5% and a first‐order rate constant k = 0.0507 min−1 for methyl orange (MO) (40 mg L−1) in photo‐Fenton reaction system, which is nearly 10 times and 21 times higher than those of FeOOH/TCN (k = 0.0047 min−1) and TCN (k = 0.0024 min−1), respectively, indicating its universal applicability and desirable cyclic stability. Overall, this work furnishes a novel strategy for developing heterogeneous photo‐Fenton catalysts based on g‐C3N4 nanotubes for practical wastewater treatment.

Sensitive and selective optoelectronic detection of NO 2 with g-C 3 N 4 (CN) is critical, but it remains challenging to achieve ultralow concentration (ppb-level) detection. Herein, Ni metal−organic frameworks/CN nanosheet heterojunctions were successfully fabricated by the electrostatic induced assembly strategy and then treated by a post-alkali etching process for creating coordinatively unsaturated Ni(II) sites. The optimized heterojunction exhibits a record detection limitation of 1 ppb for NO 2 , well below that observed on pristine CN, and an outstanding selectivity over other gases, along with long-time stability (120 days) at room temperature. The resulting superior detection performance benefits from the enhanced charge transfer and separation of the closely contacted heterojunction interface and the favorable adsorption of NO 2 by unsaturated Ni(II) as selective adsorption sites mainly by means of the time-resolved photoluminescence spectra and in situ X-ray photoelectron spectra. Moreover, the in situ Fourier transform infrared spectra and temperature-programmed desorption disclose that the promotion adsorption of NO 2 depends on the strengthened interaction between NO 2 and Ni(II) node sites at the aid of OH groups from unsaturated coordination. This work offers a versatile solution to develop promising CN-based optoelectronic sensors at room temperature.

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