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Inspired by the unique band structure of CsPbBr3, we have developed an asymmetric Cl‐exchange strategy based on the CsPbBrxCl3‐x/TiO2 heterojunction‐type catalyst and achieved photocatalytic activation of C(sp3)−H bond using the toluene oxidation reaction as a proof‐of‐concept application. The anion exchange at the supported CsPbBr3 surface results in the CsPbBrxCl3‐x/TiO2 structure with an asymmetric distribution of halide. The resultant heterojunction‐type catalysts exhibit significantly improved photocatalytic activity for toluene oxidation reaction with the highest benzaldehyde production rate at 1874 μmol g−1 h−1 (∼4 times that of the naked CsPbBr3 nanocrystals). The remarkable photocatalytic performance can be ascribed to the improved carrier transport at CsPbBrxCl3‐x/TiO2 interface enabled by the unique band structure due to the asymmetric halide distribution, verified by the micro‐strain discovered through the X‐ray diffraction. This work demonstrates a new pathway to fabricate highly‐efficient halide perovskite heterojunction‐type catalysts for photocatalytic activation of C(sp3)−H bond. [ABSTRACT FROM AUTHOR]

A CsPbBr3@Ag-C3N4 ternary heterojunction photocatalyst with g-C3N4 as ballistic electron transport "tunnel" is designed and synthesized. The photogenerated electrons of CsPbBr3 dots can be efficiently transferred to Ag nanoparticles via g-C3N4 sheets, resulting in efficient CO2 reduction. The structured design of catalyst provides a novel insight for the development of perovskite-based photocatalysts. [Display omitted] • CsPbBr 3 @Ag-C 3 N 4 ternary heterojunction photocatalyst is designed and synthesized. • The photogenerated electrons of CsPbBr 3 QDs can be efficiently transferred to Ag nanoparticles via g-C 3 N 4 as the electron transport tunnel. • The CsPbBr 3 @Ag-C 3 N 4 ternary photocatalyst achieves a conversion rate of 19.49 μmol·g−1·h−1 with almost 100 % CO selectivity. • In situ DRIFT and DFT calculations reveal the photocatalytic mechanism for CO 2 reduction. Perovskite CsPbBr 3 quantum dot shows great potential in artificial photosynthesis, attributed to its outstanding optoelectronic properties. Nevertheless, its photocatalytic activity is hindered by insufficient catalytic active sites and severe charge recombination. In this work, a CsPbBr 3 @Ag-C 3 N 4 ternary heterojunction photocatalyst is designed and synthesized for high-efficiency CO 2 reduction. The CsPbBr 3 quantum dots and Ag nanoparticles are chemically anchored on the surface of g-C 3 N 4 sheets, forming an electron transfer tunnel from CsPbBr 3 quantum dots to Ag nanoparticles via g-C 3 N 4 sheets. The resulting CsPbBr 3 @Ag-C 3 N 4 ternary photocatalyst, with spatial separation of photogenerated carriers, achieves a remarkable conversion rate of 19.49 μmol·g−1·h−1 with almost 100 % CO selectivity, a 3.13-fold enhancement in photocatalytic activity as compared to CsPbBr 3 quantum dots. Density functional theory calculations reveal the rapid CO 2 adsorption/activation and the decreased free energy (0.66 eV) of *COOH formation at the interface of Ag nanoparticles and g-C 3 N 4 in contrast to the g-C 3 N 4 , leading to the excellent photocatalytic activity, while the thermodynamically favored CO desorption contributes to the high CO selectivity. This work presents an innovative strategy of constructing perovskite-based photocatalyst by modulating catalyst structure and offers profound insights for efficient CO 2 conversion. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: The heterojunction‐type structure has shown significant merits in tuning the optical properties and carrier physics. Inspired by the excellent absorption capability of halide perovskite materials for visible light, a series of CsPbBr3/TiO2 heterojunction‐type photocatalysts with various all‐inorganic‐perovskite/TiO2 ratios are successfully fabricated by the ligand‐assisted reprecipitation (LARP) method. The heterojunction structure extends the light absorption of TiO2 with good chemical and structural stability. A Pb‐O interaction at the CsPbBr3/TiO2 interface is observed by the XPS and confirmed by the TRPL showing improved interface carrier transport and stability. The heterojunction‐type catalyst shows drastically enhanced photocatalytic activity towards the direct oxidation of toluene with O2 molecule, as an important reaction for organic chemical synthesis. The optimized sample shows an activity of 2356 μmol·g–1·h–1 at 75 °C, 4 times of that of the naked CsPbBr3 nanocrystals, and 3 times of that of the bare TiO2. Based on the investigation with trapping agents, a reaction mechanism is hence proposed suggesting that the photo‐generated hole may be involved in the rate‐limiting step. This work demonstrates the potential of inorganic halide perovskite‐based heterojunction structure for photocatalytic applications. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: The heterojunction‐type structure has shown significant merits in tuning the optical properties and carrier physics. Inspired by the excellent absorption capability of halide perovskite materials for visible light, a series of CsPbBr3/TiO2 heterojunction‐type photocatalysts with various all‐inorganic‐perovskite/TiO2 ratios are successfully fabricated by the ligand‐assisted reprecipitation (LARP) method. The heterojunction structure extends the light absorption of TiO2 with good chemical and structural stability. A Pb‐O interaction at the CsPbBr3/TiO2 interface is observed by the XPS and confirmed by the TRPL showing improved interface carrier transport and stability. The heterojunction‐type catalyst shows drastically enhanced photocatalytic activity towards the direct oxidation of toluene with O2 molecule, as an important reaction for organic chemical synthesis. The optimized sample shows an activity of 2356 μmol·g–1·h–1 at 75 °C, 4 times of that of the naked CsPbBr3 nanocrystals, and 3 times of that of the bare TiO2. Based on the investigation with trapping agents, a reaction mechanism is hence proposed suggesting that the photo‐generated hole may be involved in the rate‐limiting step. This work demonstrates the potential of inorganic halide perovskite‐based heterojunction structure for photocatalytic applications. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) organic-inorganic hybrid halide perovskites have gained extensive attention in photovoltaics, photodetectors and light-emitting diodes owing to their unique optoelectronic properties and superior stability compared with their three-dimensional (3D) counterparts. However, 2D perovskites have rarely been applied for photochemical conversion applications. Herein, a series of 2D BA 2 MA n-1 Pb n Br 3n+1 perovskite nanosheets have been synthesized through a facile, ligand-free precipitation (LFP) method at room temperature. Using the specific chemical trapping techniques, we show for the first time that the 2D perovskite nanosheets can effectively generate photosensitized singlet oxygen (1O 2) via energy transfer from triplet excitons to molecular oxygen in non-polar solvent. Based on this discovery, the as-prepared BA 2 PbBr 4 and BA 2 MAPb 2 Br 7 nanosheets successfully catalyze the ENE reaction and 1,2-addition reaction between olefin and singlet oxygen under visible light. Our study is anticipated to develop and demonstrate new mechanisms for 2D halide perovskite materials in photodynamic therapy and photocatalytic applications. 2D BA 2 MA n-1 PbnBr 3n+1 perovskite nanosheets are shown for first time to effectively generate photosensitized 1O 2 via energy transfer and can catalyze the ENE reaction and the 1,2-additional reaction between olefins and O 2. This study illustrates novel mechanisms of 2D perovskite materials in photodynamic therapy and photocatalytic applications. [Display omitted] • 2D BA 2 MA n-1 Pb n Br 3n+1 nanosheets are synthesized by ligand-free precipitation method. • Photosensitized 1O 2 generation in 2D perovskites via energy transfer is first studied. • BA 2 PbBr 4 and BA 2 MAPb 2 Br 7 nanosheets can drive olefins to react with O 2 for ENE reaction and 1,2-addition reaction. [ABSTRACT FROM AUTHOR]