Flat and Stretched Delafossite α-AgGaO₂: Manipulating Redox Chemistry under Visible Light

Abstract

The shape engineering of semiconductor photocatalysts has been frequently employed to improve the charge separation and thus the photocatalytic performance of hydrogen evolution and CO2 reduction, yet in the photosynthesis of value-added compounds, it is rarely reported. Here, we show that the photocatalytic reaction kinetics of several reductive and oxidative homocoupling processes can be manipulated via shape engineering of the AgGaO2 delafossite. While the flat AgGaO2 with dominant, electron-rich (001) facets shows a 20-fold enhancement over the stretched AgGaO2 with dominant, hole-rich (012) facets in the reductive homocoupling of benzyl bromide, the stretched AgGaO2 performs 4 times better than the flat AgGaO2 in the oxidative homocoupling of aniline. The shape engineered AgGaO2 can also be employed for efficient reductive coupling of nitrobenzenes and oxidative coupling of amines for the synthesis of azobenzenes and imines.

Mesoporous Mixed-Metal–Organic Framework Incorporating a [Ru(Phen)3]2+ Photosensitizer for Highly Efficient Aerobic Photocatalytic Oxidative Coupling of Amines

“…The development and full use of clean energy have been an essential research focus in recent decades. − Among many clean energy sources, sunlight is considered one of the best natural sources, and the organic transformation driven by visible light has successfully converted solar energy into chemical energy. − Under visible light irradiation with sufficiently high energy, a series of photoactivated chemical reactions could occur accompanied by the initiation of complex free radical mechanisms, so photocatalysis is widely viewed as a route to the green synthesis of some chemicals due to its environmental friendliness and high sustainability. − As the critical component of photocatalysis, a variety of materials have been explored and researched to induce electron–hole separation and promote photocatalytic organic transformation. However, the most efficient and practical visible-light-driven photocatalysts are still based mainly on the soluble complexes of noble metals with strong light absorption, such as Ru and Ir. − Several strategies for the utilization of the noble metal-based photocatalysts, including designing novel Ru/Ir complex-based molecular photosensitizers via the change of the ligand structure, loading small molecular photosensitizers onto different solid materials via electric adsorption, doping or deposition, and post-modifying metal ions on the skeleton of porous materials by coordination, have been developed. ,− Yet many unavoidable problems have to be faced on account of nonrecoverability, nonrecyclability, and scarcity for some expensive homogeneous photocatalysts, but poor interface contacts between phases, inefficient charge separation and transportation, uncontrollable load capacity, and deleterious semiconductor degradation side reactions for some heterogeneous photocatalysts. − Moreover, most reported photocatalysts can only be used for a specific reaction rather than the multireaction platform. − Therefore, it remains a huge challenge to develop efficient, recyclable, stable, and versatile photocatalysts nowadays.…”

Effective Activation of Strong C−Cl Bonds for Highly Selective Photosynthesis of Bibenzyl via Homo‐Coupling

“…For example, colloidal CsPbBr 3 perovskite was reported as a photosensitizer for the homo‐coupling of benzyl bromides (7 examples, yield 42–83 %) with TON as high as 17500, but this perovskite could only be used twice, and aprotic solvent and organic scavenger with a prolonged reaction time were required (20–48 h) [16] . Modified AgGaO 2 with shape engineering was synthesized, and the flat AgGaO 2 with electron‐rich (001) facets exhibited 20 times higher activity compared to (012) facets stretched AgGaO 2 in dehalogenative homo‐coupling of benzyl bromides (5 examples, yield 75–83 %) [17] . The hole‐rich stretched AgGaO 2 , on the other hand, showed better photocatalytic performance in the oxidative homo‐coupling of aniline, extending shape engineering in tuning selectivity for coupling reactions.…”

“…Alkyl halides are important reactants in constructing CÀ C bond for fine chemicals, pharmaceutically active compounds and agricultural chemicals. [19] Compared with alkyl chloride, alkyl bromides have been used and reported more intensively [16][17][18][20][21][22][23][24] because CÀ Br bond has a much lower energy (285 kJ mol À 1 ) than that of CÀ Cl (327 kJ mol À 1 ), [25] so the former is more easily activated and the product selectivity is also well controlled. However, alkyl chlorides have superior properties than alkyl bromides, [26] such as low-cost and abundance and reduced toxicity.…”

Substrate-Induced Anisotropic Growth of CuAlO2 Platelets in a Liquid–Solid Reaction

“…4 It has been well recognized that the photocatalytic performance of an electrode material correlates strongly with its surface microstructure. 5 Sun et al 6 suggested that flat AgGaO 2 particles capped mainly with electron-rich (0001) facets showed a 20-fold enhancement over the stretched AgGaO 2 ones in the reduction of benzyl bromide. CuAlO 2 , as the same delafossite-type laminar compound as AgGaO 2 , also possesses a high anisotropy of the electrical conductivity along the a-and c-axes.…”