Structuring Pd Nanoparticles on 2H-WS₂ Nanosheets Induces Excellent Photocatalytic Activity for Cross-Coupling Reactions under Visible Light

Abstract

Effective photocatalysts and their surface engineering are essential for the efficient conversion of solar energy into chemical energy in photocatalyzed organic transformations. Herein, we report an effective approach for structuring Pd nanoparticles (NPs) on exfoliated 2H-WS nanosheets (WS/PdNPs), resulting in hybrids with extraordinary photocatalytic activity in Suzuki reactions under visible light. Pd NPs of different sizes and densities, which can modulate the photocatalytic activity of the as-prepared WS/PdNPs, were effectively structured on the basal plane of 2H-WS nanosheets via a sonic wave-assisted nucleation method without any reductants at room temperature. As the size of Pd NPs on WS/PdNPs increased, their photocatalytic activity in Suzuki reactions at room temperature increased substantially. In addition, it was found that protic organic solvents play a crucial role in activating WS/PdNPs catalysts in photocatalyzed Suzuki reactions, although these solvents are generally considered much less effective than polar aprotic ones in the conventional Suzuki reactions promoted by heterogeneous Pd catalysts. A mechanistic investigation suggested that photogenerated holes are transferred to protic organic solvents, whereas photogenerated electrons are transferred to Pd NPs. This transfer makes the Pd NPs electron-rich and accelerates the rate-determining step, i.e., the oxidative addition of aryl halides under visible light. WS/PdNPs showed the highest turnover frequency (1244 h) for photocatalyzed Suzuki reactions among previously reported photocatalysts.

Metal Sulfide Photocatalysis: Visible‐Light‐Induced Organic Transformations

“…Building Pd nanoparticles on 2H-WS 2 nanosheets brought a new idea for Suzuki-Miyaura coupling reaction (Scheme 25a). [80] These Pd/2H-WS 2 nanoparticles whose 2H-WS 2 nanosheets were mixed with Pd(OAc) 2 in ethylene by sonication exhibit superior photocatalytic activities under 60 W white LED irradiation. Similarly, Pd-nanodot decorated MoS 2 nanosheets could also animate the Suzuki-Miyaura reaction under Xe lamp irradiation (Scheme 25b).…”

Visible‐Light‐Enhanced Suzuki–Miyaura Reactions of Aryl Chlorides in Water with Pd NPs Supported on a Conjugated Nanoporous Polycarbazole

“…In light of the above experimental results and previous literature reports, we propose a reaction mechanism as depicted in Scheme . Upon blue LED irradiation, CNP generates electron–hole pairs, followed by transfer of the photoexcited electrons to Pd 0 , leading to the separation of the excited charges and holes.…”

“…High yields could also be obtained in alcohols and DMF (entries 2-5). The same reactiong ave lower yields with lower selectivityi nDMSO, CH 3 CN, and CHCl 3 (entries [6][7][8]. The screening of different bases (entries 9-16)r evealed that KOH was slightly more selective than NaOH and tBuOK,b ut K 3 PO 4 was still the best base for this photo-induced SMC reaction.…”

“…[4] Au-Pd nanostructure photocatalysts have also been developed by making use of the localized surface plasmon resonance of gold nanocrystals to enhance SMC. [5] Other recently developed cooperative photocatalysts include GO-Pd@Ag-AgBr (GO = graphene oxide), [6] 2H-WS 2 /Pd, [7] Pd-MoS 2 , [8] Pd/SiC, [9] and Pd-Au/TiO 2 . [10] Polydopamine nanofilms, [11] poly(benzoxadiazole), [12] thioether-containing covalent organicf rameworks, [13] and metal-organic frameworks [14] with broad light absorption have also been used as visible light-harvestingi nterfaces for Pd nanocrystal-catalyzed coupling reactions.…”

Heterogeneous Photocatalyzed C−C Cross‐coupling Reactions Under Visible‐light and Near‐infrared Light Irradiation

“…The visible light photocatalysts with high catalytic performance for photocatalyzed C−C cross‐coupling reactions could be prepared by loading Pd active metal on the surface of the 2D semiconductor materials. It was reported that exfoliated 2H‐WS 2 supported Pd nanoparticle photocatalyst (2H‐WS 2 /Pd) exhibited excellent photocatalytic activity in Suzuki C−C cross‐coupling reactions under visible light . In this work, effects of solvents, bases, coverage and size of Pd nanoparticles on the photocatalytic activity of 2H‐WS 2 /Pd nanostructures as well as the photocatalytic mechanism for Suzuki C−C cross‐coupling reactions under visible light have been studied and discussed in detail (Figure ).…”