Mesoporous silica nanospheres supported atomically precise palladium nanocluster: Highly efficient and recyclable catalysts in the reduction of 4‐nitrophenol and Heck reactions

Abstract

Atomically precise palladium nanoclusters show great potential applications in the field of catalysis owing to its ultrasmall size and precise structure. This work, we report the mesoporous silica nanoparticles (MSNs) supported [Pd3Cl(PPh3)3(PPh2)2]Cl catalysts (denoted as Pd3Cl/MSNs) for the reduction of 4‐nitrophenol and Heck coupling reactions of iodobenzene and styrenes. High uniform MSNs, with average diameter ≈110 nm, were prepared by sol–gel method, followed by Pd nanoclusters immobilization into the pore of MSNs. The MSNs supported Pd nanoclusters were well characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT‐IR), and diffuse reflectance optical spectrum. The results indicated that Pd3Cl nanoclusters after immobilized into the pores of MSNs are intact and possess good dispersibility. The catalytic performance of as‐prepared nanocomposites was evaluated by the reduction of 4‐nitrophenol and Heck reactions. The 4‐nitrophenol could be completely conversion to 4‐aminophenol within 6 min. Meanwhile, the as‐prepared Pd3Cl/MSNs exhibit excellent catalytic performance in the Heck reactions between iodobenzenes and styrenes. The high catalytic activity of Pd3Cl/MSNs could be attributed to the large surface area and unique geometric structure of as‐prepared Pd nanoclusters. More importantly, the catalysts could be easily recycled by centrifugation and shows excellent reusability.

Atomically precise nanocluster-catalyzed coupling reactions

“…Recently, Gao et al have reported that the mesoporous silica nanoparticle (MSN)-supported [Pd 3 (PPh 3 ) 3 (PPh 2 ) 2 ]Cl (Pd 3 Cl/MSN) catalyzed the Heck reaction between iodobenzene and styrene. 74 They have followed Zhu's synthesis method 57 mentioned in the S–M coupling reaction section. Pd 3 Cl was mounted on MSNs by physically mixing and annealing at 100 °C in a vacuum oven before further treatment.…”

Acetate Ions Facilitated Immobilization of Highly Dispersed Transition Metal Oxide Nanoclusters in Mesoporous Silica

“…In direct synthesis, dopant compounds directly participate in the co-condensation and self-assembly of silanol species during mesoporous silica synthesis, resulting in a uniform distribution of doped species. − However, it should be noted that some mesoporous silica materials (e.g., SBA, FDU, and KIT series) require strongly acidic synthesis conditions, making it challenging to achieve heteroatom incorporation via polycondensations due to hybrid species existing as cations rather than oxo species under such conditions. In contrast, the postmodification method offers a more universally applicable approach for functionalizing mesoporous silica materials. ,− This involves immobilizing the desired chemical species within their mesopores, which is less constrained by synthesis conditions. The immobilization of fine particles, including metals, transition metal oxides (TMO)/sulfides, metal–organic frameworks, and active biomass, on the inner surface of mesoporous silica expands their applications, especially in heterogeneous catalysis such as water splitting, epoxidation, esterification, CO 2 hydrogenation, pollutant degradation, biodiesel production, and alkane reforming. − …”