Morphology‐Tuned Exceptional Catalytic Activity of Porous‐Polymer‐Supported Mn₃O₄ in Aerobic sp³ CH Bond Oxidation of Aromatic Hydrocarbons and Alcohols

Abstract

Mn3O4 nanomaterials with different morphologies (sphere, nanowire, and octahedron) embedded into functionalized nanoporous polymers were developed by a facile one‐pot solvothermal technique at different temperatures. These Mn3O4‐based hybrid materials could behave as heterogeneous nanocatalysts to perform sp3 CH bond oxidation of aromatic hydrocarbons and alcohols with molecular oxygen as an economic oxidant. Catalytic activity could be effectively tuned by changing the morphology of incorporated Mn3O4 in nanoporous polymer. These Mn3O4‐based hybrid materials exhibited remarkable catalytic performance for sp3 CH bond oxidation as compared with bare Mn3O4 nanoparticles. Mn3O4 with octahedral morphology in nanoporous polymer exhibited the highest catalytic activity on account of its more exposed crystallographic planes and edges. These Mn3O4‐based nanocatalysts could be recycled and reused for consecutive catalytic cycles without a significant loss of catalytic activity.

Advances in Nanostructured Metal-Encapsulated Porous Organic-Polymer Composites for Catalyzed Organic Chemical Synthesis

“…During the synthesis of Ru-B and Ru-C, ethylene glycol was used as the reducing agent, which acted as a stabilizer that controlled particle growth and inhibited aggregation [51]. Borah et al [55] reported Mn 3 O 4 nanoparticles that were homogeneously dispersed over the surface of the DVTA polymer on the basis of TEM images of Mn@DVTA1, while a nanowire-like morphology of Mn 3 O 4 nanomaterials, with an average length of 0.8 mm, was observed for Mn@DVTA2 and Mn@DVTA3; these nanowires were revealed to fuse, even at high temperatures, to form octahedral Mn 3 O 4 particles. Singuru et al [62] used TEM to observe monodispersed needle-like Mn 3 O 4 NPs with widths in the 30-250 and 7-12 nm ranges that were firmly surrounded by a porous organic polymer with a 3D flame-like form composed of an interconnected 3D porous network, while flake-like irregular blocks with rough surfaces of aggregated nanoparticles were observed in the SEM images of the as-synthesized POP and Mn 3 O 4 @POP [54].…”

“…Several studies have shown that XRD is an appropriate technique for exploring structures of POP-based materials [64]. The literature reveals that POP supports exhibit broad XRD patterns that show the presence of amorphous phases, while metal-encapsulated POPs exhibit sharp peaks consistent with the presence of crystallized metal nanoparticles inside their polymer frameworks, as shown in Figure 1a,b [52][53][54][55]. The amorphous nature of POPs was considered to be a drawback from the perspective of structural analysis; however, XRD is able to swiftly determining the presence of viable materials in a reaction mixture without the need to wait for crystals to form.…”

“…The BET method is the most used technique for determining surface areas and porosities of POP supports and nanocatalysts. The literature reveals that pure and metal-encapsulated POPs exhibit a sharp uptake of N 2 in the high P/P 0 pressure region ( Figure 2) [51][52][53][54][55][56][57][58][59]. These POPs contain one or more groups of pores, which are classified as micropores (<2 nm), mesopores (<50 nm), or macropores (>50 nm).…”

Design and Catalytic Application of Functional Porous Organic Polymers: Opportunities and Challenges

“…The final mixture was loaded in Teflon lined autoclave and kept at different temperatures (80, 120 and 180 ° C) for around 6 hours. These catalysts were designated as Mn@DVTA‐1, Mn@DVTA‐2 and Mn@DVTA‐3 respectively (Scheme ) . The BET surface areas of Mn@DVTA‐1, Mn@DVTA‐2, and Mn@DVTA‐3 catalysts were found to be 546, 656 and 948 m 2 g −1 respectively.…”

Pd NPs Decorated on POPs as Recyclable Catalysts for the Synthesis of 2‐Oxazolidinones from Propargylic Amines via Atmospheric Cyclizative CO2 Incorporation

“…The interaction between metallic nanoparticles and organic linkers in POPs can be easily elevated by incorporating coordination groups into metallic precursors, which supply an additional benefit for the improvement and stabilization of the activity of metallic nanoparticles compared with previous catalytic supports. Current works in the research study show that heterogeneous catalytic system for aerobic oxidation of morphology‐tuned system, hydrogenation, coupling reaction, reactions involving cycloaddition, and so forth can be established via the feasible fabrication and decoration of several metal NPs on the outer nanoporous cavities of POPs.…”