Porous‐Organic‐Polymer‐Triggered Advancement of Sustainable Magnetic Efficient Catalyst for Chemoselective Hydrogenation of Cinnamaldehyde

Abstract

Intriguing characteristics including high specific surface area, adjustable chemical functionality, flexibility of molecular design, high hydrothermal and mechanical stability of Porous-Organic-Polymers (POPs) present new opportunities for them to become a versatile platform in heterogeneous catalysis. Cinnamaldehyde (CAL), a representative α,β-unsaturated aldehyde, is an essential molecule, because its partially hydrogenated products, namely cinnamyl alcohol (COL) and hydrocinnamaldehyde (HCAL) are key intermediates for the production of fine chemicals including perfumes, flavorings and pharmaceuticals. In this study, we adopted a cost-effective, facile and metal & template-free strategy for the successful synthesis of hydroxyl enriched POP (denoted as TPT). The TPT was prepared by the simple one-pot condensation of triphenyl amine and terephthaldehyde in the presence of p-toluene sulphonic acid, which served as an organic catalyst. Accordingly, an integrated catalyst, Pd-Fe3O4@TPT, has been developed for the liquid phase selective hydrogenation cinnamaldehyde (CAL). Pd-Fe3O4@TPT exhibited excellent catalytic performance, providing 100% selectivity towards hydrocinnamaldehyde (HCAL) under mild reaction conditions (with relatively low hydrogen pressure and very short reaction time), whereas Fe2O3@TPT appeared inert. Compared with the conventional catalytic systems, our newly designed catalyst was superior in many aspects, owing to the rigid nature of TPT-POP, which prevents aggregation and leaching of the metal nanoparticles. We identify Pd nanoparticles (-NPs) to have two decisive roles, namely (I) transformation of Fe2O3 to Fe3O4 through metal-support interaction and (II) triggering the catalytic activity. A decrease in the Pd-Pd bond distance (~2.7 Å to ~2.49 Å) along with the shift of Fe K-edge to a lower energy was observed by the synchrotron EXAFS analysis of Pd-Fe3O4@TPT, revealing that Pd facilitated the reduction of Fe2O3 to Fe3O4. The significant enhancement in catalytic performance for the selective hydrogenation of C=C over C=O bond could be ascribed to the flat adsorption of C=C over the Pd surface and C=O bond shortening, as suggested by in-situ ATR-IR and DRIFTS spectroscopy studies. Density Functional Theory (DFT) calculations reveal two possible ways by which TPT-POP could contribute to the highly selective hydrogenation of C=C bond on the Pd-Fe3O4@TPT catalyst. Firstly, TPT acts as a structural template for generating highly concentrated Pd step sites and other low coordinated sites, which possess high activity towards C=C bond hydrogenation. Secondly, the charge transfer from TPT to the Pd clusters increases the negative charge density of the Pd sites, consequently enhancing their C=C hydrogenation activity. The present findings provide new inspirations for designing easily realizable, low-cost, and high performance catalysts for sustainable chemistry via effective surface/interface engineering.

Co3O4/Nitrogen-Doped Graphitic Carbon/Fe3O4 Nanocomposites as Reusable Catalysts for Hydrogenation of Quinoline, Cinnamaldehyde, and Nitroarenes

“…However, for the hydrogenation reaction, the presence of synergetic multifunctional catalytic sites on the two surfaces are desirable: Co 3 O 4 coated with a N-doped graphitic layer and Fe 3 O 4 enables a higher catalytic performance. Co 3 O 4 sites can activate molecular hydrogen and create a “bridge” for transferring H species by the hydrogen spillover process to the hydrogenating substrate, that is, quinoline, facilitated by Fe 3 O 4 in addition to its role played as a magnetic support. , Furthermore, a totally exposed metal surface often retards the rate of the catalytic reaction. Therefore, a graphitic shell containing a basic nitrogen atom around the surface of the metal atom leads to a higher catalytic activity.…”

“…Co 3 O 4 sites can activate molecular hydrogen and create a "bridge" for transferring H species by the hydrogen spillover process to the hydrogenating substrate, that is, quinoline, facilitated by Fe 3 O 4 in addition to its role played as a magnetic support. 5,47 Furthermore, a totally exposed metal surface often retards the rate of the catalytic reaction. Therefore, a graphitic shell containing a basic nitrogen atom around the surface of the metal atom leads to a higher catalytic activity.…”

Navigating Copper-Atom-Pair Structural Effect inside a Porous Organic Polymer Cavity for Selective Hydrogenation of Biomass-Derived 5-Hydroxymethylfurfural

“…1,2,3 Bio-refinery is a widely advanced concept to transform the biomass derived oxygenates to generate biofuel. 4,5,6 5-hydroxymethylfurfural (5-HMF) is a platform chemical of lignocelluloses valorization. Among the hydrogenated products including 2,5dihydroxymethylfuran (DHMF), 2,5-dihydroxymethyltetrahydrofuran (DHMTHF), 2,5dimethylfuran (DMF), 2,5-dimethyltetrahydrofuran (DMTHF) etc.…”

“…The limited stock of fossil fuels and growing concern about global climate change played a crucial role behind the wisdom to discover alternative energy sources, such as biomass-derived carbohydrates. − Bio-refinery is a widely advanced concept to transform biomass-derived oxygenates to generate biofuel. − 5-Hydroxymethylfurfural (5-HMF) is a platform chemical of lignocellulose valorization. Among the hydrogenated products including 2,5-dihydroxymethylfuran (DHMF), 2,5-dihydroxymethyltetrahydrofuran (DHMTHF), 2,5-dimethylfuran (DMF), 2,5-dimethyltetrahydrofuran (DMTHF), and so forth, DHMF has attracted significant attention due to tremendous application in the production of resin, ethers, and artificial fibers and as an important intermediate in drug synthesis .…”

Direct Heterogenization of the Ru-Macho Catalyst for the Chemoselective Hydrogenation of α,β-Unsaturated Carbonyl Compounds

“…In this context, numerous heterogeneous and homogeneous catalysts have been studied for chemoselective reduction of the carbonyl group of the α,β-unsaturated carbonyl compounds. − ,− ,− Here, the homogeneous catalysts show admirable reactivity for the chemoselective hydrogenation of carbonyl compounds. Alternatively, the heterogeneous catalysts exhibit noticeable benefits, including multiple-recycling ability, facile separation of products and catalysts, and easy handling, that underline the demand for developing highly efficient heterogeneous catalysts for the chemoselective reduction of α,β-unsaturated carbonyl compounds.…”