Fast and Selective Semihydrogenation of Alkynes by Palladium Nanoparticles Sandwiched in Metal–Organic Frameworks

Abstract

The semihydrogenation of alkynes into alkenes rather than alkanes is of great importance in the chemical industry. Unfortunately, state‐of‐the‐art heterogeneous catalysts hardly achieve high turnover frequencies (TOFs) simultaneously with almost full conversion, excellent selectivity, and good stability. Here, we used metal–organic frameworks (MOFs) containing Zr metal nodes (“UiO”) with tunable wettability and electron‐withdrawing ability as activity accelerators for the semihydrogenation of alkynes catalyzed by sandwiched palladium nanoparticles (Pd NPs). Impressively, the porous hydrophobic UiO support not only leads to an enrichment of phenylacetylene around the Pd NPs but also renders the Pd surfaces more electron‐deficient, which leads to a remarkable catalysis performance, including an exceptionally high TOF of 13835 h−1, 100 % phenylacetylene conversion 93.1 % selectivity towards styrene, and no activity decay after successive catalytic cycles. The strategy of using molecularly tailored supports is universal for boosting the selective semihydrogenation of various terminal and internal alkynes.

Interwrapping Distinct Metal-Organic Frameworks in Dual-MOFs for the Creation of Unique Composite Catalysts

“…These results indicate that there occurred electron transfer from encapsulated Cu NPs to the ZIF-8 supporting matrix, leading to positively charged Cu δ+ species located on the surface of Cu NPs inside the negatively charged ZIF-8 supporting matrix. The unique interfacial interaction between Cu NPs and ZIF-8 support would weaken its combination with styrene molecules to improve the styrene selectivity in catalysis, which has been confirmed by the selective sorption experiment between alkyne and alkene molecules (Table S7) [41,45,50].…”

“…The catalytic properties are very sensitive to the Cu content in the composite materials, because the size of encapsulated Cu NPs is dependent on the Cu content, while the catalytic selectivity is related to the size of Cu NPs (Table S6). High Cu content resulted in low substrate conversion, while low Cu content led to overhydrogenation Research of styrene, due to the formation of large-and small-sized Cu NPs, respectively, revealing the structure-dependent characteristic of this catalytic reaction (Figure S76, Table S4) [36,45].…”

Photocatalytic Carboxylation of Phenyl Halides with CO2 by Metal‐Organic Frameworks Materials

“…The preparaion of MOF‐5 follows the previously‐reported method with minor revision. [ 19‐20 ] The capability of as‐prepared MOF‐5 catalysts was tested by photocatalytic experiments. The optimal photocatalytic conditions icnluding catalyst type, temperature, pressure and light were investigated using 1‐phenethyl‐ bromide as the model substrate.…”

Seed‐mediated Growth of AlloyedAg‐PdShells toward Alkyne Semi‐hydrogenation Reactions under Mild Conditions†

“…[ 5‐6 ] In addition, the Pd nanoparticles usually undergo a surface reconstruction that leads to the particle sintering during calcination and reactions and subsequently decreases their overall activities. Conventional approaches for enhancing the catalytic selectivity and stability of Pd targeting alkenes via the semi‐hydrogenation include controlling the shape of palladium nanocrystals, [ 7‐8 ] preparing isolated single‐atom Pd catalysts, [ 9‐12 ] using various supports ( e.g , TiO 2 , [ 13 ] Ni(OH) 2 , [ 14 ] mpg‐C 3 N 4 , [ 15 ] CeO 2 , [ 16‐17 ] Al 2 O 3 , [ 18 ] SiO 2 , [ 19 ] Fe 3 O 4 , [ 20 ] C, [ 21‐22 ] N‐CNT, [ 23 ] HT, [ 24 ] COF [ 25 ] and MOF [ 26‐31 ] materials), doping second elements ( e.g , Pb, [ 8,32‐33 ] Zn, [ 34‐35 ] S, [ 36 ] P, [ 37 ] C, [ 38‐39 ] Ga, [ 40‐41 ] In [ 10,42 ] ), preparing nanocomposites ( e.g , CuFe 2 O 4 , [ 43 ] Cu 2 O, [ 44 ] ZnO [ 45 ] ) and using organic modifiers (modifying elements such as N, [ 46‐51 ] S, [ 51‐55 ] or P [ 55 ] ) to poison the active sites. Nearly all these methods could increase the selectivity of Pd as a semi‐hydrogenation catalyst by regulating the electronic state (ligand effect) [ 8,12,15,36 ] or/and separating the active sites of Pd (ensemble effect).…”