Spirobifluorene‐based Porous Organic Polymers as Efficient Porous Supports for Pd and Pt for Selective Hydrogenation

Abstract

Spirobifluorene‐based porous organic polymers (POP) were synthesized following two different protocols; the acetylenic coupling reaction conditions and the Sonogashira cross‐coupling reaction. These were utilized as support for the hydrogenation of a series of species containing unsaturated C=C and C=O bonds (4‐nitrostyrene, 4‐bromobenzophenone, acetophenone, 7‐nitro‐1‐tetralone and 1,2‐naphtoquinone confirmed their efficiency). POP1 prepared via a copper‐catalysis protocol was completely inactive, while POP2‐4 containing residual Pd exhibited different activities in accordance to the accessibility of the substrates to the metal. Further deposition of 0.5 wt% Pd led to active and stable catalysts. They were easily separated by filtration, and after re‐dispersion, afforded the same performances for ten successive cycles. This study also evidenced the specific role of the support in these reactions by comparing the behavior of Pd/POP with that of a Pd/C catalyst with the same loading of palladium. The deposition of Pt on these supports led to sub‐nanometric particles and, in accordance, to a different catalytic behavior reflected merely by differences in the selectivity.

Role of Polymer Structures in Catalysis by Transition Metal and Metal Oxide Nanoparticle Composites

“…A successful development of POP based on azobenzene as the catalyst activated by visible light has been carried out by Chakraborty et al 156,157 Here, the first example of a Schottky 158 Subnanometer Pd and Pt NPs have been formed via slow precipitation of Pd and Pt compounds with ammonia followed by hydrogen reduction in solid state. The authors presented extensive catalytic studies in the hydrogenation of 4nitrostyrene, 4-bromobenzophenone, acetophenone, 7-nitro-1tetralone, and 1,2-naphthoquinone, demonstrating the catalyst efficiency and stability.…”

Pt Nanoparticles Supported over Porous Porphyrin Nanospheres for Chemoselective Hydrogenation Reactions

“…Again, Garcia and others showed the utilization of Pd and Au NPs on adamantane‐based covalent organic frameworks for selective conversion of 4‐nitrostyrene to 4‐ethylnitrobenzene . Further, reports on Pd NPs supported over porous spirobifluorene framework also suggested the advantage of porous polymers as active catalyst for selective reduction of 4‐nitrostyrene to 4‐ethylnitrobenzene . All these results suggested the superiority of porous organic framework as selective and stable support for the hydrogenation reaction ,…”

“…[27] Further, reports on Pd NPs supported over porous spirobifluorene framework also suggested the advantage of porous polymers as active catalyst for selective reduction of 4-nitrostyrene to 4-ethylnitrobenzene. [28] All these results suggested the superiority of porous organic framework as selective and stable support for the hydrogenation reaction. [4b,29] We have compared the catalytic performance of Pt-POP with conventional Pt/C support, which showed very low selectivity to 4-ethylnitrobenzene (40 %) under almost similar hydrogenation reaction conditions (Table 1, entry 7).…”

A Highly Conductive All‐Carbon Linked 3D Covalent Organic Framework Film

“…This reaction has previously been used to make crystalline 2D COFs [ 14 ] and amorphous 3D porous aromatic frameworks (PAFs). [ 15 ] In TSRCF‐based synthesis, the solutions containing SBFyne, CuI, and pure solvent were mixed directly before entering the reaction chamber to minimize detrimental bulk reaction before the chamber. When SBFyne flows over the SAM modified substrate (Figure S1, Supporting Information), the terminal alkyne of SBFyne reacts with the alkyne on the SAM.…”