Micrometre‐sized porous polymer beads as heterogeneous molecular catalysts

Porous polymers have great potential as versatile, chemically stable catalyst supports. Yet, shaping of the resulting powders remains a challenge. Here, we demonstrate the use of suspension polymerisation to design micrometre-sized porous polymers beads containing metal binding sites. The good accessibility of the binding sites ensures high catalytic activity, which is demonstrated for two model reactions: photochemical CO2 reduction and transfer hydrogenation of aromatic ketones. Importantly, the shaping of the host material does not affect the catalytic activity of the active site

Reusable Copper Catechol‐based Porous Polymers for the Highly Efficient Heterogeneous Catalytic Oxidation of Secondary Alcohols

New catechol-based porous polymers were synthesized and used as platforms for the heterogenization of molecular Cu complexes. The resulting Cu@CatMP-1 materials proved to be highly stable and performing catalysts for the oxidation of secondary alcohols with turnover numbers up to 6000, about 1 to 2 orders of magnitude higher than the current relevant state of the art, using catalyst loadings as low as 25 ppm of Cu. The solid catalyst proved to be recyclable for over 10 runs without detectable metal leaching and has been scaled to the gram scale. The coordination of Cu to catechol within the polymer has been evidenced by X-ray absorption spectroscopy

Biological Chitin-MOF composites with hierarchical pore systems for air-filtration applications

Metal-organic frameworks (MOFs) are promising materials for gas-separation and air-filtration applications. However, for these applications, MOF crystallites need to be incorporated in robust and manageable support materials. We used chitin-based networks from a marine sponge as a non-toxic, biodegradable, and low-weight support material for MOF deposition. The structural properties of the material favor predominant nucleation of the MOF crystallites at the inside of the hollow fibers. This composite has a hierarchical pore system with surface areas up to 800 m2g-1 and pore volumes of 3.6 cm3g-1, allowing good transport kinetics and a very high loading of the active material. Ammonia break-through experiments highlight the accessibility of the MOF crystallites and the adsorption potential of the composite indicating their high potential for filtration applications for toxic industrial gases

Precursor strategies for metallic nano- and micropatterns using soft lithography

Soft lithographic methods describe a set of printing methods which are widely used for the preparation of structured surfaces. Structured surfaces are essential components in the field of (opto-)electronic devices such as organic light emitting diodes, photovoltaics or organic field effect transistors. In recent years, crucial progress has been achieved in the development of patterned metal coatings for these applications. This review focusses on new strategies for soft lithographical printing of metal structures emphasizing the subtle interplay of printing techniques, metal precursor chemistry, and surface functionalization strategies

Crystallographic insights into (CH3NH3)3(Bi2I9): A new lead-free hybrid organic-inorganic material as a potential absorber for photovoltaics

The crystal structure of a new bismuth-based light-absorbing material for the application in solar cells was determined by single crystal X-ray diffraction for the first time. (CH3NH3)3(Bi2I9) (MBI) is a promising alternative to recently rapidly progressing hybrid organic–inorganic perovskites due to the higher tolerance against water and low toxicity. Single crystal X-ray diffraction provides detailed structural information as an essential prerequisite to gain a fundamental understanding of structure property relationships, while powder diffraction studies demonstrate a high degree of crystallinity in thin films

Molecular rhodium complex within N-rich porous polymer macroligand as heterogeneous catalyst for the visible-light driven CO2 photoreduction

The heterogenization of molecular catalysts within a porous solid acting as macroligand can advantageously open access to enhanced stability and productivity, and thus to more sustainable catalytic process. We report here porous organic polymer (POP) made through metal-free polymerization using bipyridine repeating units. This N-rich POP is an efficient macroligand for the heterogenization of molecular rhodium complexes. The intrinsic catalytic activity of the heterogenized catalyst is slightly higher than that of its homogeneous molecular counterpart for formic acid production as unique carbon containing product. The heterogenization of the rhodium catalysts enables recycling for a total productivity up to 8.3 grams of formic acid per gram of catalyst after 7 cycles of reaction using visible light as sole energy source

Tailoring Pore Structure and Properties of Functionalized Porous Polymers by Cyclotrimerization

Porous polymers were prepared by cyclotrimerization reaction in molten <i>p</i>-toluenesulfonic acid. Their properties could be tailored by functionalization of the aromatic diacetyl monomers. Thus, a range of homo- and copolymers based on hydrogen-, amine-, or nitro-functionalized 4,4′-diacetylbiphenyl derivatives and 1,4-diacetylbenzene was synthesized. The pores size could be tuned from mainly microporous to hierarchical micro- and mesoporous or even hierarchical micro- and macroporous. BET surface areas up to 720 m²/g and total pore volumes up to 1.76 cm³/g were achieved. The formation of different pore types was related to the solvent–monomer/polymer interactions, which is shown by ¹⁵N solid state MAS NMR spectroscopy and SEM. Other physical properties such as surface polarity and thermal stability were influenced by the different monomers as well

Molecular Rhodium Complex within N‐Rich Porous Polymer Macroligand as Heterogeneous Catalyst for the Visible‐Light Driven CO2 Photoreduction

The heterogenization of molecular catalysts within a porous solid acting as macroligand can advantageously open access to enhanced stability and productivity, and thus to more sustainable catalytic process. Herein, a porous organic polymer (POP) made through metal‐free polymerization using bipyridine repeating units is reported. This N‐rich POP is an efficient macroligand for the heterogenization of molecular rhodium complexes. The intrinsic catalytic activity of the heterogenized catalyst is slightly higher than that of its homogeneous molecular counterpart for formic acid production as a unique carbon‐containing product. The heterogenization of the rhodium catalysts enables recycling for a total productivity of up to 8.3 g of formic acid per gram of catalyst after 7 reuses using visible light as the sole energy source

Heterogenized Molecular Rhodium Phosphine Catalyst within Metal-Organic Framework for Ethylene Hydroformylation

Molecularly-defined organometallic rhodium phosphine complexes were efficiently heterogenized within a MOF structure without affecting neither their molecular nature nor their catalytic behavior. Phosphine-functionalized MOF-808 served as solid ligand in a series of eight rhodium phosphine catalysts. These MOF-heterogenized molecular catalysts showed activity up to 2100 h-1 for ethylene hydroformylation towards pro-pionaldehyde as sole carbon-containing product. Combined experimental and computational methods applied to this unique MOF-based molecular system allowed unravelling structure and evolution of the Rh active species within the MOF under catalytic conditions, in line with molecular mechanisms at play during the hydroformylation reaction. The MOF-808 designed as a porous crystalline macroligand for well-defined molecular catalysts allows benefiting from molecular-scale understanding of interactions and mechanisms as well as from stabilization through site-isolation and recycling ability

Unravelling the molecular structure and confinement of an or-ganometallic catalyst heterogenized within amorphous porous polymers

The catalytic activity of multifunctional microporous materials is directly linked to the spatial arrangement of their struc-tural building blocks. Despite great achievements in the design and use of isolated catalytic sites within such materials, the precise determination of their atomic-level structure and their local environment still remains a fundamental chal-lenge, especially when they are hosted in non-crystalline solids. Here, we show that by combining NMR measurements with pair distribution function (PDF) analysis and computational chemistry, a very accurate picture of the organometallic Cp*Rh catalytic sites inside the cavity of porous organic polymers can be determined. Two microporous supports based on bipyridine and biphenyl motifs functionalized with NH2 or NO2 groups were considered. Making use of differential PDF, Dynamic Nuclear Polarization (DNP) enhanced solid-state NMR spectroscopy on 15N labelled–NH2 and –NO2 materi-als, and 129Xe NMR, the detailed structure of the heterogenized organometallic complex and its confinement within the amorphous porous organic polymers is revealed with a precision of 0.1 Å, fully matched by the computed models. While the same well-defined molecular structure is observed for the organometallic catalyst independently of the functionalisa-tion of the porous organic polymer, subtle changes are detected in the average ligand-pore wall distance and interactions in the two materials