Homoconjugation and Tautomeric Isomerism in Triptycene-Fused Pyridylbenzimidazoles

The facile, metal-free synthesis and characterization of three new series of triptycene-fused pyridylbenzimidazoles are reported; such compounds possess an imidazole moiety fused within the benzene rings of the trypticene and a pyridine ring installed at position 2 of the imidazole rings. The position of the nitrogen atom of the pyridyl moiety linked to position 2 of the fused benzimidazole scaffold is systematically changed from the ortho to para position. The number of substituted blades bearing the pyridyl-substituted fused benzimidazole scaffolds has been increased from one to three. Such a library of compounds allowed us to evaluate the enhancement of two main effects: tautomeric isomerism and homoconjugation. The characteristic dynamic equilibrium between different isomers induced by prototropic tautomerization was examined by 1H nuclear magnetic resonance spectroscopy. By comparison of the photophysical properties of the new compounds with those of classical planar pyridylbenzimidazoles, the presence of the homoconjugation effect between the different triptycene blades was demonstrated. Fine details of the electronic structure of the new derivatives were unraveled by a computational analysis. The novel compounds can be employed for the construction of intriguing self-assembled supramolecular architectures.

A Triptycene-Based 2D MOF with Vertically Extended Structure for Improving the Electrocatalytic Performance of CO2 to Methane

Two-dimensional conductive metal-organic frameworks (2D-c-MOFs) have attracted extensive attention owing to their unique structures and physical-chemical properties. However, the planarly extended structure of 2D-c-MOFs usually limited the accessibility of the active sites. Herein, we designed a triptycene-based 2D vertically conductive MOF (2D-vc-MOF) by coordinating 2,3,6,7,14,15-hexahydroxyltriptycene (HHTC) with Cu²⁺ . The vertically extended 2D-vc-MOF(Cu) possesses a weak interlayer interaction, which leads to a facile exfoliation to the nanosheet. Compared with the classical 2D-c-MOFs with planarly extended 2D structures, 2D-vc-MOF(Cu) exhibits a 100 % increased catalytic activity in terms of turnover number and a two-fold increased selectivity. Density functional theory (DFT) calculations further revealed that higher activity originated from the lower energy barriers of the vertically extended 2D structures during the CO₂ reduction reaction process.

Molecular Cavity for Catalysis and Formation of Metal Nanoparticles for Use in Catalysis

The employment of weak intermolecular interactions in supramolecular chemistry offers an alternative approach to project artificial chemical environments like the active sites of enzymes. Discrete molecular architectures with defined shapes and geometries have become a revolutionary field of research in recent years because of their intrinsic porosity and ease of synthesis using dynamic non-covalent/covalent interactions. Several porous molecular cages have been constructed from simple building blocks by self-assembly, which undergoes many self-correction processes to form the final architecture. These supramolecular systems have been developed to demonstrate numerous applications, such as guest stabilization, drug delivery, catalysis, smart materials, and many other related fields. In this respect, catalysis in confined nanospaces using such supramolecular cages has seen significant growth over the years. These porous discrete cages contain suitable apertures for easy intake of substrates and smooth release of products to exhibit exceptional catalytic efficacy. This review highlights recent advancements in catalytic activity influenced by the nanocavities of hydrogen-bonded cages, metal-ligand coordination cages, and dynamic or reversible covalently bonded organic cages in different solvent media. Synthetic strategies for these three types of supramolecular systems are discussed briefly and follow similar and simplistic approaches manifested by simple starting materials and benign conditions. These examples demonstrate the progress of various functionalized molecular cages for specific chemical transformations in aqueous and nonaqueous media. Finally, we discuss the enduring challenges related to porous cage compounds that need to be overcome for further developments in this field of work.

Pd nanoparticle growth monitored by DRIFT spectroscopy of adsorbed CO

Synchrotron-based X-ray absorption spectroscopy and scattering are known in situ probes of metal nanoparticles (NPs). A limited number of laboratory techniques allow post-synthesis diagnostics of the active metal surface area. This work demonstrates the high potential of infrared spectroscopy as an in situ laboratory probe for the growth of metal NPs on a substrate. We introduce a small fraction of CO molecules into the reaction mixture as a probe to monitor the reduction kinetics of the Pd2+ precursor on ceria in hydrogen.

Shape-persistent porous organic cage supported palladium nanoparticles as heterogeneous catalytic materials

Porous Organic Cages (POCs) are an emerging class of self-assembling, porous materials with novel properties. They offer a key advantage over other porous materials in permitting facile solution processing and re-assembly. The combination of POCs with metal nanoparticles (NPs) unlocks applications in the area of catalysis. In this context, POCs can function as both the template of ultra-small NPs and a porous, but reprocessable, heterogeneous catalyst support. Here, we demonstrate the synthesis of ultra-small Pd NPs with an imine linked POC known as 'CC3', and show that hydrogen gas can be used to form metallic NPs at ∼200 °C without the reduction of the organic cage (and the accompanying, unwanted loss of crystallinity). The resulting materials are characterized using a range of techniques (including powder diffraction, scanning transmission electron microscopy and synchrotron X-ray absorption spectroscopy) and shown to be recrystallizable following dissolution in organic solvent. Their catalytic efficacy is demonstrated using the widely studied carbon monoxide oxidation reaction. This demonstration paves the way for using ultra-small NPs synthesized with POCs as solution-processable, self-assembling porous catalytic materials.

A porous triptycene-based covalent polymer stabilized binary metal sulfide for enhanced hydrogen evolution under visible light

A novel triptycene-based covalent polymer (TCP) with a high surface area was constructed through the Suzuki coupling reaction.

Bactericidal and catalytic performance of green nanocomposite based-on chitosan/carbon black fiber supported monometallic and bimetallic nanoparticles

Nanoparticles were synthesized on the surface of green nanocomposite based on carbon black dispersed in chitosan (CB-CS) fibres. The nanoparticles were monometallic Co, Ag and Cu and bimetallic Co + Cu and Co + Ag. The CB-CS fibres were prepared and introduced into separate metal salt solutions containing Co²⁺, Ag⁺ and Cu²⁺ and mixed Co²⁺+Cu²⁺ and Co²⁺+Ag⁺ ions. The metal ions immobilized on the surface of CB-CS were reduced using sodium borohydride (NaBH₄) as reducing agent to synthesize the corresponding zero-valent metal nanoparticles-loaded CB-CS fibres. All the nanoparticles-loaded CB-CS samples were characterized using field emission-scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction techniques. When tested as catalysts, the nanoparticles-loaded CB-CS showed excellent catalytic ability for the reduction of toxic and environmentally unwanted pollutants of para-nitrophenol, congo red and methyl orange dyes. Afterwards, the antimicrobial activities of virgin and metal-loaded CB-CS fibres were tested and the metal-loaded CB-CS fibres were found to be effective against Escherichia coli. In addition, the catalyst can be recovered easily by simply removing the fibres from the reaction mixture and can be recycled several times while maintaining high catalytic efficiency.

Promotion effect of oxygen-containing functional groups and Fe species on Pd@graphene for CO catalytic oxidation

Catalysts using graphene as a support possessed higher catalytic activity and stability.

Gold nanoparticles encapsulated in hierarchical porous polycarbazole: preparation and application in catalytic reduction

AuNPs/porous polycarbazole composites with hierarchical pores exhibit high porosity and efficient catalytic reduction.

Direct arylation of fluoroarenes toward linear, bent-shaped and branched π-conjugated polymers: polycondensation post-polymerization approaches

A direct arylation polycondensation of fluoroarenes with 2,7-dibromo-9,9-dioctylfluorene,F8, was achieved in a low polar solvent, toluene.

A hydroxyl-functionalized microporous organic polymer for capture and catalytic conversion of CO2

A novel hydroxyl-functionalized microporous organic polymer (HF-MOP) exhibited good CO₂ capture performance and excellent catalytic activity in cycloaddition reaction.

Pd loaded amphiphilic COF as catalyst for multi-fold Heck reactions, C-C couplings and CO oxidation

COFs represent a class of polymers with designable crystalline structures capable of interacting with active metal nanoparticles to form excellent heterogeneous catalysts. Many valuable ligands/monomers employed in making coordination/organic polymers are prepared via Heck and C-C couplings. Here, we report an amphiphilic triazine COF and the facile single-step loading of Pd⁰ nanoparticles into it. An 18–20% nano-Pd loading gives highly active composite working in open air at low concentrations (Conc. Pd(0) <0.05 mol%, average TON 1500) catalyzing simultaneous multiple site Heck couplings and C-C couplings using ‘non-boronic acid’ substrates, and exhibits good recyclability with no sign of catalyst leaching. As an oxidation catalyst, it shows 100% conversion of CO to CO₂ at 150 °C with no loss of activity with time and between cycles. Both vapor sorptions and contact angle measurements confirm the amphiphilic character of the COF. DFT-TB studies showed the presence of Pd-triazine and Pd-Schiff bond interactions as being favorable.

Ultrasensitive biosensing platform based on the luminescence quenching ability of plasmonic palladium nanoparticles

An ultrasensitive biosensing platform for DNA and protein detection is constructed based on the luminescence quenching ability of plasmonic palladium nanoparticles (PdNPs). By growing the particles into large sizes (ca. 30 nm), the plasmonic light absorption of PdNPs is broadened and extended to the visible range with extinction coefficients as high as 10(9)  L mol(-1)  cm(-1) , enabling complete quenching of fluorescent dyes that emit at diverse ranges and that are tagged to bioprobes. Meanwhile the nonspecific quenching of the dyes (not bound to probes) is negligible, leading to extremely low background signal. Utilizing the affinity of PdNPs towards bioprobes, such as single-stranded (ss) DNA and polypeptide molecules, which is mainly assigned to the coordination interaction, nucleic acid assays with a quantification limit of 3 pM target DNA and protein assay are achieved with a simple mix-and-detect strategy based on the luminescence quenching-and-recovery protocol. This is the first demonstration of biosensing employing plasmonic absorption of nanopalladium, which offers pronounced sensing performances and can be reasonably expected for wide applications.

Controlled synthesis of Pd and Pd–Au nanoparticles: effect of organic amine and silanol groups on morphology and polycrystallinity of nanomaterials

New process for 3-APTMS and organic reducing agent mediated synthesis of amphiphilic PdNPs, Pd-Au/Au-Pd justifying specific interaction of silanol with PdNPs controlling polycrystallinity, nanogeometry, morphology and functionality.

Preparation of a microporous organic polymer by the thiol–yne addition reaction and formation of Au nanoparticles inside the polymer

We prepared an Au NP loaded microporous polymer using the thiol–yne reaction and in situ reduction reaction, and investigated its catalytic activity.

CdS-decorated triptycene-based polymer: durable photocatalysts for hydrogen production under visible-light irradiation

Nanocomposites formed by CdS with porous triptycene-based polymers are effective catalysts for photocatalytic hydrogen production.

Fabrication of porous organic polymers in the form of powder, soluble in organic solvents and nanoparticles: a unique platform for gas adsorption and efficient chemosensing

Tetraphenyl-5,5-dioctylcyclopentadiene based porous organic polymers were fabricated in the form of powder, soluble in organic solvents and nanoparticles and were explored for gas adsorption and chemosensing.

Facile fabrication of ultrafine palladium nanoparticles with size- and location-control in click-based porous organic polymers

Two click-based porous organic polymers (CPP-1 and CPP-2) are readily synthesized through a click reaction. Using CPP-1 and CPP-2 as supports, palladium nanoparticles (NPs) with uniform and dual distributions were prepared through H2 and NaBH4 reduction routes, respectively. Ultrafine palladium NPs are effectively immobilized in the interior cavities of polymers. The coordination of 1,2,3-triazolyl to palladium and the confinement effect of polymers on palladium NPs are verified by solid-state (13)C NMR and IR spectra, XPS analyses, EDX mapping, and computational calculation. The steric and electronic properties of polymers have a considerable influence on the interaction between polymers and palladium NPs, as well as the catalytic performances of NPs. The ultrafine palladium NPs with uniform distribution exhibit superior stability and recyclability over palladium NPs with dual distributions and palladium on charcoal in the hydrogenation of nitroarenes, and no obvious agglomeration and loss of catalytic activity were observed after recycling several times. The excellent performances mainly result from synergetic effects between palladium NPs and polymers.

Enzymes as bionanoreactors: glucose oxidase for the synthesis of catalytic Au nanoparticles and Au nanoparticle–polyaniline nanocomposites

Biogenic synthesis of Au nanoparticles and Au nanoparticle–polyaniline composite could be accomplished taking advantage of the reducing and catalytic activity of glucose oxidase.

Designing a yolk–shell type porous organic network using a phenyl modified template

A new strategy was developed to introduce gold nanoparticles into yolk–shell type porous organic networks under the assistance of a phenyl modified template.

Redox-active conjugated microporous polymers: a new organic platform for highly efficient energy storage

Redox-active conjugated microporous polymers offer outstanding energy storage in lithium batteries via synergistic structural effects.

In situ formation of well-dispersed palladium nanoparticles immobilized in imidazolium-based organic ionic polymers

A new strategy for the synthesis of well-dispersed palladium nanoparticles (NPs) immobilized in imidazolium-based porous organic ionic polymers was presented in this study. The as-synthesized polymers showed excellent catalytic activity and reusability in the hydrogenation of nitroarenes without extra addition of palladium species.