Water dispersible surface-functionalized platinum/carbon nanorattles for size-selective catalysis

MOFganic Chemistry: Challenges and Opportunities for Metal-Organic Frameworks in Synthetic Organic Chemistry

Metal-organic frameworks (MOFs) are porous, crystalline solids constructed from organic linkers and inorganic nodes that have been widely studied for applications in gas storage, chemical separations, and drug delivery. Owing to their highly modular structures and tunable pore environments, we propose that MOFs have significant untapped potential as catalysts and reagents relevant to the synthesis of next-generation therapeutics. Herein, we outline the properties of MOFs that make them promising for applications in synthetic organic chemistry, including new reactivity and selectivity, enhanced robustness, and user-friendly preparation. In addition, we outline the challenges facing the field and propose new directions to maximize the utility of MOFs for drug synthesis. This perspective aims to bring together the organic and MOF communities to develop new heterogeneous platforms capable of achieving synthetic transformations that cannot be replicated by homogeneous systems.

Pillar[5]arene-Integrated Three-Dimensional Framework Polymers for Macrocycle-Induced Size-Selective Catalysis

Size-selective catalysis is of key importance in the conversion of crude oil or biomass. Here, we fabricate three pillar[5]arene-integrated porous organic polymers with three-dimensional (3D) network structures using 3D cross-linkers. The resulting polymers possess a high surface-to-mass ratio and exhibit exceptional size-selective catalysis in Knoevenagel condensation reactions. In addition, a mechanistic study indicates that the size-selective catalysis is due to the host-guest interaction between pillar[5]arene and substrates. This study suggests that macrocycle-containing polymers could be a promising candidate for size-selective catalysis.

A Mini Review on Yolk-Shell Structured Nanocatalysts

Yolk-shell structured nanomaterials, possessing a hollow shell and interior core, are emerging as unique nanomaterials with applications ranging from material science, biology, and chemistry. In particular, the scaffold yolk-shell structure shows great promise as a nanocatalyst. Specifically, the hollow shell offers a confined space, which keeps the active yolk from aggregation and deactivation. The inner void ensures the pathway for mass transfer. Over the last few decades, many strategies have been developed to endow yolk-shell based nanomaterials with superior catalytic performance. This minireview describes synthetic methods for the preparation of various yolk-shell nanomaterials. It discusses strategies to improve the performance of yolk-shell catalysts with examples for engineering the shell, yolk, void, and related synergistic effects. Finally, it considers the challenges and prospects for yolk-shell nanocatalysts.

Catalytic resonance theory: parallel reaction pathway control

Catalytic enhancement of chemical reactions via heterogeneous materials occurs through stabilization of transition states at designed active sites, but dramatically greater rate acceleration on that same active site can be achieved when the surface intermediates oscillate in binding energy. The applied oscillation amplitude and frequency can accelerate reactions orders of magnitude above the catalytic rates of static systems, provided the active site dynamics are tuned to the natural frequencies of the surface chemistry. In this work, differences in the characteristics of parallel reactions are exploited via selective application of active site dynamics (0 < ΔU < 1.0 eV amplitude, 10⁻⁶ < f < 10⁴ Hz frequency) to control the extent of competing reactions occurring on the shared catalytic surface. Simulation of multiple parallel reaction systems with broad range of variation in chemical parameters revealed that parallel chemistries are highly tunable in selectivity between either pure product, even when specific products are not selectively produced under static conditions. Two mechanisms leading to dynamic selectivity control were identified: (i) surface thermodynamic control of one product species under strong binding conditions, or (ii) catalytic resonance of the kinetics of one reaction over the other. These dynamic parallel pathway control strategies applied to a host of simulated chemical conditions indicate significant potential for improving the catalytic performance of many important industrial chemical reactions beyond their existing static performance.

Branched catalytic reaction networks with oscillating chemical pathways perfectly select for reaction products at varying frequency.

Functionalization of Silk with In-Situ Synthesized Platinum Nanoparticles

After platinum nanoparticles (PtNPs) were in-situ synthesized on silk fabrics through heat treatment, it was determined that the treatment of the silk fabrics with PtNPs imparted multiple functions, including coloring, catalysis, and antibacterial activity. The formation of PtNPs on fabrics was affected by the Pt ion concentration, pH value of solution, and reaction temperature. Acidic condition and high temperature were found to facilitate the formation of PtNPs on silk. The color strength of silk fabrics increased with the concentration of Pt ions. The PtNP treated silk fabrics exhibited reasonably good washing color fastness and excellent rubbing color fastness. The morphologies and chemical components of the treated silk fabrics were analyzed using scanning electron microscopy and X-ray photoelectron spectroscopy. The PtNP treated silk fabric exhibited significant catalytic function and a notable antibacterial effect against Escherichia coli (E. coli).