Immobilization of an Iridium Pincer Complex in a Microporous Polymer for Application in Room-Temperature Gas Phase Catalysis

New insights for valorization of polyolefins/light alkanes: catalytic dehydrogenation of n-alkanes by immobilized pincer-iridium complexes

This scientific review delves into the innovative realm of polyolefins/light alkanes valorization through their catalytic dehydrogenation employing pincer-ligated iridium organometallic complexes. These widely studied catalysts exhibit outstanding properties, although the intrinsic characteristics of homogeneous catalysis (such as challenging product-catalyst separation, poor applicability to continuous-flow processes and low recyclability) limit their activity and industrial application, as well as their thermal stability. Through the immobilization of complexes on inorganic supports, these downsides have been bypassed, harnessing the true potential of these catalysts, affording more selective and stable catalysts in addition to facilitating their implementation in industrial processes. The findings described herein contribute to the advancement in the understanding of catalytic processes in hydrocarbon transformations, offering promising avenues for sustainable and selective production of valuable chemical intermediates from readily available feedstocks.

Ligating Catalytically Active Peptides onto Microporous Polymers: A General Route Toward Specifically-Functional High Surface Area Platforms

A versatile post-synthetic modification strategy to functionalize a high surface area microporous network (MPN-OH) by bio-orthogonal inverse electron-demand Diels-Alder (IEDDA) ligation is presented. While the polymer matrix is modified with a readily accessible norbornene isocyanate (Nor-NCO), a series of functional units presenting the robust asymmetric 1,2,4,5-tetrazine (Tz) allows easy functionalization of the MPN by chemoselective Nor/Tz ligation. A generic route is demonstrated, modulating the internal interfaces by introducing carboxylates, amides or amino acids as well as an oligopeptide d-Pro-Pro-Glu organocatalyst. The MPN-Pz-Peptide construct largely retains the catalytic activity and selectivity in an enantioselective enamine catalysis, demonstrates remarkable availability in different solvents, offers heterogeneous organocatalysis in bulk and shows stability in recycling settings.

Assembled Organoruthenium(II) for Formaldehyde Decomposition and Hydrogen Production

Formaldehyde decomposition is not only an attractive method for hydrogen production, but also a potential approach for gaseous formaldehyde removal. In this research, we prepare some assembled organoruthenium through coordination reaction between Ru(p-Cymene)Cl₂ and bridge-linking ligands. It is a creative approach for Ru(p-Cymene)Cl₂ conversion into heterogeneous particles. The rigidity of bridge-linking ligand enables assembled organoruthenium to have highly ordered crystalline structure, even show clear crystal lattice with spacing of 0.19 nm. XPS shows the N-Ru bond are formed between bridge-linking ligand and Ru(p-Cymene)Cl₂ . The assembled organoruthenium has high abundant active sites for formaldehyde decomposition at low temperature. The reaction rate could increase linearly with temperature and formaldehyde concentration, with a TOF of 2420 h^-1 at 90 °C. It is promising for gaseous formaldehyde decomposition in wet air or nitrogen. Formaldehyde conversion is up to 95 % over Ru-DAPM is 4,4'-diaminodiphenylmethane at 90 °C in air. Gaseous formaldehyde decomposition is a two-steps process under oxygen-free condition. Firstly, formaldehyde dissolve in water, and be converted into hydrogen and formic acid through formaldehyde-water shift reaction. Then intermediate formic acid will further decompose into hydrogen and carbon dioxide. We also find formaldehyde decomposition is a synergetic catalysis process of oxygen and water in moist air. Oxygen is conducive to formic acid desorption and decomposition on the active sites, so assembled organoruthenium exhibit slightly higher conversion for formaldehyde decomposition in moist air. This work proposes a distinctive method for gaseous formaldehyde decomposition in the air, which is entirely different from formaldehyde photocatalysis or thermocatalysis oxidation.

Well-Defined, Silica-Supported Homobimetallic Nickel Hydride Hydrogenation Catalyst

There is an increasing interest to replace precious metal-based catalysts by earth-abundant nonprecious metals due to higher costs, toxicity, and declining availability of the former. Here, the synthesis of a well-defined supported nickel hydrogenation catalyst prepared by surface organometallic chemistry is reported. For this purpose, [LNi(μ-H)]₂ (L = HC(CMeNC₆H₃(ⁱPr)₂)₂) was grafted on partially dehydroxylated silica to give a homobimetallic H- and O(silica)-bridged Ni₂ complex. The structure of the latter was confirmed by infrared spectroscopy, X-ray absorption near-edge structure, and extended X-ray absorption fine structure analyses as well as hydride titration studies. The immobilized catalyst was capable of hydrogenating alkenes and alkynes at low temperatures without prior activation. As an example, ethene can be hydrogenated with an initial turnover frequency of 25.5 min^-1 at room temperature.