Francis Verpoort

Metal–organic frameworks: versatile heterogeneous catalysts for efficient catalytic organic transformations

Novel catalytic materials are highly demanded to perform a variety of catalytic organic reactions. MOFs combine the benefits of heterogeneous catalysis like easy post reaction separation, catalyst reusability, high stability and homogeneous catalysis such as high efficiency, selectivity, controllability and mild reaction conditions. The possible organization of active centers like metallic nodes, organic linkers, and their chemical synthetic functionalization on the nanoscale shows potential to build up MOFs particularly modified for catalytic challenges. In this review, we have summarized the recent research progress in heterogeneous catalysis by MOFs and their catalytic behavior in various organic reactions, highlighting the key features of MOFs as catalysts based on the active sites in the framework. Examples of their post functionalization, inclusion of active guest species and metal nanoparticles have been discussed. Finally, the use of MOFs as catalysts for asymmetric heterogeneous catalysis and stability of MOFs has been presented as separate sections.

Applications of Raman spectroscopy in pharmaceutical analysis

As Raman spectroscopy enables rapid, non-destructive measurements, the technique appears a most promising tool for on-line process monitoring and analysis in the pharmaceutical industry. This article gives a short introduction to Raman spectroscopy and presents several applications in the pharmaceutical field.

Ruthenium-based olefin metathesis catalysts derived from alkynes.

Department of Inorganic and Physical Chemistry, Laboratory of Organometallic Chemistry and Catalysis, Ghent University, Krijgslaan 281 (S-3), 9000 Ghent, Belgium, Liaoning Provincial Key Laboratory for Green Synthesis and Preparative Chemistry of Advanced Materials, Liaoning University, Shenyang 110036, People’s Republic of China, and College of Chemistry, Liaoning University, Shenyang 110036, People’s Republic of China

Latent olefin metathesis catalysts

Olefin metathesis is a versatile synthetic tool for the redistribution of alkylidene fragments at carbon-carbon double bonds. This field, and more specifically the development of task-specific, latent catalysts, attracts emerging industrial and academic interest. This tutorial review aims to provide the reader with a concise overview of early breakthroughs and recent key developments in the endeavor to develop latent olefin metathesis catalysts, and to illustrate their use by prominent examples from the literature.

Metal–organic molecular cages: applications of biochemical implications

New well-designed materials are highly demanded with the prospect of versatile properties, offering successful applications as alternates to conventional materials. Major new insights into metal-organic self-assembled structures assisting biochemical purposes have recently emerged. Metal-organic polyhedral cages are highlighted as new research materials to be used for therapeutic, sensing and imaging, purposes etc. This tutorial review covers achievements in the biochemical applications of these multinuclear complexes. Examples of their ability to aid the ionic transport, biomolecular sensing, imaging, and drug delivery are presented.

Heterogeneous tungsten-based catalysts for the epoxidation of bulky olefins

This paper discusses the design of different W and PW heterogeneous catalysts. The first part focuses on the electrostatic immobilization of those species on organic resins. In the second part, some new silica materials are synthesized as carrier materials for PW species. Both electrostatic immobilization and covalent linking of the species on the modified silica materials are discussed. Besides a thorough spectroscopic study (FT-IR, Raman, NMR, TGA and EPMA), the catalytic properties of the designed catalysts are evaluated for the epoxidation of a variety of bulky olefins.

Immobilization of multifunctional Schiff base containing ruthenium complexes on MCM-41

Abstract Two solid catalysts in which a Schiff base containing ruthenium complex has been covalently anchored on MCM-41 have been prepared and characterized. The catalytic behavior of these materials in ring-closing metathesis (RCM), ring-opening metathesis polymerization (ROMP), Kharasch addition, atom transfer radical polymerization (ATRP) and vinylation reactions as well as the recycling characteristics in RCM reactions are presented to exemplify the effectiveness and the multifunctional character of these catalytic systems. For ROMP the influence of the polymerization solvent on the performance of the catalysts was checked. For the RCM reactions both reaction time and reaction temperature were varied in order to determine the influence of these parameters on the RCM activity of our catalysts. The activity of our catalytic systems in radical reactions such as ATRP and the Kharasch addition is promising. Our results demonstrate that the ATRP process of styrene proceeds in a controlled fashion allowing the synthesis of well-defined polymers. Furthermore, we were able to demonstrate that the Kharasch activity of our catalysts shows a pronounced temperature dependence. In addition to all this, we also postulated a mechanism that explains for the observed selectivities in the vinylation experiments. The host–guest interaction of these hybrid catalytic systems is studied by XRD, XRF, ICP/MS, BET, FT-Raman and solid state NMR analysis.

Assessing the scope of the introduction of Schiff bases as co-ligands for monometallic and homobimetallic ruthenium ring-opening metathesis polymerisation and ring-closing metathesis initiators.

A new class of homobimetallic and monometallic Schiff base-substituted ruthenium olefin metathesis catalysts has been prepared, characterised and tested in ring-closing metathesis (RCM) and ring-opening metathesis polymerisation (ROMP) reactions. The results obtained point out that the synergy of Schiff base ligands with coordinatively labile ligands leads to bimetallic catalytic systems that combine very high activity with excellent stability. Furthermore, the catalytic activity of these catalysts is very dependent on the steric and electronic environment of the Schiff base. To conclude, a mechanism that explains the obtained data is postulated.

ROMP and RCM catalysed by (R3P)2Cl2RuCHPh immobilised on a mesoporous support

Heterogeneous hybrid catalysts with respect to the metathesis of olefins have been prepared by ligand exchange reaction between Ru-alkylidene complexes (Grubbs’ type) and a phosphinated mesoporous matrix (P-MCM-41). The host/guest interaction is studied by FT-Raman, thermogravimetric analysis and N2 adsorption. Catalytic tests in olefin metathesis reveal ROMP activity towards norbornene, even in aquatic environment, and a very high activity for the RCM of diallylamine and diethyldiallylmalonate.

A heterogeneous Ru–hydroxyapatite catalyst for mild racemization of alcohols

Racemization of chirally stable secondary alcohols was performed using a truly heterogeneous catalyst under mild reaction conditions in the absence of any additive or cocatalyst. The catalyst is based on Ru3+ immobilized on calcium hydroxyapatite (Ru–HAP). The preparation of the calcium hydroxyapatite (HAP) support and the Ru content and immobilization were optimized leading to maximal catalytic performance. Via combined XRD, Raman, SEM, XPS, EPR, N2 adsorption, and ICP analysis, information on both the compositional and the structural properties of the material was obtained. The Ru–HAP catalyst is able to racemize benzylic as well as aliphatic secondary alcohols. The catalyst scope was further investigated for racemization of several mono- and polyfunctional secondary alcohols. Performing standard racemization of a reference substrate in the presence of a functional additive demonstrated the inhibitory effect of some of these functions. Finally the heterogeneous nature of the catalyst was verified by filtrate tests.