Victor Sans

3D-printed devices for continuous-flow organic chemistry

Summary We present a study in which the versatility of 3D-printing is combined with the processing advantages of flow chemistry for the synthesis of organic compounds. Robust and inexpensive 3D-printed reactionware devices are easily connected using standard fittings resulting in complex, custom-made flow systems, including multiple reactors in a series with in-line, real-time analysis using an ATR-IR flow cell. As a proof of concept, we utilized two types of organic reactions, imine syntheses and imine reductions, to show how different reactor configurations and substrates give different products.

Base supported ionic liquid-like phases as catalysts for the batch and continuous-flow Henry reaction

New solid basic catalysts immobilised onto supported ionic liquid-like phases have been prepared, having suitable mechanical stability for their use for the continuous-flow Henry reaction.

Assembly of a gigantic polyoxometalate cluster {W200Co8O660} in a networked reactor system.

A giant leap: A networked reactor system was used for the first time for the discovery and synthesis of new polyoxometalates, including the gigantic title system. The system comprises of three reactors connected in a triangular array with a central triply connected reactor. This system was used to screen multiple one-pot reactions and reaction variables for the automated syntheses of polyoxometalates.

Continuous parallel ESI-MS analysis of reactions carried out in a bespoke 3D printed device.

Summary Herein, we present an approach for the rapid, straightforward and economical preparation of a tailored reactor device using three-dimensional (3D) printing, which can be directly linked to a high-resolution electrospray ionisation mass spectrometer (ESI-MS) for real-time, in-line observations. To highlight the potential of the setup, supramolecular coordination chemistry was carried out in the device, with the product of the reactions being recorded continuously and in parallel by ESI-MS. Utilising in-house-programmed computer control, the reactant flow rates and order were carefully controlled and varied, with the changes in the pump inlets being mirrored by the recorded ESI-MS spectra.

Advanced reactor engineering with 3D printing for the continuous-flow synthesis of silver nanoparticles

The implementation of advanced reactor engineering concepts employing additive manufacturing is demonstrated. The design and manufacturing of miniaturised continuous flow oscillatory baffled reactors (mCOBR) employing low cost stereolithography based 3D printing is reported for the first time. Residence time distribution experiments have been employed to demonstrate that these small scale reactors offer improved mixing conditions at a millimetre scale, when compared to tubular reactors. Nearly monodisperse silver nanoparticles have been synthesised employing mCOBR, showing higher temporal stability and superior control over particle size distribution than tubular flow reactors.

Residence time distribution, a simple tool to understand the behaviour of polymeric mini-flow reactors

A simple method for the determination of the residence time distribution (RTD) of different polymer-based mini-flow reactors has been developed. The flow patterns have been adjusted employing the axial dispersion model, allowing a quantitative comparison of the flow patterns of the different structures. The use of different pulse tracer experiments highlights the differences in reactor behaviour depending on the nature (gel vs. macroporous) and shape (beads vs. monoliths) of the polymeric materials used in the reactor preparation. Thus, reactors based on monolithic columns showed a superior performance in terms of flow distribution when compared to commercial bead-shaped packed polymers of different sizes and backbone structure, confirming previous experimental results. These differences can help to understand the different catalytic efficiency detected for these mini-flow fixed-bed reactors. The model presented can help to properly design new processes based on the use of continuous flow reactors facilitated by functional materials, which is becoming an essential goal nowadays, in particular in the context of developing new efficient and clean technologies.

Redox-active organic–inorganic hybrid polyoxometalate micelles

A redox-active hybrid organic–inorganic polyoxometalate surfactant showed solvent-dependent self-assembly to form nano-scale architectures. The supramolecular assemblies exhibited contrasting electronic structure and redox activity to their molecular building units, and were found to be stable under electrochemical reduction and re-oxidation.

Non-equilibrium dynamic control of gold nanoparticle and hyper-branched nanogold assemblies

A flow system capable of dynamically controlling the synthesis of inorganic nanomaterials in real time switching between different conditions is presented whereby the combination of reactor engineering, ligand design and the employment of two in-line analytical techniques enables the synthesis and rapid characterisation of gold nanoparticles. Furthermore, it has been possible to discover a new type of hyper-branched nanogold-based material directly based on the optical feedback from UV-Vis, without stopping the process and the nanoparticles have been characterised using TEM.

Development of efficient processes under flow conditions based on catalysts immobilized onto monolithic supported ionic liquid-like phases*

The introduction of imidazolium subunits into polystyrene-divinylbenzene (PS-DVB) polymers enables the preparation of a variety of catalytic systems. Those include the stabilization of catalytically active Pd nanoparticles (PdNPs), immobilized enzymes, and basic catalysts. The use of monolithic supports having the appropriate morphological properties is greatly advantageous for the development of efficient catalytic processes under flow conditions based on those systems. On the other hand, the combination of those supported catalytic systems and flow conditions can be further implemented, in terms of green chemistry, by the substitution of the use of traditional solvents by environmentally friendly conditions such as the use of supercritical fluids (SCFs).

Orbital Engineering: Photoactivation of an Organofunctionalized Polyoxotungstate

Tungsten-based polyoxometalates (POMs) have been employed as UV-driven photo-catalysts for a range of organic transformations. Their photoactivity is dependent on electronic transitions between frontier orbitals and thus manipulation of orbital energy levels provides a promising means of extending their utility into the visible regime. Herein, an organic-inorganic hybrid polyoxometalate, K6 [P2 W17 O57 (PO5 H5 C7 )2 ]⋅6 C4 H9 NO, was found to exhibit enhanced redox behaviour and photochemistry compared to its purely inorganic counterparts. Hybridization with electron-withdrawing moieties was shown to tune the frontier orbital energy levels and reduce the HOMO-LUMO gap, leading to direct visible-light photoactivation of the hybrid and establishing a simple, cheap and effective approach to the generation of visible-light-activated hybrid nanomaterials.