A boost to chemical catalysis
Microfluidics is a discipline that explores the behaviour and control of fluids that are constrained to the sub-millimetre scale. The field is at the crossroads of biotechnology, chemistry, engineering and physics. The EU-funded project 'Application of Droplet-Based Microfluidics for the Screening of Supramolecular Catalysts' (MicroDropCat) developed new ways to prepare and screen homogeneous catalysts. These catalysts are important as they are used to create a sequence of reactions in chemical experiments. The method is based on supramolecular or self-assembled ligands using droplet-based microfluidics. Currently, the process of discovering and preparing homogeneous catalysts requires a lot of time, implying a need for more efficient methodology. To use chemistry-related terminology, in order to discover effective ligands, this constraint can be overcome through supramolecular self-assembly of ligands through reversible non-covalent interactions. To achieve its aims, and backed by solid knowledge in microfluidics, chemical engineering and spectroscopy, the project team merged different arrays of nanolitre-sized droplets containing complementary ligands. The droplets were then merged with a transition metal precursor to generate 'catalytic microdroplets' that were subsequently combined with reactants in reaction-size vessels on the nanolitre scale. This intricate process enabled the evaluation of catalytic activity related to the self-assembly process, finally yielding the required level of catalysts. The experiments markedly increased the potential chemical space within which an optimal ligand set can be found. While some of the experiments were set back by synthesis and screening techniques that rely on the macroscale, reactions were sped up by significantly miniaturising the reaction vessel. In the near future, the project team will publish results on the novel catalytic system that will be used in developing a more efficient microfluidic device. The basic scientific and technical solutions for this ambitious initiative have been laid out and will serve as a good basis for realising this 'catalyst-making' device.
