Formic acid is a main product from biomass-derived carbohydrates and is attracting ever more attention as a hydrogen source for a sustainable chemical production.

Flow chemistry has changed chemical process designs toward process intensification and is generally considered as green methodology. In this connection, this perspective provides a more critical and holistic view about the sustainability of flow chemistry by introducing both simple and complex holistic tools for environmental quantitative assessment on sustainability and providing examples of how they were used for flow chemistry. The latter also shows a critical assessment of what flow chemistry can add to make chemical processes more sustainable. With the increasing complexity of assessment, green chemistry metrics, life cycle assessment methodology, and circular transition indicators are discussed. In this way, the sustainability of flow chemistry is assessed first on the level of a reaction only and then moving to a process level and beyond. Flow chemists are very aware of the principles of green chemistry and their simple metrics. Yet, they hardly use life cycle assessment, and quantitative circularity analysis has not been made. When those assessments are used, it is usually done by researchers with an ecology background. This perspective aims to make flow chemists aware of the opportunities that complex environmental assessment can provide and that protecting our planet requires a holistic sustainability consideration. The perspective critically states what each of the three types of assessments can do and what their limitations are.

A new polystyrene-type resin loaded with pincer-type imidazolium ionic tag has been very effective in the immobilization of [PdCl4]2− palladium complex leading to a very low leaching of the metal during its use in flow.

A resin-bound 1,2,4-triazolium ionic tag has been used as support for the preparation of solid palladium nanoparticles (Pd(0)-POLI-TAG-Pd). Owing to the pincer-type architecture of the triazolium ligand, the stabilization of a high amount of palladium nanoparticles (16 wt %) has been possible. The catalytic system has been fully characterized and used in low amounts (i.e., 0.1 mol % palladium loading) in representative Heck–Mizoroki cross-coupling processes. A negligible release of the metal was demonstrated, and a high activity was obtained over more runs. Besides, the protocol has been optimized for the use of safe biomass-derived γ-valerolactone reaction medium.

Herein, we disclose the first C–2-selective C–H alkenylation of quinoline N–oxides catalyzed by a heterogeneous palladium catalyst. The protocol does not require the use of an external oxidant and it...

Herein, we report the development of a tailor-made fluoride-based heterogeneous catalyst, POLITAG-F, for the waste-minimized continuous production of cyanohydrin silyl ethers. The careful designing of the polymeric support and the choice of fluoride ion as the anionic species resulted in the improvement of catalytic efficiency and allowed the effective conversion of different carbonyls (aldehydes, ketones, and unsaturated ketones). The POLITAG-F catalyst, employed under flow conditions, led to the conversion of large amounts (over 100 mmol) of the substrate with a productivity of 0.1 mmol min–1. In addition, flow conditions allowed to minimize the waste production reaching an associated E-factor value of 0.04. An exhaustive evaluation of the environmental impact of our protocol has been reported by considering several green metrics (process mass intensity, atom economy, and reaction mass efficiency) and also the benign index and the safety hazard index of the process.

The use of hydrogen at high-pressure is associated with major safety concerns, storage, and high cost. Therefore, the development of reductive chemical processes based on the use of low-pressure hydrogen is very attractive in view of an industrial-scale application. This perspective focuses on the most representative studies reported until 2021 dealing with the reductive manipulation processes of diverse biomass-based feedstock utilizing alternative liquid organic hydrogen carriers (LOHCs). In this context, the research has been dedicated mainly to formic acid and small molecular alcohols, specifically isopropanol. The perspective illustrates the transformations of biobased platform molecules, such as levulinic acid, furfural, and 5-hydroxymethylfurfural, into valuable products, including biofuels. In addition, the lignin upgrading mediated by these H2 sources is discussed.

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