CO conversion covers a wide range of possible application areas from fuels to bulk and commodity chemicals and even to specialty products with biological activity such as pharmaceuticals. In the present review, we discuss selected examples in these areas in a combined analysis of the state-of-the-art of synthetic methodologies and processes with their life cycle assessment. Thereby, we attempted to assess the potential to reduce the environmental footprint in these application fields relative to the current petrochemical value chain. This analysis and discussion differs significantly from a viewpoint on CO utilization as a measure for global CO mitigation. Whereas the latter focuses on reducing the end-of-pipe problem "CO emissions" from todays' industries, the approach taken here tries to identify opportunities by exploiting a novel feedstock that avoids the utilization of fossil resource in transition toward more sustainable future production. Thus, the motivation to develop CO-based chemistry does not depend primarily on the absolute amount of CO emissions that can be remediated by a single technology. Rather, CO-based chemistry is stimulated by the significance of the relative improvement in carbon balance and other critical factors defining the environmental impact of chemical production in all relevant sectors in accord with the principles of green chemistry.

The selective aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran has been performed under mild conditions at 80 °C and 20 bar of synthetic air in methyl t-butyl ether. Ru clusters supported on covalent triazine frameworks (CTFs) allowed excellent selectivity and superior catalytic activity compared to other support materials such as activated carbon, γ-Al2 O3 , hydrotalcite, or MgO. CTFs with varying pore size, specific surface area, and N content could be prepared from different monomers. The structural properties of the CTF materials influence the catalytic activity of Ru/CTF significantly in the aerobic oxidation of HMF, which emphasizes the superior activity of mesoporous CTFs. Recycling of the catalysts is challenging, but promising methods to maintain high catalytic activity were developed that facilitate only minor deactivation in five consecutive recycling experiments.

The quest for active, selective and stable catalysts for various applications has led researchers worldwide to investigate several combinations of molecular and solid catalyst systems. Solid molecular catalysts are considered to combine selectivity and reactivity of the molecular species with facile handling and good stability of the heterogeneous counterpart. Among other nanoporous polymers, covalent triazine‐based frameworks (CTFs) exhibit great potential as supports for both molecular as well as nanoparticulate species. Their high chemical and thermal stability in combination with tunable functionality to imbed active sites make them promising candidates to bridge the gap between homogeneous and heterogeneous catalysis. This Minireview seeks to outline the most recent developments in order to amplify research efforts within this fascinating and fast emerging field of material design and application. Emphasis is placed on the most recent advances in the following fields: Synthesis approaches and characteristics of CTFs, solid molecular catalysts and metal nanoparticles supported on CTFs as well as current challenges.

The base-free aqueous-phase oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxilic acid (FDCA) was performed at 140 °C and 20 bar of synthetic air as the oxidant. Ru clusters supported on covalent triazine frameworks (CTFs) enabled superior conversion (99.9%) and FDCA yields in comparison to other support materials such as activated carbon and γ-Al2O3 after only 1 h. The properties of the CTFs such as pore volume, specific surface area, and polarity could be tuned by using different monomers. These material properties influence the catalytic activity of Ru/CTF significantly as mesoporous CTFs showed superior activity compared to microporous materials, whereas high polarities provide further beneficial effects. The recyclability of the prepared Ru/CTF catalysts was comparable to that of Ru/C at high conversions and product yields. Nevertheless, minor deactivation in five successive recycling experiments was observed.

An electrocatalytic transformation of biomass based platform chemicals is feasible even using crude fermentation broth.