MTCiting: Catalysis in Academic R&D

October 2025

In this edition of MTCiting, we dive into the latest published research on catalysis applications in academic R&D. Join us as we examine groundbreaking research that improves process safety and efficiency and contributes to sustainability in chemical manufacturing.

chemist using polymer chemistry for chemical based research and development

Catalytic PET Recycling – Effect of Water

Recovering the monomer bis(2-hydroxyethyl) terephthalate (BHET) from glycolysis of polyethylene terephthalate (PET) is important since the recovered monomer can be used for future PET production. However, any water present in the glycolysis process as an impurity or side product has an important, yet poorly understood role. The researchers comment that water could have dual effects on the glycolysis in that trace amounts could enhance catalyst activity and larger levels could hydrolyze ester bonds thus altering reaction pathways or deactivating catalysts. In this work, HPLC and in-situ FTIR measurements are used to determine product distribution and reaction kinetics on PET glycolysis as a function of water content (0–22.2 vol%), using heterogeneous catalysts (ZnO and Mn₂O₃) and homogeneous catalysts (zinc acetate (ZnAc₂), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)).

The researchers determine that despite the presence of high levels of water, the metal-based catalysts, ZnO, Mn₂O₃, retained high PET conversion levels, however, increased water content level caused a substantial drop in yield and selectivity of BHET. They explain that water acts as a competing nucleophile, promoting the hydrolysis of PET and the production of byproducts. Furthermore, they determined that the organic base catalysts TBD and DBU were highly susceptible to deactivation by water, evidenced by a significant decline in PET conversion and BHET yield with increasing water content. ReactIR measurements revealed that the presence of water significantly reduced the intensity of the C=N absorbance band, indicating protonation had occurred and deactivation of the catalyst. For organic bases, the negative effect of water is a reduction in catalytic activity, and not simply a change in the selectivity.

The authors conclude that this work demonstrates the importance of understanding the effect of water on catalyst- based PET glycolysis in order to design more water-tolerant catalysts for producing high-purity BHET.

Jia, Z., Zhang, J., Gao, L., Qin, L., Sun, H., Chen, J., & Yin, J. (2025). Unraveling the role of water on catalytic glycolysis of PET. RSC Sustainability. https://doi.org/10.1039/d5su00528k

General reaction scheme for an Iron-catalyzed cross-coupling of a substituted sp 3 carbon compound with a secondary amine to synthesize a tetrasubstituted carbon center.

Iron Catalysts with Soft Nucleophiles

There is great interest in using earth abundant, inexpensive metals such as iron as a catalyst. Cross-coupling reactions that use iron to couple alkyl or aryl electrophiles with a hard nucleophile organometallic reagent such as a Grignard reagent are frequently used in C–C formation. The researchers in this work explored whether iron could be used as a catalyst in the challenging coupling of C(sp³)–halide electrophiles with soft sulfur nucleophiles. This led to the successful development of cross-coupling reactions catalyzed by iron between benzyl or tertiary halides and soft nucleophiles such as thiols, alcohols, or amine nucleophiles. The use of hindered tertiary alkyl halides mitigates the benzylic substrate limitation. They comment that the system can be used for C–S, C–O, and C–N bond construction and the broad scope of these reactions resulted in a library of herbicide analogues and synthesis of hindered thioether, ether, and amine products.

Results from mechanistic experiments are consistent with a stereocenter-eliminating pathway that likely involves an organic radical intermediate. Combined in-situ ReactIR monitoring and interconversion experiments collectively support the existence of two separate reaction mechanisms that occur when benzyl or tertiary alkyl halides are coupled with either a thiol or disulfide coupling partner. This is supported by observing that the level of thiol-to-disulfide conversion is insufficient to account for the observed yields.

Semenya, J., Yang, Y., Lee, H. J., Giannantonio, K. A., Manduva, R., & Picazo, E. (2025). C(sp3)–heteroatom bond formation by iron-catalyzed soft couplings. Communications Chemistry, 8(1). https://doi.org/10.1038/s42004-025-01478-2

Olefin Oxidation using Organic Framework Catalyst

Metal porphyrin-based covalent organic framework materials (COFs) are synthesized with the objective of transitioning from the use of a multi-step oxidation method for cumene into a single-step process for olefin epoxidation. A carbonyl-ruthenium COF (Ru-COF-1) catalyst was synthesized that showed 98% epoxide selectivity, a high productivity of 1221.77 h⁻¹, while maintaining over 95% selectivity even after nine cycles during the epoxidation of 1-hexene. In depth characterization, structure-performance and mechanistic investigations were performed that indicated that augmented reaction performance results from introduction of Ru metal. This results from improved benzylic proton transfer in cumene and oxygen enrichment from the porous, ordered structure of Ru-COF-1. This enrichment leads to active peroxy radicals with carbon-centered radicals of cumene on the catalyst's surface. Ru-H sites within the catalyst framework speeds the transfer of active oxygen from peroxy radicals, affording tandem epoxidation of olefins. This novel process offers significant improvements over the conventional multi-step industrial oxidation of cumene since it is a safer, more efficient single step approach that uses only air to generate organic peroxides at a safe concentration.

In support of this work, ReactIR measurements were performed in an autoclave reactor to investigate the catalytic process by tracking changes in the functional groups in the epoxidation. The results from these real-time measurements indicated that the epoxidation reaction reached equilibrium simultaneously with the equilibrium of cumene conversion and further validates that cumene functions as an oxygen transfer mediator. Further examination using High Resolution Mass Spectroscopy, Electron Spin Resonance measurements and Density Functional Theory calculations elucidated and validated a proposed mechanism for air oxidant-alkene epoxidation using the Ru-COF-1 catalyst.

Li, D., Xiong, C., Mao, Q., Xi, L., Yang, T., Hu, P., & Ji, H. (2025). Boosting cumene hydrogen transfer via a Ru-based porphyrin covalent organic framework for tandem air epoxidation of olefins. Nano Research. https://doi.org/10.26599/nr.2025.94907892

Organocatalyzed Amidation of Carboxylic Acids and Amines

The authors comment that using a Lewis acid as a catalyst for amidation between carboxylic acids and amines would be an ecofriendly method, and that an appropriate boron compound would likely be effective in this role. Further, they state that using a readily accessible and inexpensive reagent such as bis(pinacolato)diboron (B2pin2) would be attractive as a catalyst for the reaction. They hypothesize that the low catalytic activity of B2pin2 due to the lack of a proton acceptor could be overcome by coordination with the oxygen atom of a carboxylic acid. This coordination would be challenging due to the low acidity of the boron atom, however, introducing electron donating substituents such as an N-Heterocyclic carbene (NHC) onto the boron atom could overcome this issue. Thus, they suggest that an NHC-diboron adduct would form, enabling the boron atom to coordinate with the carboxyl oxygen atom of the carboxylic acid. This, in turn, would generate an active species of NHC diboron-carboxylic acid to catalyze the amidation of carboxylic acids and amines.

Mechanistic investigations were performed to explore this hypothesis. DFT calculations provided theoretical support for the feasibility of constructing the amide bond between carboxylic acids and amines via the active species of NHC diboron-carboxylic acid. In-situ FTIR experiments using ReactIR showed the formation of the N-heterocyclic carbene (NHC)-diboron adduct intermediate. When benzoic acid was introduced, the in-situ FTIR measurements showed coordination of that adduct with the carboxylic acid, leading to the formation of the true active species, NHC-diboron-carboxylic acid, for catalyzing the amidation.

The authors report that this synthesis strategy enabled functionalization of three drug molecules or pharmaceutical intermediates, as well as dipeptide synthesis from a range of amines with protected amino groups.

Wu, D., Wang, Y., Tao, S., Wang, T., Chen, F., Du, Z., Bo, C., Li, M., Dai, B., Wei, D., & Liu, N. (2025). N‐Heterocyclic Carbene‐Diboron‐Substrate cooperatively facilitate direct amidation of carboxylic acids and amines. Advanced Synthesis & Catalysis. https://doi.org/10.1002/adsc.202401441

Technology Referenced in This Article

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This story was part of the METTLER TOLEDO AutoChem #MTCiting series. In this series we dive into the latest published research on innovative applications in research & development.

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