Single atom In-MXene as viable catalyst for the cinnamaldehyde transformation

Title : Single atom In-MXene as viable catalyst for the cinnamaldehyde transformation

Abstract:

Cinnamyl alcohol (COL) is an important intermediate in both the pharmaceutical and perfumery industries [1] and, as consequence, merely produced through the chemical synthesis under heterogeneous catalysts [2] with molecular hydrogen in a liquid medium under controlled pressure and at acceptable temperature conditions [3]. To reach this objective, several solid catalysts as mixed oxides [4], metal, bimetal and supported nanoparticles catalysts [5] were considered as alternatives.

To improve the behavior of such catalysts this study recommended a new class of solids, ie the MXenes corresponding to 2D materials where M is an early single transition metal (e.g. Ti, V, Hf, Nb, Zr), X is nitrogen or carbon, while T is a surface functional group (e.g. O, F, OH) with tunable polarized active sites generating an increased catalytic activity.

Thus, starting from this state of the art, this research proposed a new approach focusing the synthesis of single atom MXenes through association of indium with Ti ((In,Ti)C or In-Ti₃C₂Cl₂) for the hydrogenation/oxidation of the double bonds of cinnamaldehyde in the presence of molecular hydrogen or oxygen.

The catalysts were exhaustively characterized by XRD (Figure 1), Raman, DRIFT and XPS analysis, H₂, CO₂ -TPD, In terms of the conversion, the catalytic activity in the hydrogenation of cinnamaldehyde varied as a function of the catalyst 36.35% for In-Ti₃C₂Cl₂,. The absence of the hydrogen as a reactant did not represent an obstacle to carry out this catalytic reaction because it can be supplied by the solvent (ie the iso-propyl alcohol through the disproportionation).

Single atom MXenes demonstrated a viable catalyst behavior for both the cinnamaldehyde selective hydrogenation and the selective oxidation. The behavior of these MXenes has been evaluated in comparison with that of In₂O₃ as reference. For the cinnamaldehyde the hydrogenation occurred with high TONs and TOFs ie In-Ti₃C₂Cl₂ (TON 391.63 and TOF 78.33 h^-1) and In₂O₃ (TON 988.78 and TOF 197.76 h^-1) as well.  Then, on few MXenes, these catalysts the provided pretty high selectivity to cinnamyl alcohol, ie 85.03% on In-Ti₃C₂Cl₂, and 60.58% on (In,Ti)C, compared to only 9.87% on In₂O₃, that is justified by the composition. Noteworthy, these catalysts also demonstrated a robust stability.

In conclusion, the MXenes with indium shown still a good activity for the investigated reactions. However, the disposal of indium in the MXene matrices limited the catalytic activity of these materials.

Biography:

Prof. Vasile Parvulescu is professor emeritus at the University of Bucharest and Corresponding member at the Romanian Academy. His research focuses the development of catalysts for the synthesis of fine chemicals, production of energy, valorization of biomass and the protection of the environment.  To achieve this, structure-activity-selectivity relationships are established for the different types of heterogeneous catalysts (supported metal nano-particles, zeolites and molecular sieves, carbon-based materials, MOF, organic functionalized inorganic catalysts) using both in-situ and ex-situ techniques (XRD, FTIR, UV-Vis, Raman, XPS, etc).