Polymeric Ruthenium Porphyrin-Functionalized Carbon Nanotubes and Graphene for Levulinic Ester Transformations into γ-Valerolactone and Pyrrolidone Derivatives

Abstract

Polymeric ruthenium porphyrin-functionalized carbon nanotubes (Ru-PP/CNTs) were prepared by the metallation of polymeric porphyrin-functionalized carbon nanotubes (PP/CNTs) with Ru 3 (CO) 12 , whereas PP/CNTs were obtained by the condensation of terephthaldehyde and pyrrole in the presence of CNTs. The Ru-PP/CNTs have a thin layer of highly cross-linked polymeric ruthenium porphyrin coating over the CNT surface via strong π–π stacking interactions, thus showing a bilayered structure with an amorphous polymeric outer surface and an internal CNT core. Polymeric ruthenium porphyrin-functionalized reduced graphene oxide (Ru-PP/RGO) was prepared with a synthetic procedure similar to Ru-PP/CNTs, with RGO as the internal core. Both Ru-PP/CNTs and Ru-PP/RGO showed excellent catalytic performance toward hydrogenation of biomass-related ethyl levulinate (EL) to γ-valerolactone (GVL) with Ru-centered porphyrin units as the catalytic active species. Under optimized reaction conditions, a GVL yield higher than 99% with a complete conversion of EL was observed over both Ru-PP/CNTs and Ru-PP/RGO. In addition to GVL preparation, the versatile Ru-PP/CNTs can efficiently promote reductive amination of EL with various amines for the synthesis of pyrrolidone derivatives, with the corresponding yields ranging from 96.3 to 88.7%. Moreover, the composite materials of both Ru-PP/CNTs and Ru-PP/RGO behave as heterogeneous catalysts in the reaction system and can be easily reused.

Iridium Tetra(4‐carboxyphenyl) Porphyrin, Calix[4]pyrrole and Tetraphenyl Porphyrin Complexes as Potential Hydrogenation Catalysts

“…Similarly SBA‐AM‐IrTPP shows peaks at 60.09 eV and 64.24 eV characteristic of iridium in trivalent oxidation state. The signal observed at 399 eV in the N 1S XPS spectra is characteristic of N‐ligand present in the complexes coordinated with Ir 3+ , confirming the existence of Ir (III) centred TCPP, CP, TPP units in SBA‐AM‐IrTCPP, SBA‐AM‐IrCP, SBA‐AM‐IrTPP respectively (Figure ). Further the XPS spectra of C 1s, Cl 2p also supports the existence of IrTCPP, IrCP, IrTPP in the heterogeneous grafted samples (See ESI* Figure S4, S5).…”

“…To understand the nature of the active species, present on the surface, XPS has been carried out, and the Ir 4f core level spectra of SBA‐AM‐IrTCPP, SBA‐AM‐IrCP and SBA‐AM‐IrTPP samples are shown in Figure . The XPS spectrum of both the IrTCPP and IrCP grafted samples show two prominent peaks due to spin‐orbital splitting of Ir 4f 7/2 and Ir 4f 5/2 with binding energies at 61.33 eV and 64.30 eV indicating that iridium is exclusively present with Ir (III) oxidation state on the surface and might act as the centre of hydrogenation reaction . Similarly SBA‐AM‐IrTPP shows peaks at 60.09 eV and 64.24 eV characteristic of iridium in trivalent oxidation state.…”

“…The development of such iridium complexes may broaden the scope as catalysts and may act as model molecules for biological, photophysical and chemical activities , . In other words, in recent years, great attention has been focused on the conversion of biomass into valuable chemicals, in which group VIII metal complexes play a vital role , , . In particular, hydrogenation of levulinic acid to γ‐valerolactone and 1,4‐pentanediol has a significant role as a green solvent, as well as an important intermediate in several fine chemical syntheses , .…”

Selective Catalytic Transfer Hydrogenolysis of Glycerol to 2-Isopropoxy-Propan-1-Ol over Noble Metal Ion-Exchanged Mordenite Zeolite

“…XPS analysis was performed to determine the chemical and electronic state of Ru, Pd, and Rh species in the MOR zeolite samples. Figure 3a shows the full scan survey spectra of RuMOR(cal), PdMOR(cal), and RhMOR(cal), confirming the existence of Ru, Pd, and Rh in the respective RuMOR (~280.0−286.0 eV), PdMOR (~334.0−345.0 eV), and RhMOR (~307.0−31.05 eV) catalysts [21]. Figure 3b−m present the deconvoluted and fitted Ru3d, Pd3d, and Rh3d XPS spectra, along with the O1s, Si2p, and Al2p XPS spectra.…”

Sustainable Catalytic Synthesis for a Bio‐Based Alternative to the Reach‐Restricted N‐Methyl‐2‐Pyrrolidone

“…Besides inorganic metal oxides, organic materials were also exploited as support. Ru onto porphiryn‐functionalized carbon nanotubes showed to be effective, nevertheless under harsh conditions,31 whereas Ru@N‐heterocyclic carbene polymer gave 5MPs using ammonium formate, serving both as hydrogen transfer agent and nitrogen source 32. Use of formic acid as imine reducing agent was advantageous in some occasions, e.g., gold nanoparticles onto acid‐tolerant ZrO 2 ,33 taking advantage of the equimolar mixtures of formic and levulinic acid obtained by acidic hydrolysis of biomass 25a,b.…”