Novel and selective strategies for platform chemical production from renewable biomass are highly attractive in respect to value-added utilization of sustainable resources. In this study, a series of low-cost, commercially available, transition metal carbonates (Zr, Ni, Mg, Zn, and Pb) were investigated for catalytic transfer hydrogenation of levulinate esters to γ-valerolactone (GVL) via the cascade process of Meerwein−Ponndorf−-Verley (MPV) reduction and lactonization reaction. Among the selected catalysts, basic zirconium carbonate is the most active, with the highest turnover frequency (TOF) of 3.1 h −1 and a surface reaction rate of 0.21 mol m −2 h −1 . At 453 K, 3.0 h, and 1.0 MPa N 2 , 100% ethyl levulinate conversion, 96.3% GVL yield, and 91.9% hydrogen donor utilization are observed due to the cooperative effect between acid (M n+ ) and base (−OH) sites. Furthermore, this catalyst shows high recyclability under the optimized conditions, where a satisfactory catalytic activity is shown even after six consecutive runs.

Heterogeneous single-metal-site catalysts have been drawing increasing interests in the field of academy and industry because of the comparable catalytic activity with homogeneous catalyst and easy separation.Here, an efficiently heterogeneous single-site Rh catalyst on activated carbon (Rh 1 /AC) was constructed, which performs three times activity than the corresponding homogeneous catalyst for methanol carbonylation. Experimental data reveals that the apparent activation energy on the Rh 1 /AC catalyst is 0.91 eV, far less than 1.54 eV of its homogeneous counterpart. Ex situ EXAFS confirms the molecular configuration of a single Rh site. DFT calculation demonstrates that the electron-donating carbonyl group on the surface of the support possesses the precedence to accommodate the singlesite Rh ions. Furthermore, difference charge density verifies that the coordinative bond between a single metal ion and a carbonyl group enhances the electronic density of the central Rh atom, consequently lowering the energy barrier of the rate-determining step of CH 3 I oxidative addition. Together with the atomic dispersion, as well as the electronic interaction between a single Rh ion and carbonyl groups, the Rh 1 /AC catalyst performs superior activity than homogeneous systems.

Heterogeneous single-metal-site catalysts (HSMSCs) have attracted considerable interest, but most studies have focused on the metal atoms in the active site while ignoring the key role of ligands. The unique coordination environment of a single-site catalyst is crucial for realizing its potential. Constructing this kind of catalyst via a feasible and practical fabrication method is challenging. Herein, a single-site Pd catalyst with iodide ligands supported on activated carbon (Pd1/AC) was successfully fabricated by atomic dispersion of large Pd nanoparticles (NPs). Intermediate I• radicals were detected during the atomic dispersion process of Pd NPs by in situ imaging photoelectron photoion coincidence spectroscopy (in situ iPEPICO) with vacuum ultraviolet synchrotron radiation. The molecular structure of single-site Pd was established as [Pd­(CO)­I4(OAC)]2– through combined characterization. Alkyne dialkoxycarbonylation with high selectivity toward 1,4-dicarboxylic acid esters (>94%) and high acetylene conversion (>99%) was achieved. A sulfonic promoter on the Pd1/AC catalyst for alkyne dialkoxycarbonylation was avoided because of the iodide ligand. Good durability and a broad substrate scope were successfully achieved.