Designing efficient and facile recoverable catalysts is desired for sustainable biomass valorization. This work reports the one-pot synthesis of a novel magnetic Fe­(NiFe)­O4–SiO2 nanocatalyst for hydrogenation of biomass-derived furfural into valuable furfuryl alcohol. Various techniques were used to systematically analyze the physicochemical properties of the Fe­(NiFe)­O4–SiO2 nanocatalyst. Vibrating sample magnetometer analysis reveals low coercivity of Fe­(NiFe)­O4–SiO2 (6.991 G) compared with that of Fe3O4–SiO2 (27.323 G), which is attributed to highly dispersed Ni species in the Fe­(NiFe)­O4–SiO2 catalyst. HRTEM images indicated the nanosized nature of the Fe­(NiFe)­O4–SiO2 catalyst with an average diameter of ∼14.32 nm. The Fe­(NiFe)­O4–SiO2 catalyst showed a superior BET surface area (259 m2/g), which is due to the formation of nanosized particles. The magnetic Fe­(NiFe)­O4–SiO2 nanocatalyst shows a remarkable performance with 94.3 and 93.5% conversions of furfural and ∼100% selectivity of furfuryl alcohol at 90 °C and 20 H2 bar and 250 °C and 5 H2 bar, respectively. Using heptane as a solvent, the effect of temperature, pressure, reactant amount, and catalyst loading were investigated to optimize the reaction conditions. A probable mechanism via a non-hydrogen spillover route was proposed for the hydrogenation of furfural to furfuryl alcohol over the magnetic Fe­(NiFe)­O4–SiO2 nanocatalyst. The efficiency of the magnetic Fe­(NiFe)­O4–SiO2 nanocatalyst is attributed to highly dispersed nickel species, which plays a key role in the dissociation of H2 into a proton and a hydride in the furfural hydrogenation. The superior performance of the magnetic Fe­(NiFe)­O4–SiO2 nanocatalyst, along with the advantages of low cost and easy recoverability, could make it a new appealing catalyst in various selective hydrogenation reactions.

Deep eutectic solvents (DESs) are efficient media for CO 2 capture, and an electroreduction process using the deterministic surface of single-atom electrocatalysts is a facile way to screen gas absorption capacities of novel DESs. Using newly prepared transition-metal-based DESs indexed as TDESs, the interfacial mechanism, detection, quantification, and coordination modes of CO 2 were determined for the first time. The CO 2 has a minimum detection time of 300 s, whereas 500 s of continous ambient CO 2 saturation provided ZnCl 2 /ethanolamine (EA) (1:4) and CoCl 2 /EA (1:4) TDESs with a maximum CO 2 absorption capacity of 0.2259 and 0.1440 mmol/L, respectively. The results indicated that CO 2 coordination modes of η 1 (C) and η 2 (O, O) with Zn in ZnCl 2 /EA (1:4) TDESs are conceivable. We found that the transition metals in TDESs form an interface at the compact layer of the electrocatalyst, while CO 2 •– /CO 2 reside in the diffuse layer. These findings are important because they provide reliable inferences about interfacial phenomena for facile screening of CO 2 capture capacity of DESs or other green solvents.

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Climate engineering solutions with emphasis on CO2 removal remain a global open challenge to balancing atmospheric CO2 equilibrium levels. As a result, warnings of impending climate disasters are growing every day in urgency. Beyond ordinary CO2 removal through natural CO2 sinks such as oceans and forest vegetation, direct CO2 conversion into valuable intermediaries is necessary. Here, a direct electrosynthesis of the peroxydicarbonate anion (C2O6 2–) was investigated by the reaction of CO2 with the superoxide ion (O2 · –), electrochemically generated from O2 reduction in bis­(trifluoromethylsulfonyl)­imide [TFSI–] anion derived ionic liquid (IL) media. This is the first time that the IL media were employed successfully for CO2 conversion into C2O6 2–. Moreover, the charge transfer coefficient for the O2 · – generation process in the ILs was less than 0.5, indicating that the process was irreversible. Voltammetry experiments coupled with global electrophilicity index analysis revealed that, when CO2/O2 was contacted simultaneously in the IL medium, O2 · – was generated in situ first at a potential of approximately −1.0 V. Also, CO2 was more susceptible to attack by O2 · – before any possible interaction with the IL except for [PMIm+]­[TFSI–]. This was because CO2 has a higher global electrophilicity index (ωCO2 = 0.489 eV) than those for the [EDMPAmm+]­[TFSI–] and [MOEMMor+]­[TFSI–]. By further COSMO-RS modeling, CO2 absorption was proven feasible at the COSMO-surface of the [TFSI–] IL-anion where the charge densities were σ = −1.100 and 1.1097 e/nm2. Therefore, the susceptible competitiveness of either IL cations or CO2 to the nucleophilic effects of O2 · – was a function of their positive character as estimated by their electrophilicity indices. As determined by experimental attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and DFT-FTIR computation, the reaction yielded C2O6 2– in the ILs. Consequently, the presence of O=O symmetric stretching FTIR vibrational mode at ∼844 cm–1 coupled with the disappearance of the oxidative cyclic voltammetry waves when sparging CO2 and O2 confirmed the presence of C2O6 2–. Moreover, based on DFT/B3LYP/6-31G, pure C2O6 2– has symmetric O=O stretching at ∼805 and ∼844 cm–1 when it is in association with the IL-cation. This was the first spectroscopic observation of C2O6 2– in ILs, and the O=O symmetric stretching vibration has peculiarity for identifying C2O6 2– in ILs. This will open new doors to utilize CO2 in industrial applications with the aid of reactive oxygen species.