Nickel(II) complexes have been synthesized and characterized using nuclear magnetic resonance (NMR), infrared spectroscopy, high resolution mass spectroscopy, and elemental analysis. The complexes were evaluated as pre-catalysts in the direct hydrogenation of furfural to furfuryl alcohol. The pre-catalysts C1 and C4 gave higher furfural conversion (97% and 96%, respectively), as a result, they were also evaluated in the transfer hydrogenation of furfural using formic acid as the hydrogen source where higher furfural conversion (93%) was obtained and selectivity (100%) toward the formation of furfuryl alcohol at 4 h. The catalyst C1 was recycled three times with and it was observed that the catalytic activity might be due to a mixture of both molecular catalysis and nanoparticles, as evidenced by the decrease in activity in mercury poisoning experiments. The hydrogenation reactions were also extended to alpha-β unsaturated substrates and were selective toward saturation of the carbonyl functionality over alkene groups.

The use of living plants to recover precious metals with potential catalytic activity is still at the infant stage. In this study, selective hydrogenation of furfural to furfuryl alcohol using novel bio-ore catalysts recovered from the end stage of phytomining process is demonstrated. The phytomining process was carried out in the green house by artificially contaminating cassava (Manihot esculenta) plant with 500 mg/L palladium (Pd) and platinum (Pt) solutions for a period of eight weeks. After harvesting, concentrations of metals as high as 78 ± 0.047 and 1276 ± 0.036 µg/g of Pd and Pt, respectively, were detected in the calcinated root of cassava. The produced bio-ore catalysts; @PdCassCat and @PtCassCat were fully characterized with the following techniques: transmission electron microscopy (TEM), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), powder X-ray diffraction (pXRD), N₂-sorption, and UV-visible spectroscopy techniques and directly applied as catalysts for hydrogenation of furfural to furfuryl alcohol. The reaction was conducted under an optimized condition (furfural (10 mmol), triethylamine (Et₃N) (10 mmol), formic acid (20 mmol), temperature (160 °C), catalyst amount (40 mg)) realizing a yield of 76.5% and 100% furfuryl alcohol using @PdCassCat and @PtCassCat, respectively. The catalytic activities of the @PdCassCat and @PtCassCat were excellent as well as recyclable up to four and five times, respectively.

Novel palladium, rhodium, iron, ruthenium and nickel half‐sandwich picolinamide complexes have been prepared and characterised in detail using high‐resolution electrospray ionisation mass spectrometry (HR‐ESI‐MS), multi‐dimensional nuclear magnetic resonance spectroscopy, elemental analysis (EA), Fourier transform‐infrared spectroscopy (FT‐IR), and single crystal X‐ray diffraction (SCXRD). All the systems proved to be active with good catalytic performance for the hydrogenation of furfural. Among the pre‐catalyst, C2 (Rh metal centre) displayed complete conversion (100%). Pre‐catalyst C5 (Ru metal centre) also resulted in excellent selectivity to EL (51%) and FA (49%). All the pre‐catalysts with early transition metal centres (Ni, Fe) gave selectivity towards FA (100%) under optimal conditions. Possible pathways for the formation of catalytically active have been proposed based on in situ NMR studies obtained using C2. Successful modification of molecular complexes (C2 and C3) on SBA‐15 resulted in supported molecular complexes (C2@SBA‐15 and C3@SBA‐15). Furthermore, the supported molecular catalysts were characterised using inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), Fourier‐transform infrared spectroscopy (FT‐IR), powder X‐ray diffraction (PXRD), BET surface area, selected area electron diffraction (SAED), X‐ray photoelectron spectroscopy (XPS) and high‐resolution transmission electron microscopy (HR‐TEM). The supported molecular complex C2@SBA‐15 was recycled five times (with consistent activity and selectivity).