Ni Center Research Articles

Cyclic voltammetry electrodeposition of self-standing Ni–Fe–Sn ternary alloys for accelerating alkaline hydrogen evolution

Designing cost-effective and high-efficiency non-noble electrocatalysts for the hydrogen evolution reaction (HER) remains a significant challenge for electrochemical water splitting to store clean and renewable energy. Herein, we have developed Ni–Fe–Sn electrocatalysts grown on Ni foam (Ni–Fe–Sn@NF) for the HER through a simple and facile synthetic route of cyclic voltammetry electrodeposition. The optimized Ni–Fe–Sn electrocatalysts possess excellent electrocatalysis toward hydrogen evolution with a low overpotential of 103 mV at a current density of 10 mA cm−2, together with a small Tafel slope value of 97.4 mV·dec−1 in 1 M KOH. The electrocatalyst also features excellent stability even after 2000 cycles and strong durability after 50 h under alkaline condition. The high HER performance can be attributed to the moderately optimized electronic structure of the Ni, Fe, and Sn center and bind-free nature of the electrode, which facilitates electron transfer and speeds up reaction kinetics. Moreover, the improved electrochemical surface area also enhances the performance on hydrogen production. This strategy presents a facile and simple tactic for the synthesis of noble-metal-free electrocatalysts with excellent HER performance.

B12 and F430 models: Metal- versus ligand-centered redox in cobalt and nickel tetradehydrocorrin derivatives

DFT calculations with the well-tested OLYP and B3LYP* exchange-correlation functionals (along with D3 dispersion corrections and all-electron ZORA STO-TZ2P basis sets) and careful use of group theory have led to significant insights into the question of metal- versus ligand-centered redox in Co and Ni B,C-tetradehydrocorrin complexes. For the cationic complexes, both metals occur in their low-spin M(II) forms. In contrast, the charge-neutral states vary for the two metals: while the Co(I) and CoII-TDC•2– state are comparable in energy for cobalt, a low-spin NiII-TDC•2– state is clearly preferred for nickel. The latter behavior stands in sharp contrast to other corrinoids that reportedly stabilize a Ni(I) center.

A New 1D Ni (II) Coordination Polymer of s-Triazine Type Ligand and Thiocyanate as Linker via Unexpected Hydrolysis of 2,4-Bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine

A new 1D Ni(II) coordination polymer was synthesized by the reaction of NiSO4·6H2O with 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine (BPT) and SCN− as a linker in an acidic medium by heating under reflux conditions. Unusually, the BPT ligand underwent acid-mediated hydrolysis by losing one of the pyrazolyl arms afforded the polymeric [Ni(MPT)(H2O)(SCN)2]n complex (MPT: 4-(3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazin-2-ol. The Ni(II) center is coordinated with one MPT as a bidentate NN-chelate, one water molecule, and two thiocyanate groups in cis positions to one another. One of the thiocyanate groups acts as a bridging ligand between metal centers, leading to a one-dimensional polymeric structure that extends along the c-direction. The other thiocyanate group is terminally N-coordinated. The [Ni(MPT)(H2O)(SCN)2]n complex has been screened in vitro against two pathogenic fungal strains: A. fumigatus, C. albican, and four pathogenic bacterial strains: S. aureus, B. subtilis as gram-positive bacteria, E. coli, P. vulgaris as gram-negative bacteria. The results showed that the complex has the potential to be used as both an antibacterial and an antifungal agent. Also, the [Ni(MPT)(H2O)(SCN)2]n complex showed cytotoxic activities against hepatocellular (HepG-2) and lung (A-549) cell lines, with IC50 values of 132.67 ± 5.14 and 146.97 ± 7.34 μM, respectively.

Theoretical Assessment of the Mechanism and Active Sites in Alkene Dimerization on Ni Monomers Grafted onto Aluminosilicates: (Ni-OH)+ Centers and C-C Coupling Mediated by Lewis Acid-Base Pairs.

Ni-based solids are effective catalysts for alkene dimerization, but the nature of active centers and identity and kinetic relevance of bound species and elementary reactions remain speculative and based on organometallic chemistry. Ni centers grafted onto ordered MCM-41 mesopores lead to well-defined monomers that are rendered stable by the presence of an intrapore nonpolar liquid, thus enabling accurate experimental inquiries and indirect evidence for grafted (Ni-OH)+ monomers. Density functional theory (DFT) treatments presented here confirm the plausible involvement of pathways and active centers not previously considered as mediators of high turnover rates for C2-C4 alkenes at cryogenic temperatures. (Ni-OH)+ species act as Lewis acid-base pairs that stabilize C-C coupling transition states by polarizing two alkenes in opposite directions via concerted interactions with the O and H atoms in these pairs. DFT-derived activation barriers for ethene dimerization (59 kJ mol-1) are similar to measured values (46 ± 5 kJ mol-1) and the weak binding of ethene on (Ni-OH)+ is consistent with kinetic trends that require sites to remain essentially bare at subambient temperatures and high alkene pressures (1-15 bar). DFT treatments of classical metallacycle and Cossee-Arlman dimerization routes (Ni+ and Ni2+-H grafted onto Al-MCM-41, respectively) show that such sites bind ethene strongly and lead to saturation coverages, in contradiction with observed kinetic trends. These C-C coupling routes at acid-base pairs in (Ni-OH)+ differ from molecular catalysts in (i) the type of elementary steps; (ii) the nature of active centers; and (iii) their catalytic competence at subambient temperatures without requiring co-catalysts or activators.

Sulfido-bridged 1,2-bis(diphenylphosphino)ethane (dppe) appended trinuclear nickel(II) clusters: Crystallographic and computational analyses

The cluster compounds are still gaining considerable attention due to their peculiar behaviour and M−M bonding or M···M interactions. In this report, two sufido-bridged, 1,2-bis-(diphenylphosphino)ethane (dppe) appended trinuclear Ni(II) clusters having formula [Ni3S2(dppe)3].2BPh4 (Ni3S2-1) and [Ni3S2(dppe)2(4-pyCH2OH)2].2PF6 (Ni3S2-2) are reported. These clusters are synthesized from the same starting reactants the xanthate ligand 4-PyCH2OCS2Na, Ni(II) and dppe employing two different reaction pathways. The obtained compounds have been characterized by microanalyses, FTIR, UV–Vis, 1H, 13C and 31P NMR spectroscopy as well as by single crystal X-ray diffraction technique. The X-ray analyses revealed that in both compounds three Ni(II) centers are coordinated to two sulfido and dppe ligands. In Ni3S2-1 three dppe and two sulfido ligands are stabilising the trinuclar cluster cation while in Ni3S2-2 along with two sulfido and two dppe ligands, two 4-pyCH2OH are also coordinating with one of the Ni(II) center. Both Ni3S2-1 and Ni3S2-2 display different non-covalent interactions along with the Ni···Ni interactions. The nature of these interactions has been addressed with the aid of Hirshfeld surface analysis, density functional theory and quantum theory of atoms-in-molecules (QTAIM) analyses. The occurrence of such non-covalent intermolecular interactions is also well supported by the non-covalent interactions reduced density gradient (NCI-RDG) approaches. Also, the Wiberg bond index, Mayer bond order and delocalization indices have been calculated to assess the nature of Ni···Ni interactions.

Modulating morphology and textural properties of Al2O3 for supported Ni catalysts toward plasma-assisted dry reforming of methane

The synergy between plasma and catalysis has been long noticed, but how to further improve the synergy remains challenging. Herein, a series of Ni/Al2O3 catalysts with different Al2O3 morphologies (nanorod-NR, nanosheet-NS and spherical flower-SF) were investigated for plasma-assisted dry reforming of methane (DRM). Surface properties, metal dispersion, and discharge properties were modulated, and thereby affected catalytic performance and plasma-catalysis synergistic efficiency. Sufficient surface hydroxyls on NS-Al2O3 dispersed and anchored Ni centers via forming Ni-O-Al linkages, and the specific two–dimensional structure facilitated charge deposition and generated a stronger local electric field. Accordingly, the Ni/NS-Al2O3 catalyst showed the best catalytic activity & stability and energy efficiency in the reaction. The present study provides a promising strategy to enhance the synergy and energy efficiency of plasma-catalysis by coupling highly dispersed Ni active centers and specific structures of Al2O3 substrate to obtain an efficient catalyst motivating the DRM reaction under mild conditions.

One-Dimensional π-d Conjugated Coordination Polymer Intercalated MXene Compound for High-Performance Supercapacitor Electrode.

MXenes possess the characteristics required for high-performance supercapacitors, such as high metallic conductivity and electrochemical activity, but their full potential remains unrealized owing to their tendency to self-restack when fabricated into an electrode. Designing an MXene interlayer with an effective intercalant has, therefore, become an important criterion to alleviate the restacking issue while also synergistically interact with MXene to further improve its electrochemical activity. This study reports the intercalation of 1D π-d conjugated coordination polymer (Ni-BTA) within the Ti3 C2 Tx nanosheet for the fabrication of a highly efficient supercapacitor electrode. Ni-BTA, which consists of a nickel center and 1,2,4,5-benzenetetramine (BTA) organic chain, is uniformly intercalated by direct synthesis on the abundant oxygen terminals on the Ti3 C2 Tx nanosheet surface. The intercalated Ni-BTA acts as an effective charge carrier transportation pathway through its 1D stretched delocalized π-d electrons while participating in pseudocapacitive activity with the Ni centers. As a result, the Ni-BTA/MXene film exhibits excellent rate performance and a gravimetric specific capacitance of 264.4Fg-1 at 5mVs-1 . This magnitude is retained up to 94.6% after 10000 cycles. The present study provides insights into the design of MXene interlayers for the fabrication of highly robust and stable supercapacitors.

The strengthening effects and mechanisms of alloying elements on interfaces for multiphase Ni-based superalloys: A first-principles study

The mechanical properties and thermal stability of multiphase Ni-based superalloys are highly determined by the interfaces between the strengthening precipitations and the matrix. In this work, the interface properties of the γ/γ′/γ″ system are investigated using the first-principles calculations, and the strengthening mechanisms of alloying elements (3 d, 4 d and 5 d transition-metals) on the γ/γ″ and γ′/γ″ coexisting interfaces have been evaluated systematically. It was found that the matching configuration of the Ni (Center) + X (termination) is thermodynamically the most stable interface structure. The multi-interfaces doping results demonstrate that W, Re, Mo, Ta, Tc preferably occupy Nb-cp position and Fe, Co, Os tend to substitute Ni-fc position. Among these, W and Re have most significant effect on improving the bonding strength of γ/γ″ and γ′/γ″ interfaces synergistically. The dependence of interfacial cohesion on the metal radius and the concentration of specific elements are discussed as well. The corresponding analysis of electronic structures reveals that the strengthening effect of alloying elements can be ascribed to the increased chemical bonding strength between the doping atom and the nearest-neighbor host atom. The results of this work can shed light on developing novel Ni-based superalloys combinedly strengthened by γ′ and γ″ phases.

Experimental and Computational Investigation of Facial Selectivity Switching in Nickel-Diamine-Acetate-Catalyzed Michael Reactions.

Chiral Ni complexes have revolutionized both asymmetric acid-base and redox catalysis. However, the coordination isomerism of Ni complexes and their open-shell property still often hinder the elucidation of the origin of their observed stereoselectivity. Here, we report our experimental and computational investigations to clarify the mechanism of β-nitrostyrene facial selectivity switching in Ni(II)-diamine-(OAc)2-catalyzed asymmetric Michael reactions. In the reaction with a dimethyl malonate, the Evans transition state (TS), in which the enolate binds in the same plane with the diamine ligand, is identified as the lowest-energy TS to promote C-C bond formation from the Si face in β-nitrostyrene. In contrast, a detailed survey of the multiple potential pathways in the reaction with α-keto esters points to a clear preference for our proposed C-C bond-forming TS, in which the enolate coordinates to the Ni(II) center in apical-equatorial positions relative to the diamine ligand, thereby promoting Re face addition in β-nitrostyrene. The N-H group plays a key orientational role in minimizing steric repulsion.

Modification of Al2O3‐based catalyst by rare earth elements for steam reforming of methane

AbstractModification of rare earth elements (Ln) often contributes to the improved performance in many applications compared with the monometallic catalysts, but the current research is only limited in the individual light rare earth elements. In this work, a series of Ln elements involving Gd, Sm, Nd, Pr, and La was added into monometallic Ni/Al2O3 system to focus how the microstructure of active Ni centers depended on the presence and contents of Ln, and thus improved the catalytic behavior in the steam reforming of methane. Enhanced catalytic behavior could be observed over Ln‐modified Ni catalysts, among which Ni‐Gd/Al2O3 was predicted to be more high‐efficient no matter supported on power or spherical Al2O3 catalysts. A combined investigation of XPS with STEM and TPR was carried out over the candidates to reveal the structure‐performance relationship. Furthermore, this was further applied to noble metal systems, realizing the benign universality of the modification strategy.

Centrosymmetric Nickel(II) Complexes Derived from Bis-(Dithiocarbamato)piperazine with 1,1′-Bis-(Diphenylphosphino)ferrocene and 1,2-Bis-(Diphenylphosphino)ethane as Ancillary Ligands: Syntheses, Crystal Structure and Computational Studies

Two Ni(II) complexes with the formula [{Ni(dppf)}2{(L1)2}](PF6)2 (Ni-I) and [{Ni(dppe)}2{(L1)2}](PF6)2 (Ni-II) were prepared by reacting [Ni(dppf)Cl2] and [Ni(dppe)Cl2] (dppf = 1,1′-Bis-(diphenylphosphino)ferrocene; dppe = 1,2-Bis-(diphenylphosphino)ethane) with secondary amine piperazine derived ligand disodium bis-(dithiocarbamate)piperazine ((piper(dtc)2 = L1) and counter anion PF6−. These complexes were characterized by elemental analyses, FT-IR, 1H, 13C and 31P NMR, UV-Vis. spectroscopy and single crystal X-ray diffraction. The X-ray analyses reveal centrosymmetric structures where each Ni(II) centre adopts distorted square planar geometry defined by two sulfur centres of dithiocarbamate ligand and two phosphorus centres of dppf and dppe ligands in Ni-I and Ni-II, respectively. The supramolecular framework of both Ni-I and Ni-II are sustained by C-H⋯π and C-H⋯F interactions, and they also display interesting intramolecular C-H⋯Ni anagostic interactions. Further, the nature of these interactions are studied using Hirshfeld surface analyses, DFT and quantum theory of atoms in molecules (QTAIM) calculations. Additionally, non-covalent interaction (NCI) plot analyses were conducted to gain additional insight into these non-covalent interactions. This work is vital in a new approach towards the rational designing of the centrosymmetric molecules with interesting architectures.

Tungsten Disulfide-Interfacing Nickel-Porphyrin For Photo-Enhanced Electrocatalytic Water Oxidation.

Covalent functionalization of tungsten disulfide (WS2 ) with photo- and electro-active nickel-porphyrin (NiP) is reported. Exfoliated WS2 interfacing NiP moieties with 1,2-dithiolane linkages is assayed in the oxygen evolution reaction under both dark and illuminated conditions. The hybrid material presented, WS2 -NiP, is fully characterized with complementary spectroscopic, microscopic, and thermal techniques. Standard yet advanced electrochemical techniques, such as linear sweep voltammetry, electrochemical impedance spectroscopy, and calculation of the electrochemically active surface area, are used to delineate the catalytic profile of WS2 -NiP. In-depth study of thin films with transient photocurrent and photovoltage response assays uncovers photo-enhanced electrocatalytic behavior. The observed photo-enhanced electrocatalytic activity of WS2 -NiP is attributed to the presence of Ni centers coordinated and stabilized by the N4 motifs of tetrapyrrole rings at the tethered porphyrin derivative chains, which work as photoreceptors. This pioneering work opens wide routes for water oxidation, further contributing to the development of non-noble metal electrocatalysts.

Enhanced demethylation of aromatic ether to phenol over NiAl hydrotalcite-derived nickel sulfide catalyst

The production of phenol from lignin or its model compounds, instead of cumene oxidation is very interesting from the viewpoint of sustainability and economics. The selective demethylation of anisole was an efficient but challenging route to produce phenol. In this work, we demonstrated the fabrication of nickel sulfide (Ni9S8+NixS6) nanoparticles on Al2O3 matrix by a facile in situ sulfidation of NiAl hydrotalcite and announced that nickel sulfide can serve as efficient active site for the demethylation of anisole for the first time. The as-designed 4Ni1Al-S catalyst exhibited a hierarchical morphology with a high particle density and high dispersion, affording a 95.6% yield of phenol in the demethylation of anisole under relative milder reaction temperature (270 °C) when compared to the reported state-of-the-art results. By comprehensive characterizations and experiments, we inferred that the nickel sulfide exsolved from the LDH structure exhibited stronger metal-support interaction than that obtained from the impregnation method, which not only benefits the uniform dispersion of active nickel sulfide but also results in the electronic transfer from Ni center to Al2O3 support. As a consequence, enhanced demethylation activity was achieved on 4Ni1Al-S in comparison to Ni-S/Al2O3-IM.

Enhanced Energy Transfer in A π‐Conjugated Covalent Organic Framework Facilitates Excited‐State Nickel Catalysis

AbstractCovalent organic frameworks (COFs) have received broad interest owing to their permanent porosity, high stability, and tunable functionalities. COFs with long‐range π‐conjugation and photosensitizing building blocks have been explored for sustainable photocatalysis. Herein, we report the first example of COF‐based energy transfer Ni catalysis. A pyrene‐based COF with sp2 carbon‐conjugation was synthesized and used to coordinate NiII centers through bipyridine moieties. Under light irradiation, enhanced energy transfer in the COF facilitated the excitation of Ni centers to catalyze borylation and trifluoromethylation reactions of aryl halides. The COF showed two orders of magnitude higher efficiency in these reactions than its homogeneous control and could be recovered and reused without significant loss of catalytic activity.

Enhanced Energy Transfer in A π-Conjugated Covalent Organic Framework Facilitates Excited-State Nickel Catalysis.

Covalent organic frameworks (COFs) have received broad interest owing to their permanent porosity, high stability, and tunable functionalities. COFs with long-range π-conjugation and photosensitizing building blocks have been explored for sustainable photocatalysis. Herein, we report the first example of COF-based energy transfer Ni catalysis. A pyrene-based COF with sp2 carbon-conjugation was synthesized and used to coordinate NiII centers through bipyridine moieties. Under light irradiation, enhanced energy transfer in the COF facilitated the excitation of Ni centers to catalyze borylation and trifluoromethylation reactions of aryl halides. The COF showed two orders of magnitude higher efficiency in these reactions than its homogeneous control and could be recovered and reused without significant loss of catalytic activity.

Accelerating Electrochemical Water Oxidation Activity by Tailoring Morphology and Electronic Structure of Nickel Organic Framework Nanoarrays with a Fe Etching Effect

Fe-mediated nickel organic framework nanoarrays (NiFe-MOFs NAs) on carbon cloth were successfully constructed from ultrathin nanosheets via an etching effect. This strategy also combined the dissolution and coordination effect of acidic ligand (2,6-naphthalenedicarboxylic acid, NDC) to a self-sacrificial template of Ni(OH)2 NAs. Benefiting from the strong Fe etching effect, dense and thick brick-like Ni-NDC nanoplates were tailored into loose and ultrathin NiFe-NDC nanosheets with abundant squamous nanostructures, which were still tightly attached to carbon cloth. As a consequence, more coordinatively unsaturated metal sites (CUMSs) that served as active centers were exposed to accelerate oxygen production. Meanwhile, the electronic structure of active Ni centers was modulated by the incorporation of Fe atoms. The charge density redistribution between Ni and Fe ultimately optimized the energy barrier of the adsorption/desorption of oxygenated intermediates, promoting the kinetics for water oxidation.

Revised Mechanism of C(sp3)-C(sp3) Reductive Elimination from Ni(II) with the Assistance of a Z-Type Metalloligand.

Reductive elimination is a key step in Ni-catalyzed cross-couplings. Compared with processes that proceed from Ni(III) or Ni(IV) intermediates, C(sp3)-C(sp3) reductive eliminations from Ni(II) centers are challenging due to the weak oxidizing ability of Ni(II) species. In this report, we present computational evidence that supports a mechanism in which Zn coordination to the nickel center as a Z-type ligand accelerates reductive elimination. This Zn-assisted pathway is found to be lower in energy compared with direct reductive elimination from a σ-coordinated Ni(II) intermediate, providing new insights into the mechanism of Ni-catalyzed cross-coupling with organozinc nucleophiles. Mayer bond order, Hirshfield charge, Laplacian of the electron density, orbital, and interaction region indicator analyses were conducted to elucidate details of the reductive elimination process and characterize the key intermediates. Theoretical calculations indicate a significant Z-type Ni-Zn interaction that reduces the electron density around the Ni center and accelerates reductive elimination. This mechanistic study of reductive elimination in Ni(0)-catalyzed conjunctive cross-couplings of aryl iodides, organozinc reagents, and alkenes is an important case study of the involvement of Zn-assisted reductive elimination in Ni catalysis. We anticipate that the novel Zn-assisted reductive elimination mode may extend to other cross-coupling processes and explain the unique effectiveness of organozinc nucleophiles in many instances.

Aligning Metal Coordination Sites in Metal–Organic Framework-Enabled Metallaphotoredox Catalysis

Construction of catalytic metal centers, the key modules in artificial photosynthetic systems, lies at the heart to explore unpaved reactivity patterns powered by light. Here, we disclose that the amino (-NH2) and carboxylic (-COO) functionalities, aligned in various visible-light-harvesting metal-organic frameworks (MOFs) (NH2-UiO-66, (NH2)2-UiO-67, and NH2-MIL-125), provide N/O-ligated Ni featuring different configurations and valence states. Of note, these Ni centers, in situ formed or preimplanted, demonstrated coordination units' spatial arrangement-dependent activity in cross-coupling of aryl halides and various nucleophiles. Our work provides a novel approach to construct and to regulate metal center(s) by MOFs' skeleton defined coordination environments, highlighting exclusive potential in exploring the reactivity pattern of the hosted metals.

Theoretical Insight on the High Reactivity of Reductive Elimination of NiIII Based on Energy- and Electron-Transfer Mechanisms.

Iridium/nickel (Ir/Ni) metallaphotoredox dual catalysis overcomes the challenging reductive elimination (RE) of Ni(II) species and has made a breakthrough progress to construct a wide range of C-X (X = C, N, S, and P) bonds. However, the corresponding reaction mechanisms are still ambiguous and controversial because the systematic research on the nature of this synergistic catalysis is not sufficient. Herein, IrIII/NiII and IrIII/Ni0 metallaphotoredox catalysis have been theoretically explored taking the aryl esterification reaction of benzoic acid and aryl bromide as an example by a combination of density functional theory (DFT), molecular dynamics, and time-dependent DFT computations. It is found that an electron-transfer mechanism is applicable to IrIII/NiII metallaphotoredox catalysis, but an energy-transfer mechanism is applicable to IrIII/Ni0 combination. The IrIII/NiII metallaphotoredox catalysis succeeds to construct a NiI-NiIII catalytic cycle to avoid the challenging RE of Ni(II) species, while the RE occurs from triplet excited-state Ni(II) species in the IrIII/Ni0 metallaphotoredox catalysis. In addition, the lower lowest unoccupied molecular orbital energy level of Ni(III) species than that of Ni(II) species accelerates RE from Ni(III) one. The triplet excited-state Ni(II) species can resemble a Ni(III) center, considering the metal-to-ligand charge transfer character to promote the RE.

The Transfer Hydrogenation of Cinnamaldehyde Using Homogeneous Cobalt(II) and Nickel(II) (E)-1-(Pyridin-2-yl)-N-(3-(triethoxysilyl)propyl)methanimine and the Complexes Anchored on Fe3O4 Support as Pre-Catalysts: An Experimental and In Silico Approach

The imino pyridine Schiff base cobalt(II) and nickel(II) complexes (C1 and C2) and their functionalised γ-Fe3O4 counterparts (Fe3O4@C1 and Fe3O4@C2) were synthesised and characterised using IR, elemental analysis, and ESI-MS for C1 and C2, and single crystal X-ray diffraction for C1, while the functionalised materials Fe3O4@C1 and Fe3O4@C2 were characterized using IR, XRD, SEM, TEM, EDS, ICP-OES, XPS and TGA. Complexes C1, C2 and the functionalised materials Fe3O4@C1 and Fe3O4@C2 were tested as catalysts for the selective transfer hydrogenation of cinnamaldehyde and all four pre-catalysts showed excellent catalytic activity. Complexes C1 and C2 acted as homogeneous catalysts with high selectivity towards the formation of hydrocinnamaldehyde (88.7% and 92.6%, respectively) while Fe3O4@C1 and Fe3O4@C2 acted as heterogeneous catalysts with high selectivity towards cinnamyl alcohol (89.7% and 87.7%, respectively). Through in silico studies of the adsorption energies, we were able to account for the different products formed using the homogeneous and the heterogeneous catalysts which we attribute to the preferred interaction of the C=C moiety in the substrate with the Ni centre in C2 (-0.79 eV) rather than the C=O (-0.58 eV).