Metal-organic-framework derived Co-Pd bond is preferred over Fe-Pd for reductive upgrading of furfural to tetrahydrofurfuryl alcohol

Article abstract of DOI:10.1039/c9dt01190k

Combined noble-transition metal catalysts have been used to produce a wide range of important non-petroleum-based chemicals from biomass-derived furfural (as a platform molecule) and have garnered colossal research interest due to the urgent demand for sustainable and clean fuels. Herein, we report the palladium-modified metal-organic-framework (MOF) assisted preparation of PdCo₃O₄ and PdFe₃O₄ nanoparticles encapsulated in a graphitic N-doped carbon (NC) matrix via facile in situ thermolysis. This provides a change in selectivity with superior catalytic activity for the reductive upgrading of biomass-derived furfural (FA). Under the optimized reaction conditions, the newly designed PdCo₃O₄@NC catalyst exhibited highly efficient catalytic performance in the hydrogenation of furfural, providing 100% furfural conversion with 95% yield of tetrahydrofurfuryl alcohol (THFAL). In contrast, the as-synthesized Pd-Fe₃O₄@NC afforded a THFAL yield of 70% after an 8 h reaction with four consecutive recycling tests. Based on different characterization data (XPS, H₂-TPR) for nanohybrids, we can conclude that the presence of PdCo-N_x active sites, and the multiple synergistic effects between Co₃O₄ and Pd(ii), Co₃O₄ and Pd⁰, as well as the presence of N in the carbonaceous matrix, are responsible for the superior catalytic activity and improved catalyst stability. Our strategy provides a facile design and synthesis process for a noble-transition metal alloy as a superior biomass refining, robust catalyst via noble metal modified MOFs as precursors.

Full text of DOI:10.1039/c9dt01190k

View Article Online
View Journal
Dalton
Transactions
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: J. Mondal, P.
Saikiran, S. R. B, D. J. Morgan, D. B. Shinde, Z. Lai and N. Lingaiah, Dalton Trans., 2019, DOI:
10.1039/C9DT01190K.
This is an Accepted Manuscript, which has been through the
Volume 45 Number
1 7 January 2016 Pages 1–398
Royal Society of Chemistry peer review process and has been
accepted for publication.
Dalton
Transactions
Accepted Manuscripts are published online shortly after
An international journal of inorganic chemistry
www.rsc.org/dalton
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1477-9226
PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
framework
a Zr-metal–organic
rsc.li/dalton

Page 1 of 26
Dalton Transactions
View Article Online
Metal-Organic-Framework Derived Co-Pd Bond is Preferred over Fe-Pd
DOI: 10.1039/C9DT01190K
for Reductive Upgrading of Furfural to Tetrahydrofurfuryl alcohol†
Saikiran Pendem,a,b Bolla Srinivasa Rao,a,b David J. Morgan,c Digambar B. Shinde,d Zhiping
Lai,d Nakka Lingaiah,a,b and John Mondal*a,b
aCatalysis and fine chemicals Division, CSIR-Indian Institute of Chemical Technology,
Uppal
Road,
Hyderabad-500007,
India,
Email:
johncuchem@gmail.com,
johnmondal@iict.res.in
bAcSIR-Indian Institute of Chemical Technology, Hyderabad-500007 (India)
cCardiff Catalysis Institute, School of Chemistry, Cardiff University, Park Place, Cardiff,
CF10 3AT. UK
dDivision of Physical Science and Engineering, King Abdullah University of Science and
Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
ABSTRACT:
The function of combined noble-transition metal catalysts to produce a wide range of
important nonpetroleum based chemicals from biomass derived furfural as platform molecule
has garnered colossal research interest for the urgent demand of sustainable and clean fuels.
In this respect herein, we report palladium modified Metal-Organic-Framework (MOF)
assisted preparation of PdCo3O4 and PdFe3O4 nanoparticles encapsulated in a graphitic N-
doped carbon (NC) matrix via facile in situ thermolysis, to have a change in selectivity with
superior catalytic activity for reductive upgrading of biomass-derived furfural (FA). Under
the optimized reaction conditions, newly designed PdCo3O4@NC catalyst exhibited highly
efficient catalytic performance in the hydrogenation of furfural, providing 100% furfural
conversion with an exclusive 95% yield of Tetrahydrofurfuryl alcohol (THFAL). In contrast,
the as-synthesized Pd-Fe3O4@NC afforded 70% THFAL yield after 8 h reaction course with
consecutive four recycling tests. With the evidence of different characterization analysis data
(XPS, H2-TPR) of nanohybrid we can emphasise that the presence of PdCo-Nx active sites
and the multiple synergistic effect between Co3O4 and Pd (II), Co3O4 and Pd0 as well as
presence of N in the carbonaceous matrix responsible for the superior catalytic activity and
improved catalyst stability. Our strategy provides a facile design and synthesis process of
1

Dalton Transactions
Page 2 of 26
View Article Online
noble-transition metal alloy as superior biomass refining robust catalyst via noble metal
DOI: 10.1039/C9DT01190K
modified MOFs as precursors.
KEYWORDS: N-doped carbon • Co3O4 • Fe3O4 • Metal-Organic-Framework•
Tetrahydrofurfuryl alcohol • Hydrogenation of furfural • Biomass
INTRODUCTION:
Currently, the modern world requires the sustainable production of biomass-derived
chemicals such as fuels, fuel additives and value-added chemicals due to the diminishing of
fossil feedstock reserves. Researchers have been focusing on finding sustainable ways to
substitute fossil-derived feedstocks with residual biological matter such as crops, scrap wood,
mill residuals, and other biomass resources.1-4 In our present study, Furfural used as raw
material to produce tetrahydrofurfuryl alcohol (THFAL), which is one of the typical chemical
products derived from furfural and furfuryl alcohol (FAL). THFAL is completely miscible
with water and used as green solvent in agricultural and industrial applications, It can also be
converted into to various chemicals such as 1,5-pentanediol (1,5-PeD) an important monomer
in the plastics industry, 1-pentanol (1-PeOH), tetrahydropyran (THP), tetrahydro-2-pyranone
(THP-2-one), methyl tetrahydrofuran, 2-pentanol, tetrahydrofuran, 1-butanol (1-BuOH), 1,2-
pentanediol5 and it is clearly pronouncing the importance of THFAL production. Salnikova et
al. Reported selective hydrogenation of furfural to FAL using Pd/Fe3O4/HPS as a catalyst, the
conversion of furfural was > 95% with selectivity for furfuryl alcohol > 94%. Whereas these
processes required high pressure about 6.0 MPa.6 Compared with Pd, Ru based catalysts
show poor catalytic activity to hydrogenate C=C bonds in the aromatic ring of furfural.7-9
Very recently, Rodríguez-Ramos et al. reported hydrogenation of furfural using a series of
Ru-based catalysts under very mild conditions. Although the conversion of furfural was 93%,
the selectivity toward total hydrogenation THFAL very poor.8 Nowadays, Metal-organic
frameworks (MOFs) derived nanostructural materials have been received enormous attention
as a novel class of porous carbon materials by providing wide-range of various structural
materials, especially in heterogeneous catalysis. MOFs have also been utilized in various
research fields, such as energy storage,10-12 supercapacitors,13 gas separation,14 oxygen
reduction reactions,15 CO2 reduction,16,17 oxidation reactions,18 oxygen evolution reactions,19
biomass refinement20,21 and so on. And their efficient catalytic activity is due to the
modifiable particle, pore sizes, controllable shapes,18 and high specific surface areas with
unique structures. Moreover, these materials are well known for developing N, P and S like
2

Page 3 of 26
Dalton Transactions
View Article Online
hetero atom rich nanostructural carbon materials, and metal or metal oxide loaded porous
DOI: 10.1039/C9DT01190K
carbons and N-doped porous carbons with novel characteristics via pyrolysis process by
acting as self-sacrificed template/precursor.12,22-24 Recently, Guozhong Wang et al. reported
the Ni based catalyst derived from MOFs via a sacrificial template method for the
hydrogenation of furfural to THFAL with good catalytic activity by consuming very minimal
amount of 0.2 mmol furfural.25 Introduction of nitrogen like heteroatoms into carbon
materials decreases the charge transfer resistance to improve catalytic performance by a
synergistic effect22 between carbon and the heteroatom. 2-methylimidazole ligands of zeolitic
imidazolate frameworks (ZIFs) are the unique source for developing carbon and nitrogen-rich
(N-rich) MOFs derived porous nanostructural catalysts via direct carbonization.24,26,27 Pd-3d
transition metal oxides@N-doped Carbon type catalysts are efficient for selective and total
hydrogenation of biomass-derived furfural. The selectivity of hydrogenation of furfural can
be varied with 3d transition metal oxides. In the present study, Pd-Fe3O4@NC tends to
hydrogenate C=O functional group over furon ring C=C bonds of furfural to produce furfuryl
alcohol (FAL). FAL has been noticed as a valuable chemical compound with a wide range of
applications such as foundry binders, precursors of resins.28 Additionally, FAL can be used in
the production of THFAL.29 Interestingly, we noticed that the Pd-Co3O4@NC catalyst shown
efficient catalytic activity towards hydrogenate furan aromatic ring C=C and C=O bonds of
furfural with 95% yield with excellent catalyst durability and much higher activity with up to
4th catalytic run indicates the good recyclability. Overally, it is pronouncing that the Co3O4
support is more effective for the total hydrogenation of furfural to produce THFAL over
Fe3O4 support. These Pd-Fe3O4 and Pd-Co3O4 decorated on porous nitrogen-doped carbon
catalysts (Pd-Fe3O4@NC and Pd-Co3O4@NC) developed via direct thermal decomposition in
H2 flow of ZIF solid contain with an N-rich organic linker. The specific textural, chemical
characteristics and atomic-level relationship between structure and catalysis of PdCo3O4@NC
have been widely investigated by performing powder x-ray diffraction (P-XRD), high-
resolution transmission electron microscopy (HR-TEM), scanning electron microscopy
(SEM), temperature-programmed reduction (TPR), nitrogen adsorption-desorption, x-ray
photoelectron spectroscopy (XPS) and Raman. On the basis of the detailed investigation with
characteristic techniques, including H2TPR and XPS, the active catalytic performance and
durability of Pd-Co3O4@NC towards the hydrogenation of furfural to THFAL with 95%
yield and good recyclability are can be attributed to the multiple intrinsic synergistic effect
between Co3O4 and Pd(II), Co3O4 and Pd0 as well as presence of PdCo-Nx active sites in a
carbonaceous matrix.
3

Dalton Transactions
Page 4 of 26
View Article Online
DOI: 10.1039/C9DT01190K
EXPERIMENTAL:
Catalyst Characterization:
Powder X-ray diffraction (PXRD) patterns of the different samples were recorded with a
Bruker D8 Advance X-ray diffractometer operated at a voltage of 40 kV and a current of 40
mA using Ni-filtered Cu Kα (λ=0.15406 nm) radiation. High-resolution transmission electron
microscopy (HR-TEM) images were recorded from a JEOL JEM 2010 transmission electron
microscope with an operating voltage of 200 kV equipped with a field emission gun. Field
emission scanning electron microscopy images of the samples were obtained using a JEOL
JEM 6700 field emission scanning electron microscope (FE-SEM). Raman spectra of the
samples were recorded using a LabRAM HR800 confocal microscope Raman system
(HoribaJobin Yvon) with an Ar ion laser operating at 632 nm. Nitrogen sorption isotherms
were measured at 77 K with an autosorbiQ automated gas sorption analyser (Quantachrome
Instruments, USA). Before the measurements, the samples were degassed under vacuum at
200°C for 8 h. The Brunauer–Emmett–Teller (BET) method was utilized to determine the
specific surface area using adsorption data in a relative pressure (P/P0) range of 0.05–0.30.
The total pore volumes and pore size distribution curves were obtained from the adsorption
branches using the nonlocal density functional theory (NLDFT) method. X-ray photoelectron
spectroscopy (XPS) was performed on a Kratos Axis Ultra system using monochromatic Al
K radiation, with a photon energy of 1486.6 eV. High resolution spectra were collected
using a 20 eV pass energy, whilst survey spectra were collected at 160 eV, with step sizes of
0.1 and 1 eV respectively. The H2-TPR analysis was carried out in a quartz micro-reactor
interfaced to a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD)
unit. Prior to TPR analysis, the catalyst was degassed at 300ºC in helium gas for 30 min and
then cooled to room temperature. The helium gas was switched to 4.97% H2 in argon with a
flow rate of 30 mL min-1 and the temperature was increased to 900ºC at a ramping rate of 5ºC
min- 1.
Catalyst Preparation:
Synthesis of stabilized Pd nanoparticles solution:
600 mg Polyvinylpyrrolidone (PVP) was dissolved in 180 mL methanol then Palladium
acetate trimmer solution (80 mg Palladium acetate trimmer dissolved in 6.2 mL H2O) was
slowly added with continuous stirring at room temperature, after that this mixture was
4

Page 5 of 26
Dalton Transactions
View Article Online
refluxed at 70°C in air for 3 h, resulting mixture was dried using rota evaporation, obtained
DOI: 10.1039/C9DT01190K
black solid Pd stabilized nanoparticles material was dissolved in 50 mL H2O.
Metal-Organic-Framework derived synthesis of Pd-Fe3O4 & Pd-Co3O4 nanoparticles on
N-Doped Porous Carbon Sheets:
2-methylimidazole (1.312g) and PVP (0.08g) was dissolved in 100 mL methanol, then this
solution was slowly added into metal nitrate solution (Co(NO3)2.6H2O (4 mmol, 1.164g)
dissolved in 100 mL methanol) with continuous stirring at room temperature, after that
stabilised Pd nanoparticles solution (16 mL) was slowly dropwise added into previous
solution and stirred for 45 minutes at room temperature, resulting mixture was supposed to
age for 24 h, obtained solution was washed several times with methanol using centrifugation
and dried in air, and then this solid material was heated at 120°C (10°C min-1) for 1 h then
300°C (10°C min-1) for 2 h in H2 flow. The obtained solid component was assigned as Pd-
Co3O4@NC sheets. Pd-Fe@NC was also prepared using the same synthesis process, the
obtained component using Fe(NO3)3.9H2O (Fe(NO3)3.9H2O (4 mmol, 1.616g) dissolved in
100 mL methanol) as metal nitrate solution in the above procedure assigned as Pd-
Fe3O4@NC by following the previously reported np-PtFe/NPCS synthesis by Chen et.al30a.
Additionally, we have developed a series of CuFe@NC, CuCo@NC, Co@NC and Fe@NC
catalysts. CuFe@NC and CuCo@NC were developed by adding the stabilized Cu
nanoparticles, which preparation method is similar to the synthesis of stabilized Pd
nanoparticles solution (0.11 mmol of Cu(NO3)2.3H2O was used), instead of stabilized Pd
nanoparticles solution. Co@NC, Fe@NC were prepared by adopting a similar synthesis
process where we avoided the addition of stabilized Pd and Cu nanoparticles solution.
Activity Test:
All the hydrogenation reactions of furfural were performed in a stainless-steel Parr autoclave
inbuilt with a 190 pressure gauge setup lined with Teflon (50 mL), for a typical
hydrogenation of furfural, 50 mL Parr autoclave was charged with a mixture of furfural (1
mmol), isopropanol (25 mL), 70 mg catalyst and the reactor was sealed with an overhead
stirrer and purged four times with molecular hydrogen (H2). Then the reactor was pressurized
with H2 (20 bar) and heated at 150°C with stirring at a speed of 700 rpm for 6 h. Then the
reactor was stopped and the pressure in the autoclave was slowly released after the reactor
cooled to room temperature. The solid catalyst was recovered from the reaction mixture by
centrifugation and the isolated liquid reaction mixture was analyzed by chromatography
5

Dalton Transactions
Page 6 of 26
(GC). GC (Shimadzu 2010) equipped contain with a flame ionization 200 detector (FIDV)i,ewnAorticle Online
DOI: 10.1039/C9DT01190K
wax capillary column (length: 30 201 m diameter: 0.25 mm), and gas chromatography-mass
spectrometry (GC-MS) (Shimadzu, 202 GCMS-QP2010S) were utilized for quantitative
analysis and product detection in the presence of 1,4-dichlorobenzene as an internal standard.
In the GC and GC-MS analysis, the initial column temperature of 50°C was held for 2 min,
after that the temperature was programmed as 100°C with a ramp rate of 5°C m-1 and held for
2 min, again the temperature was ramped at 10°C m-1 until 250°C was reached and held for 2
min. in addition, the injector, detector temperatures were fixed to 250°C and 270°C,
respectively.
Hot Filtration Test:
In order to confirm the heterogeneous and robust nature of our newly developed
PdCo3O4@NC nanohybrid we have conducted a hot filtration test in a 50 mL Parr autoclave
charged with a mixture of furfural (1 mmol), isopropanol (25 mL), 70 mg catalyst and the
reactor was sealed with an overhead stirrer and pressurized with H2 (20 bar) and heated at
150°C with stirring at a speed of 700 rpm for 2 h. After reaction proceeded for 2 h, the
catalyst was isolated from the hot reaction mixture by centrifugation and sample prepared
from filtrate for GC analysis, 100% furfural conversion with 75% yield of THFAL was
noticed over PdCo3O4@NC, then we have performed same catalytic reaction at identical
reaction conditions with collected filtrate for an additional 6 h, and no considerable
hydrogenation of filtrate was noticed by GC analysis indicating that there is no leaching of
nanoparticles due to nanoparticles strongly anchored with N-doped carbon matrix
pronouncing the robust nature of PdCo3O4@NC.
RESULTS AND DISCUSSION:
The successful development of robust hollow structured PdCo3O4@NC nanohybrid was
achieved in a systematic and easy catalyst preparation strategy as illustrated in Scheme 1.
Initially, PVP-Pd@ZIF-67 composite was developed by consuming 2-methylimidazole as a
self-sacrificed template, Co(NO3)2.6H2O and Palladium acetate trimmer involved as a metal
source at room temperature, in the overall synthesis process PVP served as a stabilizer in Pd
nanoparticle synthesis and developing nanocomposite. The deep washing of prepared
composite, using centrifugation at 10,000 rpm, with methanol removes the water molecules
(moisture) loosely adsorbed on solidified PVP-Pd@ZIF-67 composite, and which makes the
drying process easy to obtain well dried solid PVP-Pd@ZIF-67 composite. The characteristic
6

Page 7 of 26
Dalton Transactions
FE-SEM of the solid nanocomposite of PVP-Pd@ZIF-67 shown in Figure SD1OIE: 1S0.1I0.3V9iTe/wChA9erDticTl0e1O1n9l0inKe
crystalline phases of the as-synthesized Co-ZIF were nicely matched with simulated XRD
data (Figure S2a ESI) as obtained using Rietveld refinement (conducted by Materials studio,
Accelrys Software Inc.) confirming that as-synthesized Co-ZIF comprises the crystal
structure of ZIF-67. Herein, As final step we conducted the reductive carbonization of solid
PVP-Pd@ZIF-67 under the molecular hydrogen gas flow at pre-programed-temperature
(120°C, 10°C min-1 than 300°C, 10°C min-1) to obtain Pd-Co3O4 encapsulate in graphitic N-
doped carbon matrix denoted as PdCo3O4@NC, and which preparation strategy avoids the
additional steps need to be involved to succeed required Pd0 state.30b During the
decomposition of nanocomposite, the organic ligands from the ZIF are condensed to form
nitrogen doped porous carbon matrix, on other side the formation of Co3O4 begins as raising
temperature to 300°C from Co2+ which further interact with Pd to produce Pd-Co3O4, which
were in situ confined into N-doped carbon matrix, leading to homogeneous dispersion of the
Pd-Co3O4 on carbon matrix with controlled generation of highly catalytically PdCo-Nx active
sites with an effective approach for graphitization of amorphous carbon by solid-state
transformation method. The Co, Fe & Pd contents in PdCo3O4@NC and PdFe3O4@NC
materials are 1.45, 1.29, 0.039 and 0.036 mmol g-1, respectively, as measured by inductively
coupled plasma atomic emission spectrometry (ICP-AES) analysis.
Scheme 1: Schematic illustration for metal-organic-framework mediated synthesis of Pd-
Fe3O4 & Pd-Co3O4 nanoparticles on N-doped porous carbon sheets
7

Dalton Transactions
Page 8 of 26
View Article Online
The formation of Co3O4 and Fe3O4 confirmed by the X-ray diffraction analysis of the
DOI: 10.1039/C9DT01190K
prepared samples, the X-ray diffractograms were scanned between wide angles of 5-80° (2θ).
Pd-Fe3O4@NC sample exhibited six peaks, the absence of other phases of iron oxide,
characteristic for the magnetic cubic structure of Fe3O4 (Figure 1) phase at 2θ values of 30.3°,
35.7°, 43.3°, 54.1°, 57.4° and 62.9° (JCPDS 19-0629) with the corresponding diffraction
planes of (220), (311), (400), (422), (511) and (440).31 There is no noticeable Pd (0)
diffraction peak for Pd-Fe3O4@NC and a very weak Pd(111) diffraction peak for Pd-
Co3O4@NC indicative of finely dispersed Pd (0) and its existence in both catalysts confirmed
by XPS analysis (Figure 4) and H2-TPR (Figure 3). Pd- Co3O4@NC exhibited characteristic
peaks of Co3O4 phase at 2θ values of 36.6° and 44.5° (JCPDS-ICDD 9-418) with the
corresponding to the (311) and (400) diffraction planes indicating the successful formation of
high crystalline quality metal oxide (Co3O4) (Figure 2).32 Surface properties of catalysts could
be determined using Nitrogen adsorption-desorption isotherm. The obtained isotherm of both
PdFe3O4@NC and PdCo3O4@NC catalysts are corresponding to a type (II) with H3
hysteresis in the Brunauer classification confirms the existence of inter-particle void spaces,
and it does not show any limiting adsorption at high relative pressures (P/P0). The Brunauer-
Emmett-Teller surface area (SBET) for Pd-Fe3O4@NC and Pd-Co3O4@NC was found to be
60.96 m2/g and 109.07 m2/g, respectively. The pore size distribution of PdCo3O4@NC was
measured to be 1.70 nm, which further confirms its microporous nanostructure. Interestingly,
a comparable pore size distribution centered at 1.70 for PdFe3O4@NC, the average pore sizes
of both the catalysts are 1.70 nm which are in micropore region, due to similar dense
nanoparticles serves as templates to generate microporous N-doped carbon nanostructure in
both catalysts, and the additional pores, which are formed from uncontrolled aggregated
nanoparticles of Fe-ZIFs thermal treatment in H2 flow, were noticed from PdFe3O4@NC as
well. (Figure S3, S4, ESI).
8

Page 9 of 26
Dalton Transactions
View Article Online
DOI: 10.1039/C9DT01190K
Figure 1: Wide angle powder XRD patterns (a) and (b), N2 adsorption/desorption isotherms
(c) and (d), of Pd-Co3O4@NC and Pd-Fe3O4@NC, respectively.
Nanostructures, Particle size and morphology of Pd-Fe3O4@NC and Pd-Co3O4@NC
composites evidently studied by high-resolution transmission electron microscopy (HR-
TEM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM)
analytical techniques. The morphology of Pd-Fe3O4@NC and Pd-Co3O4@NC is clearly
categorized by the FE-SEM images (Figure S5 ESI). As presented in Figure S5b ESI, it is
seen that the Pd-Fe3O4 nanoparticles decorated on N-doped matrix are composed of flake
type sheets. But in the case of the Pd-Co3O4@NC compound consistency of closely packed
spherical shape of particles very clearly noticed from SEM images (Figure S5a ESI).
Actually, Pd-Fe3O4 nanoparticles tend to form aggregates due to high surface energy, and
high surface interaction between the nanoparticles and large specific surface area. In the TEM
images (Figure 2), uniformly distributed darker spots of spherical metal oxides nanoparticles
surrounded by lighter regions of n-doped carbon matrix in Pd-Fe3O4@NC and Pd-
Co3O4@NC are developed by aggregation process of metal oxides nanoparticles with an
average size range of 11.9-21.8 (Fe3O4) and 20-40 nm (Co3O4). As shown in Figure 2b & 2d,
HR-TEM images along with the corresponding Elemental mapping data are clearly
9

Dalton Transactions
Page 10 of 26
View Article Online
representing the hollow metal oxide (Co3O4, Fe3O4) polycrystals, the distinguished crystalline
DOI: 10.1039/C9DT01190K
lattice spacing about 0.30nm attributed to (220) diffraction planes omitted from
crystallographic planes of the inverse spinel Fe3O4 nanoparticles. Parallel fringes having d-
spacing of ∼0.204 and 0.248nm, respectively are corresponding to the (400) and (311)
diffraction planes of the normal spinel Co3O4 nanoparticles which is similar to powder XRD
crystalline reflections. The existence and homogeneous distribution of each element of Pd-
Co3O4@NC (Pd, Co, C, N, O) and Pd-Fe3O4@NC (Pd, Fe, C, N, O) clearly observed from
corresponding high angle annular dark field scanning transmission electron microscopy
elemental mapping data of nanohybrids (Figure 2 e, f )
Figure 2: HR-TEM images with corresponding Elemental mapping data (a, b & e) of Pd-
Co3O4@NC, (c, d & f) of Pd-Fe3O4@NC, respectively.
As shown in Figure 3, the H2-TPR of Pd-Fe3O4@NC and Pd-Co3O4@NC is indicating the
successful loading of palladium, and the formation of Fe3O4 and Co3O4, respectively. The H2-
TPR of Pd-Fe3O4@NC exhibited a peak about 120-207ºC corresponding to the reduction of
Pd-O to Pd, and a broad peak appeared at 470-840ºC is due to overlapping of Fe3O4 to FeO
peak at 420-660ºC and FeO to Fe peak at 660-850ºC revealing the consistency of Fe3O4
phase.33 Usually, the discrepancy in chemical states of Pd nanoparticles directs to different
redox properties. The Pd-Co3O4@NC exhibited a broad reduction peak of Pd(II) to Pd at 104-
10

Page 11 of 26
Dalton Transactions
View Article Online
315ºC with slow uptake by consuming H2 continuously is due to inhibition of in-situ
DOI: 10.1039/C9DT01190K
formation of PdO via lowering the reduction temperature of Pd-O to Pd by Co3O4.
Interestingly, Pd(II) reduction temperature shifted towards higher temperature indicating the
stabilization of Pd(II) due to the formation of Pd-O-Co bond between Pd(II) and Co3O4,34 and
it is pronouncing that the existence of electronic interaction between Pd and Co. The broad
peak and a small peak at 299-600ºC is due to two-step reduction process of Co3O4, the first
peak is due to Co3O4 to CoO reduction and the second peak is due to the subsequent
reduction of CoO to Co.
Figure 3: H2-TPR profiles of Pd-Co3O4@NC & Pd-Fe3O4@NC, respectively.
The electronic structure and chemical state of Pd nanoparticles in Pd-Co3O4@NC and Pd-
Fe3O4@NC catalysts, and surface electronic property and elemental compositions were
evidently identified by XPS investigation of Pd-3d, Co-2p, Fe-2p and N1s of Pd-Co3O4@NC
and Pd-Fe3O4@NC (Figure 4) at their corresponding binding energies. The N-1s XPS
spectrum of Pd-Co3O4@NC exhibited a broad peak which could be resolved into two
components attributed to pyridinic N at 399.1 eV and graphitic N at 400.4 eV. The pyridinic
N peak resulted from Pd-Co3O4@NC shifted towards the high binding energy about ∼0.3 eV
compared with Pd-Fe3O4@NC revealing that the pyridinic N (Lewis base) strong interactions
with Co3O4 confirming the successful formation of the N-doped carbon matrix and it is well
known that the synergistic effect between Pd and N play an additional role in enhancing the
11

Dalton Transactions
Page 12 of 26
catalytic activity.35,36 whereas, in Pd-Fe3O4@NC the N-1s binding energy of pyridinViciew NArticle Online
DOI: 10.1039/C9DT01190K
located at 398.8 eV (Figure 4d). As shown in Figure 4a, the Pd-3d XPS spectra of
PdCo3O4@NC exhibited a sharp doublet with the 3d5/2 peak centred at 335.3 eV w
corresponding to Pd0 (Figure 4a). Interactions between Pd0 and Co3O4 can be attributed to
intrinsic synergistic effect developed by charge transfer of electrons between Pd and Co,35
and shown enhanced activity in the hydrogenation of furfural, and one more doublet with a
Pd5/2 peak at 338.0eV corresponding to Pd(II) which connected with Co3O4.37 Moreover, we
also identified that the electronic structural properties of Co3O4 in PdCo3O4@NC nanohybrid
is quite similar to those investigated by Xihong Lu et al. The investigation of Co-2p XP
spectra at binding energy of 779.6 eV revealing (Figure 4c) that as lattice oxygen atoms
containing Co3O4 (O 1s, Figure S6 ESI) interacting with Pd(II) nanoparticles the Lewis acidic
nature of Co3O4 enhances due to synergistic effect between Co3O4 and Pd(II) by electron
transport from Co3O4 to Pd(II), and it pays a key role in favoring the interactions between
carbonyl group of furfural with Co3O4 to succeed coordination bond as well in hydrogenation
process in presence of Pd0 via hydrogen dissociation and spillover on Co oxide encapsulated
in graphitic N-doped carbon matrix.38,39 In the case of the Pd-Fe3O4@NC catalyst Pd-3d XPS
spectra exhibited metallic Pd as indicated by the 3d5/2 signal at, 334.9 eV this bulk like value
suggests that either the particles are bigger, exhibiting more bulk like properties, or there is
little considerable interactions between Pd and Fe3O4 lowers the charge transport between the
Pd and Fe3O4 which can be suppress the capability of ring hydrogenation of furfural, and the
second one at lower binding energies compare with Pd-Co3O4, binding energy of 337.2eV
indicating the existence of Pd(II). The Fe 2p XPS spectra indicates no other iron oxides are
present, with the Fe2p3/2 peak at 710 (Fe 2p3/2), along with satellite peaks can be attributed to
the magnetite (Fe3O4) (Figure 4b).40
12

Page 13 of 26
Dalton Transactions
View Article Online
DOI: 10.1039/C9DT01190K
XPS: Figure 4: Fitted Pd-3d (a), Fe-2p (b), Co-2p (c), N-1s (d), XP spectra of Pd-
Fe3O4@NC & Pd-Co3O4@NC, respectively.
In addition to powder XRD the formation of Co3O4 and Fe3O4 phases is confirmed by the
Raman spectroscopy analysis of untainted Pd-Fe3O4@NC and Pd-Co3O4@NC catalysts. The
Raman spectra of Pd-Fe3O4@NC exhibited one broadband around 660 cm-1 corresponding to
A1g mode and two broadbands around 1359 and 1583 cm-1 are attributed to the vibration
modes of Fe3O4 phase and hematite, respectively.41,42 As space group theory predict Γ=A1g +
Eg + 3F2g vibration modes are Raman active modes as “Fd3m” symmetry for the Co3O4
13

Dalton Transactions
Page 14 of 26
View Article Online
normal spinel configuration, the Pd- Co3O4@NC nanoparticles exhibited five characteristic
DOI: 10.1039/C9DT01190K
bands around 197, 484, 524, 621 and 690 cm-1 can be attributed to Raman active F2g, Eg,
2F2g and A1g vibration modes of normal spinel Co3O4 phase, respectively (Figure 5). Out of
five Raman active vibrational modes, the F2g (197 cm-1) vibration mode corresponding to
CoO6 scissoring vibration mode, whereas Eg (484 cm-1), 2F2g (524, 621 cm-1) and A1g (690
cm-1) are exhibit Co-O symmetric stretching vibration.43-45
Figure 5: Raman spectra of Pd-Co3O4@NC (a) & Pd-Fe3O4@NC (b), respectively.
Catalytic activity for reductive upgrading of bio-mass derived furfural:
To evaluate the catalytic activity of the as-synthesized PdCo3O4@NC we have conducted
Hydrogenation of furfural. During the course of the reaction, we have noticed the formation
of the variety of products from furfural over the PdFe3O4@NC and PdCo3O4@NC catalyst
(Scheme 2). The formation of THFAL from furfural involves two subsequent steps.
hydrogenating furan aromatic ring C=C is hard compared with C=O bonds of furfural as
presented in plausible mechanism Scheme 2, in the first step furfural interact with a catalyst
to produce furfuryl alcohol (FAL), subsequently, second step initiate to hydrogenate furon
ring of furfuryl alcohol to yield desired THFAL. Further THFAL interaction with metal
involves in hydrogenolysis process to yield MeTHF which is a by-product of furfural
hydrogenation using PdFe3O4@NC and PdCo3O4@NC as a catalyst. Our catalytic study
experiments evidently proved the plausible mechanism. The beginning of catalytic activity
study is the comparison, and the effect of reaction time, temperature and pressure on the
catalytic activity of PdFe3O4@NC and PdCo3O4@NC (Figure 6). As shown in Figure 6b in
presence of PdFe3O4@NC, at initial 1 h time period the product yield of THFAL, FAL
14

Page 15 of 26
Dalton Transactions
noticed as 28% and 71%, respectively, along with the formation of side products (MeTHVFie,w2Ar-ticle Online
DOI: 10.1039/C9DT01190K
Methylfuron) with 100% conversion. Herein we noticed that the THFAL yield further
enhanced to 70% by hydrogenating FAL to THFAL as expanded the time period to 8 h at
identical 20 bar H2, 150°C. Interestingly, the PdCo3O4@NC nanohybrid exhibited complete
conversion of furfural with the 60% yield of THFAL and 33% yield of FAL at reaction time
period for 1 h. With the progress of reaction from 1 h to 8 h during the optimization of
reaction time at fixed H2 pressure (20 bar) and temperature (150°C) gradual increase in the
product yield of THFAL with the maximum of 95% up to 6 h noticed which indicating that
the active sites are initially engaged in interacting with furfural carbonyl group Pd(II) in
presence of Pd0 to yield FAL which subsequently undergoes to produce THFAL due to the
total hydrogenation of furfural to THFAL proceeds via hydrogenating C=O and furan
aromatic ring C=C bonds of furfural, respectively, the C=O bond is less stable and easy to
hydrogenate than furan aromatic ring C=C bonds (Scheme S1 ESI)46,47,25 and the further
extension of time period to 8 h declined the THFAL yield to 88% which can be ascribed to
the hydrodeoxygenation of THFAL into undesired side product methyl tetrahydrofuran
(MeTHF) in presence of PdCo3O4@NC with the complete conversion as well (Figure 6a).
15

Dalton Transactions
Page 16 of 26
View Article Online
DOI: 10.1039/C9DT01190K
Figure 6: Evolution of reactant and product distributions as a function of time over (a)
PdCo3O4@NC, (b) PdFe3O4@NC. Reaction conditions: furfural (1 mmol), isopropanol (25
mL), 70 mg catalyst, H2 (20 bar), 150°C.
A similar scenario has been identified while investigating temperature and pressure influence
on the catalytic activity of both catalysts, the desired product yield of THFAL and the side
products yield affected as well. As the temperature increase 90 to 200°C at the fixed H2
pressure of 20 bar, the maximum product yield of THFAL with 95% achieved at 150°C for
PdCo3O4@NC and quite dissimilar from PdFe3O4@NC further increase of temperature from
this point the continuous decline in product yield of THFAL observed on another side
MeTHF percentage of yield gradually increased to 41% via hydrodeoxygenation process at
high temperature (220°C) (Figure 7c). High product yield (88%) of FAL has been noticed in
presence of PdFe3O4@NC at lower temperatures (90°C), and as raising the temperature from
lower to higher (200°C) the yield of THFAL reached 65%, further involved in the
16

Page 17 of 26
Dalton Transactions
View Article Online
hydrogenolysis process to yield MeTHF at 220°C (Figure 7d). Eventually, after an
DOI: 10.1039/C9DT01190K
investigation of temperature effect on the catalytic activity of catalysts, the pressure influence
of H2 pressure ranging from 15-30 bar has been examined. With increasing the H2 pressure
from 15-25 bar, the required abundance of dissolved H2 in the reaction mixture was achieved
at 25 bar and obtained the huge yield of THFAL with 95% at 150°C and 6 h reaction time
period for PdCo3O4@NC (Figure 7a). In presence of PdFe3O4@NC furfural converted into
FAL with 71% product yield at an initial H2 pressure of 15 bar and the maximum yield of
THFAL noticed at 30 bar due to further hydrogenation of FAL at high pressure (H2 30 bar)
(Figure 7b).
Figure 7: Influence of H2 pressure (a & b) & temperature (c & d) on PdCo3O4@NC &
PdFe3O4@NC, respectively. Reaction conditions: furfural (1 mmol), isopropanol (25 mL), 70
mg catalyst, H2 (20 bar), 6 h.
17

Dalton Transactions
Page 18 of 26
View Article Online
DOI: 10.1039/C9DT01190K
Scheme 2: Plausible mechanistic two step pathway of total hydrogenation of furfural to
tetrahydrofurfurylalcohol over PdCo3O4@NC.
In order to evaluate the superior catalytic activity of PdCo3O4@NC towards the
hydrogenation of furfural to THFAL, we have compared reported Pd-Based Catalysts
catalytic activity for conversion of furfural to THFAL (Table S1 ESI), additionally, we have
developed a series of catalysts including CuFe@NC, CuCo@NC, Co@NC and Fe@NC by
following a similar synthesis procedure involved in the development of PdCo3O4@NC
nanohybrid. From the comparison study as depicted in Figure 8 we have achieved 100%,
100%, 38%, 23% furfural conversion from CuFe@NC, CuCo@NC, Co@NC and Fe@NC,
respectively, at optimized reaction conditions. Especially the yields of THFAL from furfural
for corresponding catalysts are noticed as very low compared with PdCo3O4@NC. Fe@NC,
Co@NC provided much lower yields of THFAL 3% and 12%, respectively. CuFe@NC and
CuCo@NC catalysts exhibited improved catalytic activity and the yields of THFA are 27%
and 42%, respectively, with complete conversion of furfural Which conclude that the Cu
promoted Co/Fe and Co/Fe are less active in N-doped carbon matrix to achieve desired
18

Page 19 of 26
Dalton Transactions
View Article Online
product THFAL suggesting the importance of enhanced Lewis acidic nature oDfOCI: 1o03.1O0349/Cb9yDT01190K
synergistic effect between Co3O4 and Pd(II) in PdCo-Nx active sites to achieve the
interactions between carbonyl group of furfural with metal oxide in hydrogenation process of
furfural. But in the case of PdFe3O4@NC exhibited considerably good yields at first reaction
run (45%, 6 h) although which is unstable indicating the impact of Pd0 in achieving enhanced
THFAL yields. We have also compared the catalytic activity of PdCo3O4@NC-400
PdCo3O4@NC-500 PdCo3O4@NC-600 catalysts developed by pyrolysing the PVP-Pd@ZIF-
67 at 400, 500 and 600°C temperatures under continuous molecular hydrogen flow. We
noticed that as pyrolysis temperature increased the catalytic activity of PdCo3O4@NC get
diminished, THFAL yield dropped from 94 to 72% (Table S3, ESI). The diminishment in
catalytic performance could be attributed to the detachment of catalytic metal active sites
from the carbonaceous matrix as with the increase pyrolysis temperature loss of carbon and
rupture of organic framework is happened. Carbon layers play a pivotal role which wraps the
catalytic active sites more strongly thereby preventing the leaching of metal ions during
reaction. As a final step in the comparison study, we have conducted the hydrogenation
reaction of furfural in inert conditions (presence of N2, 5 bar) too for PdCo3O4@NC and
PdFe3O4@NC, and the resulted yields of THFA are 45% and 35%, respectively (Figure 8).
However, from comparison investigation conclude that the PdCo3O4@NC nanohybrid
exhibited superior catalytic activity with exclusive yields of THFA (95%) (Figure 6a).
Figure 8: Reaction conditions: furfural (1 mmol), isopropanol (25 mL), 70 mg catalyst, H2
(20 bar), 6 h for CuFe@NC, CuCo@NC, Co@NC and Fe@NC. Inert reaction conditions:
furfural (1 mmol), isopropanol (25 mL), 70 mg catalyst, inert atmosphere (N2, 5 bar), 6 h for
PdCo@NC and PdFe@NC.
19

Dalton Transactions
Page 20 of 26
View Article Online
In order to affirm the stability of the catalyst, we have done XPS analysis at 3d-Pd region of
DOI: 10.1039/C9DT01190K
used catalysts along with reusability test as well. Interestingly, we noticed that the
PdCo3O4@NC nanohybrid exhibited a sharp doublet with high intensity similar with fresh
catalyst at the binding energy of ~340.5 and ~335.4 eV corresponding to the Pd0 interacted
with Co3O4 further confirming the negligible leaching of Pd and the robust nature of Pd-
Co3O4@NC nanohybrid, additionally, these results well consistent with the hot filtration test.
Whereas Pd-3d XPS spectra of PdFe3O4@NC (Figure 10a) very clearly indicating the huge
amount of leaching of Pd from the catalyst due to the existence of Pd in the form of bulk
Pd(0) (3d3/2 = 40.2 eV; 3d5/2 = 334.9 eV) which is loosely binded on Fe3O4@NC surface with
less interactions between Pd and Fe3O4 diminishes the stability of catalyst. In order to map
the leaching we have conducted further Inductive Couple Plasma-Atomic Emission
Spectroscopy (ICP-AES) analysis which evidently suggested considerable leaching of active
species in Pd-Fe3O4@NC catalyst took place (Table S2, SI). The Fe 2p XPS spectra peaks of
used catalyst noticed at the binding energies about 710.3 (Fe 2p3/2), 724.152 (Fe 2p1/2) along
with satellite peaks (Figure S7 ESI), and identical with fresh catalyst Fe 2p XPS spectra.
Moreover, the elemental surface composition of carbon noticed as 55.36 and 59.02 mol % for
used PdCo3O4@NC and PdFe3O4@NC catalysts, respectively, indicating that there is more
amount of carbon deposited on the surface of the used PdFe3O4@NC catalyst compared to
the used PdCo3O4@NC catalyst, and very poor signal detection noticed from used
PdFe3O4@NC catalyst. The obtained result from XPS analysis of fresh and used catalysts
suggested that the stability of active PdCo3O4@NC nanohybrid improved which could be
ascribed to the strong synergistic effect between Pd and Co3O4 compared with Pd and Fe3O4.
Moreover, we have noticed good results from reusability test up to fourth reaction run (Figure
10b) which furtherly confirmed the robust nature of PdCo3O4@NC nanohybrid. After
isolation of PdCo3O4@NC nanohybrid by centrifugation followed by washed with the
methanol and oven dried at 80ºC from the first run reaction mixture we have conducted four
more reaction runs at optimized reaction conditions and the yields of THFAL from furfural
obtained as 94, 92, 89 and 85% for second, third, fourth and fifth run, respectively, with
complete conversion, and this negligible decline in the yield of THFAL can be attributed to
minimal carbon deposition on the surface of the active sites which may furtherly lead to the
minimized porosity of nanohybrid.48,49 To have an insight into the surface and structural
changes, the used catalyst was characterized by N2 adsorption and desorption and TEM
analysis. To understand the structural change of reused catalysts we have analysed all the
spent catalysts after a fourth catalytic run by TEM analysis (Figure S8 ESI). TEM images of
20

Page 21 of 26
Dalton Transactions
reused PdCo3O4@NC indicating that the particle sizes increased with an average size rVaienwgAerticle Online
DOI: 10.1039/C9DT01190K
of 25 to 40 nm along with minimal carbon deposition on the surface of the active sites and
aggregation of the nanoparticles as well. But In the case of Pd-Fe3O4@NC a severe
aggregation of the nanoparticles has been noticed (Figure S8c ESI). The surface area of the
catalysts was slightly decreased compared to the fresh catalysts and the pore size of the
catalysts also decreased. This is may be due to the carbon deposition on the pores of the
catalyst after the reaction. The exhibited isotherm from used PdFe3O4@NC and
PdCo3O4@NC are corresponding to a type (II) with H3 hysteresis in the Brunauer
classification (Figure S9 ESI), and the surface area values for Pd-Fe3O4@NC and Pd-
Co3O4@NC was found to be 53 m2/g and 96 m2/g respectively.
Figure 10: XP spectra in Pd-3d region of the used PdCo3O4@NC and PdFe3O4@NC
catalysts (a), investigation of the stability of the catalyst. Experimental conditions: furfural (1
mmol), isopropanol (25 mL), 70 mg PdCo3O4@NC catalyst, H2 (20 bar), 6 h (b).
CONCLUSIONS:
In summary, present study describes the facile strategy to development of PdCo3O4
nanoparticles encapsulated in graphitic N-doped carbon matrix (PdCo3O4@NC), via
stabilized Pd nanoparticle (PVP-Pd) deposited on the ZIFs metal-organic framework (PVP-
Pd@ZIF-67) subsequently pyrolyzed in molecular hydrogen gas, for deep insight into
investigation and comparison with PdFe3O4@NC synergetic effects on catalytic activity. In
particular, PdCo3O4@NC nanohybrid with a composition of PdFe3O4@NC exhibited superior
21

Dalton Transactions
Page 22 of 26
View Article Online
catalytic activity toward the conversion of furfural 100% with an exclusive yield 95% for
DOI: 10.1039/C9DT01190K
hydrogenation product THFAL (Tetrahydrofurfuryl alcohol). The characterization techniques
including XPS (fresh and used catalysts), H2-TPR studies experimentally evidenced that the
presence of PdCo-Nx active sites and the multiple synergistic effects are responsible for the
superior catalytic activity and stability of PdCo3O4@NC nanohybrid.
ASSOCIATED CONTENT
†Electronic supplementary information (ESI) available: Characterization techniques, FE-
SEM images of PVP-Pd@ZIF-67, Wide angle powder XRD patterns and simulated pattern of
Co-ZIF, XRD patterns of Fe-ZIF, Pore-size distribution, & FE-SEM images of Pd-
Co3O4@NC, Pd-Fe3O4@NC, O-1s XPS spectra of PdCo3O4@NC and PdFe3O4@NC, Fe-2p
XP spectra of used Pd-Fe3O4@NC, HR-TEM images and N2 adsorption/desorption isotherms
of used Pd-Co3O4@NC, Pd-Fe3O4@NC, and Plausible mechanistic pathway.
AUTHOR INFORMATION
Corresponding Author
*E-mail: johncuchem@gmail.com; johnmondal@iict.res.in
ORCID
John Mondal: 0000-0001-7813-2108
Notes
The authors declare no competing financial interest
ACKNOWLEDGMENTS
The authors are grateful for the financial support by the Department of Science and
Technology, India, for DST-INSPIRE Faculty Research project grant (GAP-0522) at CSIR-
IICT, Hyderabad. P.S. wishes to thankfully acknowledge CSIR, New Delhi, for his respective
CSIR-UGC fellowship.
REFERENCES:
1. I. Ganguly, F. Pierobon, T. C. Bowers, M. Huisenga, G. Johnston and I. L. Eastin,
Biomass and Bioenergy., 2018, 108, 207-216.
22

Page 23 of 26
Dalton Transactions
View Article Online
DOI: 10.1039/C9DT01190K
2. K. Dutta, A. Daverey and J. G. Lin, Renew. Energy., 2014, 69, 114-122.
3. P. Champagne, Resour Conserv Recycl., 2007, 50, 211-230.
4. M. Alkasrawi, Z. Al-Hamamre, M. Al-Shannag, M. J. Abedin and E. Singsaas, Bio
Res., 2016, 11(1), 2287-2296.
5. C. Wang, J. D. Lee, Y. J. T. Ming Onn, J. Luo, C. B. Murray and R. J. Gorte, Catal
Letts., 2018, 148, 1047-1054.
6. K. Salnikova, V. Matveeva, A. Bykov, G. Demidenko, I. Shkileva and E. Sulman,
ChemEng Trans., 2018, 70, 379-384.
7. J. J. Musci, A. B. Merlo and M. L. Casella, Catal. Today., 2016, 296, 43-50.
8. C. Ramirez-Barria, M. Isaacs, K. Wilson, A. Guerrero-Ruiz and I. Rodríguez-Ramos,
Appl. Catal., A. 2018, 563, 177-184.
9. R. M. Mironenko, O. B. Belskaya, T.I, Gulyaeva, A. I. Nizovskii, A. V. Kalinkin, V.
I. Bukhtiyarov, A. V. Lavrenov and V. A. Likholobov, Catal. Today., 2015, 249,
145-152.
10. C. Wang, Y. V. Kaneti, Y. Bando, J. Lin, C. Liu, J. Li and Y. Yamauchi, Mater.
Horiz., 2018, 5, 394-407.
11. F. Yang, W. Li, Y. Zhanga and B. Tang, Dalton Trans., 2018, 47, 13657-13667.
12. Q. L. Zhua, P. Pachfulea, P. Strubelb, Z. Lia, R. Zouc, Z. Liud, S. Kaskelb and Q. Xu,
Energy Storage Materials., 2018, 13, 72-79.
13. W. Xuan, R. Ramachandran, C. Zhao and F. Wang, J Solid State Electrochem., 2018,
22, 3873-388.
14. D. Banerjee, C. M. Simon, S. K. Elsaidi, M. Haranczyk and P. K. Thallapally, Chem.,
2018, 4(3), 466-494.
15. L. Yang, X. Zeng, W. Wang and D. Cao, Adv. Funct. Mater., 2018, 28, 1704537.
16. A. Aijaz, N. Fujiwara and Q. Xu, J. Am. Chem. Soc., 2014, 136(19), 6790-6793.
17. H. Zhang, J. Li, Q. Tan, L. Lu, Z. Wang and G. Wu, Chem. Eur J., 2018, 24,
18137-18157.
18. Y. Zhan, L. Shen, C. Xu, W. Zhao, Y. Cao and L. Jiang, CrystEng Comm., 2018,
20(25), 3449-3454.
19. J. Zhou, Y. Dou, A. Zhou, L. Shu, Y. Chen and J. R. Li, ACS Energy Lett., 2018,
3(7), 1655-1661.
20. V. I. Isaeva, O. M. Nefedov and L. M. Kustov, Catalysts 2018, 8, 368.
21. P. Sudarsanam, R,. Zhong , S. V. Bosch, S. M. Coman , V. I. Parvulescu and B. F.
Sels, Chem Soc Rev., 2018, 47, 8349-8402.
23

Dalton Transactions
Page 24 of 26
View Article Online
DOI: 10.1039/C9DT01190K
22. L. Zhaoqiang and Y. Longwei, Energy Storage Materials., 2018, 14, 367-375.
23. R. Wang, X. Sun, S. O. Chikh, D. Osadchii, F. Bai, F. Kapteijn and J. Gascon, Appl.
Mater. Interfaces., 2018, 10 (17), 14751-14758.
24. C. Young, R. R. Salunkhe, J. Tang, C. C. Hu, M. Shahabuddin, E. Yanmaz, M.
Shahriar, A. Hossain, J. H. Kim and Y. Yamauchi, Phys. Chem. Chem. Phys., 2016,
18, 29308-29315.
25. Y. Su, C. Chen, X. Zhu, Y. Zhang, W. Gong, H. Zhang, H. Zhao and G. Wang,
Dalton Trans., 2017, 46, 6358-6365.
26. L. Wan, E. Shamsaei, C. D. Easton, D. Yu, Y. Liang, X. Chen, Z. Abbasi, A. Akbari,
X. Zhang and H. Wang, Carbon., 2018, 121, 330-336.
27. Y. Chen, G. Cai, Y. Wang, Q. Xu, S. Yu and H. Jiang, Green Chem., 2016, 18,
1212-1217.
28. X. Liu, B. Zhang, B. Fei, X. Chen, J. Zhanga and X. Mu, Faraday Discuss., 2017,
202, 79-98.
29. M. A. Tike and V. V. Mahajani, Ind. Eng. Chem. Res., 2007, 46, 3275-3282.
30. (a) K. Yang, P. Jiang, J. Chen and Q. Chen, ACS Appl. Mater. Interfaces., 2017, 9,
37, 32106-32113. (b)W. Dong, L. Zhang, C. Wang, C. Feng, N. Shang, S. Gao and C.
Wang, RSC Advances, 2016, 6(43), 37118–37123.
31. Y. Soloveva, Y. V. Ioni and S. P. Gubin, Mendeleev Commun., 2016, 26, 38-39.
32. J. Zhang, X. Wang, D. Qin, Z. Xue and X. Lu, Appl. Surf. Sci., 2014, 320, 73-82.
33. X. Wei, Y. Zhou, Y. Li and W. Shen, RSC Adv., 2015, 5, 66141-66146.
34. A. Sárkány, Z. Zsoldos, G. Stefler, J. W. Hightower and L. Guczi, J. Catal., 1995,
157, 179-189.
35. K. Shen, L. Chen, J. Long, W. Zhong and Y. Li, ACS Catal., 2015, 5, 5264-527.
36. G. Ma, C. Li, F. Liu, M. K. Majeed, Z. Feng, Y. Cui, J. Yang and Y. Qian, Materials
Today Energy., 2018, 10, 241-248.
37. M. Savastano, P. A. Mascarós, C. Bazzicalupi, M. P. Clares, M. L. G. Salido, M. D.
G. Valero, M. Inclán, A. Bianchi, E. G. España and R. L. Garzón, J. Catal., 2017,
353, 239-249.
38. Q. Qu, J. H. Zhang, J. Wang, Q. Y. Li, C. W. Xu and X. Lu, Sci Rep., 2017, 7, 41542.
39. M. A. Ghasemzadeh and Z. Elyasi, Iran. j. catal., 2017, 7(1), 75-83.
40. Y. Tuo, G. Liu, B. Dong, J. Zhou, A. Wang, J. Wang, R. Jin, H. Lv, Z. Dou and W.
Huang, Sci Rep., 2015, 5, 13515.
24

Page 25 of 26
Dalton Transactions
41. X. Zhang, Y. Niu, X. Meng, Y. Li and J. Zhao, CrystEngComm., 2013, 15, 8V1ie6w6Ar-ticle Online
DOI: 10.1039/C9DT01190K
8172.
42. K. Song, Y. Lee, M. R. Jo, K. M. Nam and Y. M. Kang, Nanotechnology., 2012, 23,
505401.
43. A. Diallo, A. C. Beye, T. B. Doyle, E. Park and M.Maaza, Green Chem Lett Rev.,
2015, 8(3-4), 30-36.
44. C. W. Tang, C. B. Wang and S. H. Chien, ThermochimicaActa., 2008, 473 (1-2), 68-
73.
45. S. H. Cho, J. W. Jung, C. Kim and I. D. Kim, Sci Rep., 2017, 7(1), 45105.
46. S. Bhogeswararao and D. Srinivas, J. Catal., 2015, 327, 65-77.
47. S. Sitthisa, T. Sooknoi, Y. Ma, P. B. Balbuena and D. E. Resasco, J. Catal., 2011,
277, 1-13.
48. M. D. Argyle and C. H. Bartholomew, Catalysts., 2015, 5, 145-269.
49. J. V.Doorn and J.A. Moulijn, Catal. Today., 1990, 7, 257-266.
25

Dalton Transactions
Page 26 of 26
View Article Online
DOI: 10.1039/C9DT01190K
Graphical Abstract:
Metal-Organic-Framework Derived Co-Pd Catalyst is Preferred over Fe-Pd for
Reductive Upgrading of Furfural to Tetrahydrofurfuryl alcohol
Saikiran Pendem, Bolla Srinivasa Rao, David J. Morgan, Digambar B. Shinde, ZhipingLai,
Nakka Lingaiah, and John Mondal*
Metal-Organic-Framework derived Co-Pd bond can efficiently catalyze reductive upgrading
of Furfural to Tetrahydrofurfuryl alcohol production than Fe-Pd bond.
26