Efficient photocatalytic one-pot hydrogenation and N-alkylation of nitrobenzenes/benzonitriles with alcohols over Pd/MOFs: Effect of the crystal morphology & “quasi-MOF” structure

Article abstract of DOI:10.1016/j.jcat.2020.05.033

One-pot multi-step reactions over visible-light induced catalysis feature the sustainable green process. Here, ligand structure change and 2-MI coordinated modulation were adapted to adjust the crystal size, morphology and crystalline structure of Fe-MOFs; double solvent impregnation was employed for the Pd loading; “quasi-MOF” materials with retained morphology were formed with calcination under N₂. Above modified materials were employed as multifunctional photocatalysts for highly efficient one-pot hydrogenation and N-alkylation of nitrobenzenes or benzonitriles with alcohols after in situ Pd photoreduction. Photocatalytic performance was evidently affected by the Fe-MOFs crystal size, morphology, crystalline structure alteration and “quasi-MOF” construction. One-pot hydrogenation and N-alkylation of benzonitriles with alcohols was achieved with excellent catalytic performance firstly in heteroegeneous catalysis. Reaction mechanism was proposed with the assistance of in situ DRIFTS.

Full text of DOI:10.1016/j.jcat.2020.05.033

Journal Pre-proofs
Efficient photocatalytic one-pot hydrogenation and N-alkylation of nitroben-
zenes/benzonitriles with alcohols over Pd/MOFs: effect of the crystal mor-
phology & “quasi-MOF” structure
Hongmei Cheng, Xingyu Long, Fengxia Bian, Chaofen Yang, Xingyan Liu,
Heyan Jiang
PII:
S0021-9517(20)30214-1
https://doi.org/10.1016/j.jcat.2020.05.033
YJCAT 13763
DOI:
Reference:
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Journal of Catalysis
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25 April 2020
22 May 2020
Please cite this article as: H. Cheng, X. Long, F. Bian, C. Yang, X. Liu, H. Jiang, Efficient photocatalytic one-pot
hydrogenation and N-alkylation of nitrobenzenes/benzonitriles with alcohols over Pd/MOFs: effect of the crystal
morphology & “quasi-MOF” structure, Journal of Catalysis (2020), doi: https://doi.org/10.1016/j.jcat.
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Efficient photocatalytic one-pot hydrogenation and N-alkylation
of nitrobenzenes/benzonitriles with alcohols over Pd/MOFs:
effect of the crystal morphology & "quasi-MOF" structure
[a]
[a]
[a]
[b]
[a]
Hongmei Cheng, Xingyu Long, Fengxia Bian, Chaofen Yang, Xingyan Liu,
Heyan Jiang *[a]
[a] Key Laboratory of Catalysis Science and Technology of Chongqing Education
Commission, Chongqing Key Laboratory of Catalysis and New Environmental
Materials, College of Environmental and Resources, Chongqing Technology and
Business University, Chongqing 400067, China. * Corresponding author. E-mail:
orgjiang@163.com.
[b] Research Center for Analysis and Measurement, Kunming University of Science
and Technology, Kunming 650093，China.
Abstract
One-pot multi-step reactions over visible-light induced catalysis feature the sustainable green
process. Here, ligand structure change and 2-MI coordinated modulation were adapted to adjust
the crystal size, morphology and crystalline structure of Fe-MOFs; double solvent impregnation
was employed for the Pd loading; "quasi-MOF" materials with retained morphology were formed
with calcination under N . Above modified materials were employed as multifunctional
2
photocatalysts for highly efficient one-pot hydrogenation and N-alkylation of nitrobenzenes or
benzonitriles with alcohols after in situ Pd photoreduction. Photocatalytic performance was
evidently affected by the Fe-MOFs crystal size, morphology, crystalline structure alteration and
"quasi-MOF" construction. One-pot hydrogenation and N-alkylation of benzonitriles with alcohols
was achieved with excellent catalytic performance firstly in heteroegeneous catalysis. Reaction
mechanism was proposed with the assistance of in situ DRIFTS.
Keywords: Photocatalysis, Pd/quasi-MOF, N-Alkylation, Nitrobenzenes, Benzonitriles.
1
. Introduction
N-alkylation products have been widely used in many important fields including pesticides,
medicines as well as bioactive molecules [1]. Till now, addition, cycloaddition as well as cross
coupling methods have been developed to synthesize such intermediates [2-4]. As a very
important branch research in the field of green chemistry, one-pot multi-step reaction is not only

beneficial to avoid intermediates isolating and purifying, but also favorable to improve the atomic
economy in practical applications [5-7]. So, different approaches have been explored to avoid
harsh reaction conditions, poor atomic economics as well as difficulties in isolating and purifying
intermediates in traditional N-alkylation intermediates preparation. Jiang et al. [8] used the
multifunctional catalyst PdAg@MIL-101(Cr) to realize a one-pot three-step reaction, which could
directly convert nitrobenzene and benzaldehyde to N-benzoaniline in the presence of 2 bar H2.
Using light to drive one-pot multi-step organic transformations under mild conditions is very
attractive. Li et al. [9-13] found that N-alkyl amines could be prepared from alcohols and amines
with excellent catalytic performance over MIL-100(Fe) or ZnIn S loaded Pd nanoparticles with
2
4
visible light. The N-alkylation of alcohol with amine followed a hydrogen self-transfer mechanism
consisting of three continuous catalytic steps.
To achieve one-pot multi-step reaction in a single pot, multifunctional catalyst with different
catalytically active sites is typically required to maintain its independent function. Metal organic
frameworks (MOFs) have the advantages of diverse highly ordered porous crystalline structure,
large specific surface area, easy synthesis and modification as well as good thermal stability and
chemical stability [14]. Therefore, MOFs have a broad application prospect in multifunctional
catalysis [15]. It is of special interest that catalytic performance could be significantly influenced
with the adjustment of the MOFs crystal size, morphology as well as crystalline structure through
affect the diffusion pathway of transport guest molecules and active sites exposure in nanocrystal
structure [16-18]. Moreover, crystal size, morphology as well as crystalline structure adjustment in
MOFs could significantly affect visible light absorption, charge separation efficiency along with
charge directional transmission. Commonly used strategies for the crystal size, morphology and
crystalline structure adjustment in MOFs mainly include ligand structure and central metal
variation [19-21], additive introduction during MOFs synthesis through coordinated modulation
strategy [22,23], and chemical etching after MOFs synthesis [24-26].
Metal nanoparticles (NPs)/MOF nanocomposites strategy was commonly applied to
light-induced reactions in recent years [27-31]. However, the inorganic nodes in the metal
NPs/MOF structure were isolated by coordinated ligands, which weakened the interaction between
inorganic nodes and metal NPs [32]. In addition to introducing bridged moieties to improve the
interaction, many strategies, such as calcination in air or inert gas to remove the organic ligands
[33], have also been developed to improve the interaction between metal NPs and inorganic nodes.
Recently, Tsumori et al. [34] addressed the metal/MOF composites controlled deligandation
through heat treatment to obtain "quasi-MOF", which enhanced the interaction between Au
nanoparticles and Cr3+ nodes with retained MOF porous structure. And the catalytic carbon
monoxide oxidation performance was obviously improved.
In this study, crystal size, morphology along with crystalline structure adjustment in
MIL-101(Fe) was firstly conducted with strategies of ligand structure variation and
2
-methylimidazole (2-MI) coordinated modulation. Then Pd nanoparticles embedded in various
Fe-MOFs (MIL-101(Fe), NH -MIL-101(Fe), MIL-101(Fe)-2MI, NH -MIL-101(Fe)-2MI etc.)
2
2
cavities were prepared by double solvent impregnation method. Thirdly, "quasi-MOF" materials
Pd/MIL-101(Fe)-2MI(300), Pd/NH -MIL-101(Fe)-2MI(300), and 300 represented the calcination
(
2
temperature) were formed through Pd/NH -MIL-101(Fe) MOFs calcination under nitrogen. With
2
in situ photoreduction of Pd, above obtained materials were employed for highly efficient
photoinduced one-pot hydrogenation and N-alkylation of a broad range of nitrobenzenes or

benzonitriles with alcohols. It is worth mentioning that one-pot hydrogenation and N-alkylation of
benzonitriles with alcohols was achieved with excellent catalytic performance for the first time
with heteroegeneous catalysis. Accompany with the crystal size, morphology, crystalline structure
adjustment and "quasi-MOF" introduction, both photocatalytic activity and chemoselectivity in
these four continuous catalytic step reactions was obviously influenced. Such as, in comparison
with Pd/NH -MIL-101(Fe), 2-MI assisted needle-like Pd/NH -MIL-101(Fe)-2MI improved the
2
2
nitrobenzene conversion from 82% to 100%, and N-alkylation chemoselectivity was promoted
from 64% to 86%; with strong interaction formed between Pd NPs and inorganic nodes in
"
quasi-MOF" (Pd/NH -MIL-101(Fe)-2MI(300)), N-alkylation chemoselectivity promotion from
2
8
6% to 96% was achieved. In addition, the reaction mechanism was proposed with in situ diffuse
reflection infrared Fourier transform spectroscopy (DRIFTS). This investigation not only
demonstrated an efficient way to realize N-alkyl amines from nitrobenzenes or benzonitriles and
alcohols, but also emphasized the broad application prospect of multifunctional catalysis for the
organic compounds preparation in a one-pot multi-step reaction induced by visible light.
2
. Results and discussion
Figure 1. The SEM images of (a) MIL-101(Fe); (b) NH
2
-MIL-101(Fe); (c) MIL-101(Fe)-2MI; (d)
-MIL-101(Fe)-2MI(300).
NH -MIL-101(Fe)-2MI; (e) NH -MIL-101(Fe)-2MI(300). TEM of (f) Pd/NH
2
2
2

MOFs have the characteristics of structure flexibility and function adjustable, which provide
opportunity to change their size, morphology and crystalline structure. We prepared a series of
Fe-MOFs materials, and tried to inspect the relationship between the size, morphology along with
crystalline structure change and the photocatalytic performance. The size and morphology of
Fe-MOFs was characterized with scanning electron microscopy (SEM). Identical to the classical
solvothermally synthesized crystal morphology [35,36], MIL-101(Fe) crystal had a typical
octahedral morphology with the size of approximately 7 μm, and NH -MIL-101(Fe) had an
2
irregular polygonal structure with the size of about 3 μm (Figure 1a and 1b). To adjust the size as
well as morphology of MIL-101(Fe) and NH -MIL-101(Fe), 2-MI was introduced as a modulator
2
during the MIL-101(Fe)-2MI and NH -MIL-101(Fe)-2MI synthesis [23]. Uniform shape of
2
grain-like MIL-101(Fe) and needle-like NH -MIL-101(Fe) were obtained with 2-MI assistance
2
(
Figure 1c and 1d). The size of MIL-101(Fe) as well as NH -MIL-101(Fe) crystals was around 11
2
μm and 14 μm, respectively. 2MI could accelerate the deprotonation rate of the carboxyl linker
and promote the coordination of the ligand with the metal ion; which result in the formation and
growth of different crystal nuclei, change of the crystal size as well as morphology, and increase
the crystallinity. As an emerging material, "quasi-MOF" can not only maintain the porosity of the
framework to a certain extent, but also promote the interaction between metal NPs and inorganic
nodes [34], and the strong interaction might have special influence on the catalytic performance.
o
Therefore, "quasi-MOF" (Pd/NH -MIL-101(Fe)-2MI(300)) was prepared by 300 C calcining
2
under N for 30 min [34,37]. Original size and morphology was maintained during the
2
"quasi-MOF" preparation (Figure 1e). The HRTEM images revealed that Pd NPs were well
dispersed on NH -MIL-101(Fe)-2MI(300) (Figure 1f). The 0.236 nm lattice fringe matched the Pd
2
(111) face-centered cubic plane (inset in Figure 1f), and the average particle size of Pd NPs was
about 4.7 nm (Figure S1 in SI). Energy-dispersive X-ray (EDX) spectra of
Pd/NH -MIL-101(Fe)-2MI(300) showed the presence of Fe, C, O, N and Pd elements in
2
Pd/NH -MIL-101(Fe)-2MI(300) (Figure S2b in SI). Corresponding mapping images showed that
2
Pd was well distributed on NH -MIL-101(Fe)-2MI support (Figure S2a in SI).
2
2
Figure 2. The XRD patterns of (a) MIL-101(Fe); (b) NH -MIL-101(Fe).
X-ray diffraction (XRD) is the most commonly used method to study the crystal structure and
crystallinity of materials. Therefore, XRD was used to analyze the change of Fe-MOFs materials
in the process of size and morphology change as well as "quasi-MOF" structure formation.
According to the XRD pattern (Figure 2), the MIL-101(Fe) and NH -MIL-101(Fe) XRD peaks
2

were consistent with literature [23,35,38]. In addition, the XRD diffraction pattern of
MIL-101(Fe)-2MI and NH -MIL-101(Fe)-2MI synthesized with the assistance of 2-MI well
2
matched the diffraction pattern of traditional MIL-101(Fe) and NH -MIL-101(Fe), which
2
indicated that MIL-101(Fe) and NH -MIL-101(Fe) coordination mode was not affected by 2-MI
2
introduction and high pure 2-MI modified MIL-101(Fe)-2MI and NH -MIL-101(Fe)-2MI were
2
obtained [17,23]. On the other hand, MIL-101(Fe)-2MI and NH -MIL-101(Fe)-2MI displayed
2
stronger diffraction peak intensity than MIL-101(Fe) and NH -MIL-101(Fe) owing to the
2
crystallinity increase. After Pd loading, the XRD pattern of Pd/MIL-101(Fe)-2MI and
Pd/NH -MIL-101(Fe)-2MI were similar to parental MIL-101(Fe) and NH -MIL-101(Fe), no
2
2
obvious Pd diffraction was detected, which should be related to small loading as well as well
dispersion. Similar to previous report [34], the diffraction peak of "quasi-MOF"
Pd/NH -MIL-101(Fe)-2MI(300) widened at about 5°-10°, the other diffraction peaks were
2
basically consistent with NH -MIL-101(Fe)-2MI. Obviously, NH -MIL-101(Fe)-2MI maintained
2
2
a certain framework structure during the calcination. The diffraction peak intensity decrease in
Pd/NH -MIL-101(Fe)-2MI(300) should be owing to the MOF crystal structure partly destruction
2
o
caused by calcining at 300 C [39]. Such decomposition should be beneficial to enhance the
interaction between inorganic nodes and Pd NPs [34]. The Brunauer-Emmett-Teller (BET) surface
areas of as-synthesized NH -MIL-101(Fe), NH -MIL-101(Fe)-2MI, Pd/NH -MIL-101(Fe)-2MI
2
2
2
2
-1
and Pd/NH -MIL-101(Fe)-2MI(300) were 994.0, 1193.3, 663.8 and 215.5 m ·g , respectively
2
(Table S1 in SI). The morphology adjustment with 2-MI increased the specific surface area and
pore volume; after Pd NPs loading, the specific surface area and pore volume obviously
decreased, implying that the cavities of the host framework were occupied by highly dispersed Pd
NPs. Due to the partial organic linker decomposition and/or collapse in
Pd/NH -MIL-101(Fe)-2MI(300) preparation, further decrease in the surface area and pore volume
2
was detected.

Figure
3.
-MIL-101(Fe)-2MI and Pd/NH
-MIL-101(Fe)-2MI(300) and Pd/NH
-MIL-101(Fe)-2MI and Pd/NH -MIL-101(Fe)-2MI(300).
(a)
FTIR
spectra
of
-MIL-101(Fe)-2MI(300). (b) Raman spectra for Pd/NH
-MIL-101(Fe)-2MI. XPS spectra of Fe 2p (c) and Pd 3d (d) of
MIL-101(Fe),
NH
2
-MIL-101(Fe),
NH
2
-MIL-101(Fe)-2MI,
Pd/NH
Pd/NH
Pd/NH
2
2
2
-MIL-101(Fe),
2
2
2
2
Fourier transform infrared (FTIR), Raman, and X-ray photoelectron spectroscopy (XPS)
were employed to study internal structural change during morphology regulation and
"
quasi-MOF" synthesis. FTIR spectrum of NH -MIL-101(Fe)-2MI and Pd/NH -MIL-101(Fe)-2MI
2
2
-1
were similar to NH -MIL-101(Fe) (Figure 3a). Strong bands in 1583 and 1384 cm region were
2
attributed to symmetric and asymmetric telescopic vibration of skeleton O-C-O in MIL-101(Fe)
[
40]. The peak at 553 cm-1 in MIL-101(Fe) and 523 cm-1 in NH -MIL-101(Fe) were Fe-O
2
-1
vibration, and the peak at 1497 cm was related to C=C vibration in aromatic ring [41]. The 1626
-1
and 1262 cm bands were attributed to N-H stretching vibration and C-N deformation vibration
42]. The absorption at 1675 cm-1 in NH -MIL-101(Fe)-2MI should be the C=N stretching
[
2
vibration from 2-MI [43]. Above results illustrated that there had no obvious change in the crystal
coordination mode after size and morphology regulation, but some 2-MI may exist in
-1
NH -MIL-101(Fe)-2MI. After Pd NPs loading, the peak at 1626 cm decreased with a tendency to
2
broaden, indicating Pd NPs should be coordinated with amino groups. For
-1
Pd/NH -MIL-101(Fe)-2MI(300), 1583 and 1384 cm peaks from 2-aminoterephthalate ligand in
2
NH -MIL-101(Fe) became broaden accompany with two peaks distance decrease [23], which
2
further evidenced the partially decompose of the organic ligand in NH -MIL-101(Fe).
2
Additionally, the peak belonging to the C=N bond from 2-MI disappeared in
Pd/NH -MIL-101(Fe)-2MI(300) FTIR spectra, indicating 2-MI had been decomposed during the
2
"quasi-MOF" preparation.
The observation in Raman spectrum (Figure 3b) was in agreement with the FTIR result. In
Pd/NH -MIL-101(Fe), the band at 1627 cm was the C-O stretching, 1454 cm-1 was the
-1
2
out-of-phase stretching vibration of carboxylate group. The band at 1272 cm-1 was the
-1
deformation vibration of the carboxylate group. Three bands at 860, 690 and 630 cm were C-C
telescopic vibration and C-H stretching vibration [44-46]. The 1350 cm-1 in
Pd/NH -MIL-101(Fe)-2MI should be the deformation vibration of C=N bond from 2-MI [47,48].
2
Peaks at 1400-1700 cm-1 were assigned to characteristic peaks of 2-aminoterephthalate ligand
-1
from NH -MIL-101(Fe)-2MI. For Pd/NH -MIL-101(Fe)-2MI(300), peaks around 1400-1700 cm
2
2
became broaden and decreased in intensity after the decomposition of NH -MIL-101(Fe)-2MI
2
structure during the "quasi-MOF" preparation.
XPS was used to check the chemical valence of Fe and Pd in the catalysts and the change in
binding energy during the formation of a "quasi-MOF" structure (Figures 3c, 3d, and Figure S4 in
SI). The XPS of Fe 2p in Pd/NH -MIL-101(Fe)-2MI showed two peaks at 711.3 and 724.8 eV,
2
which were Fe 2p3/2 and Fe 2p1/2 from Fe(III), respectively. The 716.7 eV satellite peak should
also be owing to Fe(III) in Figures 3c [49]. In Pd/NH -MIL-101(Fe)-2MI(300), Fe 2p3/2 and Fe
2
2
p1/2 were at 711.5 and 725.0 eV, which indicated that partial decomposition of
NH -MIL-101(Fe)-2MI framework changed the coordination environment of Fe and increased its
2
0
binding energy. Pd/NH -MIL-101(Fe)-2MI had two peaks at 335.0 and 340.2 eV assigning to Pd
2
0
3
d5/2 and Pd 3d3/2, which demonstrated the existence of Pd NPs in the sample (Figures 3d) [50].
0
0
On the other hand, the two peaks of Pd 3d5/2 and Pd 3d3/2 in Pd/NH -MIL-101(Fe)-2MI(300)
2

moved to higher binding energy (335.2 and 340.4 eV (Figures 3d) when compared to the
0
0
Pd/NH -MIL-101(Fe)-2MI. The increase in Pd 3d5/2 and Pd 3d3/2 binding energy should be
2
caused by the strong interaction between Pd NPs and inorganic nodes.
2 2
Figure 4. TGA of Pd/NH -MIL-101(Fe) and Pd/NH -MIL-101(Fe)-2MI.
To further confirm the presence of 2-MI in the crystal structure, thermogravimetric analysis
TGA) was performed with Pd/NH -MIL-101(Fe) and Pd/NH -MIL-101(Fe)-2MI. TGA results
(
(
2
2
Figure 4) show that Pd/NH -MIL-101(Fe) and Pd/NH -MIL-101(Fe)-2MI had almost the same
2
2
o
thermal behavior. The crystal structure decomposed above 300 C, and the thermal stability of
Pd/NH -MIL-101(Fe) was slightly lower than Pd/NH -MIL-101(Fe)-2MI, possibly due to the low
2
2
crystallinity in Pd/NH -MIL-101(Fe). The first stage weight loss before 150 °C was the release of
2
solvent molecule (e.g. H O and methanol) adsorbed on NH -MIL-101(Fe) and
2
2
NH -MIL-101(Fe)-2MI surface [51], weight loss was 7.4%. The second stage weight loss was
2
between 150 and 300 °C, weight loss was 10.7%, which should be the further release of DMF in
the pores and the elimination of OH, Cl groups [52], and there was no significant difference in the
weight loss of the two crystals at this stage. The third stage weight loss of Pd/NH -MIL-101(Fe)
2
after 300 °C was about 42.9% (molecular formula of NH -MIL-101(Fe) is C H ClO N Fe , and
2
24 15
13
3
3
the theoretically loss in the third stage should be 44.2%), corresponding to the completely
decomposition of 2-aminoterephthalate ligand, and the main residual product was Fe O [53]. The
2
3
third weight loss for Pd/NH -MIL-101(Fe)-2MI was about 48.4%. Considering 2-MI would be
2
completely decomposed at about 200 °C, the Pd/NH -MIL-101(Fe)-2MI thermal stability
2
improvement above 300 °C should be explained that the existence of 2-MI in NH -MIL-101(Fe)
2
channel was beneficial for the overall framework structure stability.

2
Figure 5. (a) UV-Vis diffuse reflectance spectra, (b) Plots of (Ahν) vs photon energy.
The photocatalytic performance is largely depend on the light absorbing ability and the
charge carrier separation efficiency, so the light absorbing ability of the catalyst were investigated
with UV-Vis diffuse reflectance spectra (DRS). All materials had visible region absorption in
UV-vis DRS (Figure 5a) indicating the photocatalysis feasibility. It could be seen from the
diagram that the absorption of NH -MIL-101(Fe) in visible light region was stronger than
2
MIL-101(Fe), which illustrated the functionalization of amino group in ligand not only regulated
the particle size and morphology of MIL-101(Fe) but also greatly enhanced the NH -MIL-101(Fe)
2
absorption in the visible region. Strongest absorption band was observed around 350 nm for
Fe-MOFs, which was induced by “π-π” transitions between ligands [54]. The
NH -MIL-101(Fe)-2MI absorption enhancement accompanied with the crystal morphology
2
change and the crystallinity increase in visible light region should be beneficial to the Fe -µ -oxo
3
3
clusters excitation [55]. It was also found that Pd/NH -MIL-101(Fe)-2MI(300) could improve
2
light absorption in compared with Pd/NH -MIL-101(Fe)-2MI, but the light absorption in the
2
5
00-600 nm was slightly decreased. This decrease should be caused by the partial decomposition
in the 2-aminoterephthalate ligand, which reduced the absorption of the ligand in this region [54].
2
The band gap could be estimated from the Tauc plots of (Ahυ) vs photon energy (Figure 5b).
Fe-MOFs band gaps were around 2.76, 2.57 and 2.57, 2.39, 2.22 eV for MIL-101(Fe),
NH -MIL-101(Fe),
NH -MIL-101(Fe)-2MI,
Pd/NH -MIL-101(Fe)-2MI
and
2
2
2
Pd/NH -MIL-101(Fe)-2MI(300), respectively. It is worth noting that the addition of 2-MI had no
2
obvious effect on the NH -MIL-101(Fe) band gap as well as light absorption and utilization
2
ability. On the other hand, the amine group in ligand, Pd NPs loading and "quasi-MOF"
construction had obvious influence on the band gap and light absorption and utilization ability of
Fe-MOFs.

Figure 6. (a) Photocurrent responses, and (b) EIS Nyquist plots for MIL-101(Fe), MIL-101(Fe)-2MI,
NH -MIL-101(Fe)-2MI, NH -MIL-101(Fe)-2MI(300) and Pd/NH -MIL-101(Fe)-2MI(300).
2
2
2
Photocurrent measurements were employed to determine photogenerated charge separation
efficiency, where higher photocurrent usually associated with better photocatalytic performance
56]. The photocurrent response curves (Figure 6a) showed that the introduction of amino and
MI, the formation of "quasi-MOF" structure, and the loading of Pd NPs were all conducive to the
[
2
improvement of photocurrent. The study found that Pd/NH -MIL-101(Fe)-2MI(300) had the
2
highest charge separation efficiency. Electrochemical impedance spectroscopy (EIS) was utilized
to identify the carrier mobility (Figure 6b). EIS results demonstrated that
Pd/NH -MIL-101(Fe)-2MI(300) had the smallest radius, which meant the lowest charge transfer
2
resistance and the highest charge transfer efficiency. At the same time, the introduction of amino
group, 2-MI, and the formation of "quasi-MOF" structure were conducive to charge transfer. In
short, Pd/NH -MIL-101(Fe)-2MI(300) displayed brilliant photoresponsive properties, which
2
should be related to unique structure, matched band gap, efficient charge separation along with
electron transfer.
Table 1. Light-induced one-pot hydrogenation and N-alkylation of nitrobenzene with benzyl
alcohol over Pd/Fe-MOFs.
1
a
Sel. /%
Aldehyde
Entry Catalyst
Base
Conv. /%
3a
7
4a
85
-
BA
/μmol
1
Pd/MIL-101(Fe)-2MI
K PO
3
100
-a
8
-
174
-
4
4
4
4
2
MIL-101(Fe)-2MI
-
K PO
3
-
3b
4c
5
K PO
3
-
-
-
-
-
Pd/MIL-101(Fe)-2MI
Pd/MIL-101(Fe)-2MI
Pd/MIL-101(Fe)-2MI
Pd/MIL-101(Fe)-2MI
K PO
3
-
-
-
-
-
-
-
-
-
-
40
169
244
6d
K PO
3
100
74
10
71
85
29
5
-
4
7
KOH

8
9
1
1
1
1
1
1
1
1
1
Pd/MIL-101(Fe)-2MI
Pd/MIL-101(Fe)-2MI
Pd/MIL-101(Fe)-2MI
Pd/MIL-101(Fe)-2MI
Pd/MIL-101(Fe)
K CO
92
30
13
12
10
34
23
22
16
4
75
80
80
66
51
50
64
86
91
96
83
12
8
241
202
191
293
210
213
198
166
146
139
153
2
3
K HPO
2
4
0
1
2
3e
4
5
6
7
8
KHCO3
86
10
-
Et N
3
29
K PO
73
26
28
20
10
3
3
4
4
4
4
4
4
4
Pd/MIL-101(Fe)
K PO
3
72
Pd/NH -MIL-101(Fe)
K PO
3
82
2
Pd/NH -MIL-101(Fe)-2MI
K PO
3
100
100
100
94
2
Pd/MIL-101(Fe)-2MI(300)
K PO
3
5
Pd/NH -MIL-101(Fe)-2MI(300) K PO
4
-
2
3
Pd/NH -MIL-101(Fe)-2MI(350) K PO
11
1
2
3
Reaction conditions unless otherwise noted: 1a (0.1 mmol), 2a (3 mmol), 0.1 mmol% catalyst (based on Pd), base
additive (0.2 mmol), CH CN (2 mL), N
, 0.75 W cm-2 blue LED, irradiated for 24 h, conversion and
chemoselectivity were analyzed by GC and GC-MS. a “-” referred to no products or negligible products were
3
2
detected. No catalyst. Without light irradiation, 80 C. NaBH
4
reduced Pd. e Add the 2-MI(0.02 mmol).
b
c
o
d
N-alkylamines have broad application prospects in the synthesis of fine chemicals,
pharmaceuticals and agrochemicals [1]. In most catalytic studies, N-alkylamines were synthesized
through halobenzenes and benzylamines [57-59]. Interestingly, anilines and alcohols were
employed for N-alkylamines synthesis under visible light in recent years [9-13]. However, the use
of more challenging starting materials like nitrobenzenes or benzonitriles for the clean one-pot,
multi-step and highly chemoselectivie N-alkylamines synthesis is still rather attractive and
challenging. In table 1, the as-prepared Pd/Fe-MOF nanocomposites were employed to catalyze
N-alkylation reactions with nitrobenzene (1a) and benzyl alcohol (2a) with visible light in
CH CN. Reaction was initially carried out with the Pd/MIL-101(Fe)-2MI nanocomposite as the
3
photocatalyst and K PO as the base additive. Nitrobenzene was completely converted in 24 h,
3
4
with 85% chemoselectivity to N-benzylaniline (4a). N-benzylideneaniline (3a) and aniline (BA)
were the byproducts (Table 1, entry 1). The combination of Pd with MIL-101(Fe)-2MI was
necessary, no catalyst or just MIL-101(Fe)-2MI as the catalyst had no photocatalytic activity
(Table 1, entries 2-3). In the absence of visible-light, no nitrobenzene conversion was detected
o
with 80 C for 24 h, which indicated that catalytic activity was induced by visible-light (Table 1,
entry 4). Base additives were reported to have promotion effect on the catalytic hydrogenation and
dehydrogenation [60,61], similar phenomenon was observed in our photocatalytic system and
nitrobenzene hydrogenation could not be initiated in the absence of K PO (Table 1, entry 5). For
3
4
comparison, the Pd/MIL-101-2MI prepared by NaBH4 reduction was also used as the
photocatalyst in the one-pot hydrogenation and N-alkylation, and both the conversion of
nitrobenzene and the chemoselectivity to N-benzylaniline (4a) were nearly identical to
Pd/MIL-101(Fe)-2MI prepared by photoreduction (Table 1, entries 1 vs 6). The results indicated
that the Pd NPs should reasonably be the catalytic center during the photocatalytic
N-benzylaniline. In short, above results indicated the N-alkylation of nitrobenzene with benzyl
alcohol over Pd/MIL-101(Fe)-2MI nanocomposites was truly visible light induced photocatalysis,
while base additive introduction was an essential factor.
In order to clarify the effect of base, N-alkylation reaction was carried out with K PO , KOH,
3
4
K CO , K HPO , KHCO and Et N base additives (Table 1, entries 7-11). K PO was found to be
2
3
2
4
3
3
3
4

the best base additive. It was obvious that base additive K PO played the key role in the
3
4
nitrobenzene photocatalytic hydrogenation initiation (Table 1, entries 1 vs 5). Considering the role
of base additives on heterogeneous photocatalytic organic reactions was rarely studied, some other
experiment was carried out to clarify the effect of the base additive. Such as, when aniline was
used to replace nitrobenzene without or with base additive K PO under the same reaction
3
4
conditions for 12 h, the conversion of aniline was increased from 39% to 60% accompany with the
a chemoselectivity increase from 36% to 82% (Table S2 in SI). As we all know, the formation of
4
imine from benzaldehyde and aniline is very fast, therefore, the improvement of aniline
conversion indicated that base additive K PO had a significant promotion effect on the benzyl
3
4
alcohol oxidation to benzaldehyde. The increase in 4a chemoselectivity indicated that the base
additive K PO also accelerated the C=N group hydrogenation. Effect of light color on the
3
4
catalytic performance was further investigated. Pd/MIL-101(Fe)-2MI was utilized as the
photocatalyst to test one-pot hydrogenation and N-alkylation reaction with different lights
-2
including white, blue, green, cyan and red LED (0.75 W cm ), respectively. The influence of the
light source on the nitrobenzene conversion and the 4a chemoselectivity was obvious, and the blue
LED was the best light source (Figure 7). 450-600 nm light absorption should be related to the
3
+
excitation of Fe -µ -oxo clusters in the MIL-101(Fe) frame, which belonged to the Fe d-d
3
3
transition [62]. The blue LED wavelength was 460-465 nm, and Fe -µ -oxo clusters could be
3
3
excited more easily under this blue light radiation.
2
Figure 7. Pd/NH -MIL-101(Fe)-2MI photocatalyzed one-pot hydrogenation and N-alkylation of nitrobenzene with
benzyl alcohol under different light sources.
The morphology and crystallinity change in MOF materials would affect the charge
separation, charge transport along with photocatalytic performance [63,64]. In this study, we
modified the morphology and crystallinity characteristics of Fe-MOFs by introducing the amino
group in the organic linker ligand or applying 2-MI coordination modulator during the growth of
Fe-MOF. The relationship between morphology along with crystallinity of Fe-MOFs and one-pot
hydrogenation and N-alkylation catalytic reaction performance was evaluated with Pd/Fe-MOFs
as the catalyst. Only 73% nitrobenzene was hydrogenated with 51% chemoselectivity to 4a over
Pd/MIL-101(Fe) catalyst (Table 1, entry 12). This result indicated that the introduction of 2-MI in
the material synthesis process not only adjusted the morphology and crystallinity of the material,
but also improved the photocatalytic activity and chemoselectivity (Table 1, entries 1 vs 12). In
order to clarify whether the photocatalytic performance improvement was owing to the presence
of 2-MI or not, an appropriate amount of 2-MI was introduced to the Pd/MIL-101(Fe) catalyzed

reaction and almost no change in photocatalytic performance was observed (Table 1, entries 12 vs
3), which suggested the improvement of catalytic capability should be caused by the morphology
and crystallinity change. With the amino group introduced in the organic linker ligand and the
-MI added to assist NH -MIL-101(Fe)-2MI synthesis, further catalytic performance improvement
1
2
2
was observed with the Pd/NH -MIL-101(Fe)-2MI morphology and crystallinity change (Table 1,
2
entries 14-15). Compared with the 82% conversion and 64% chemoselectivity to 4a with
Pd/NH -MIL-101(Fe), the conversion of nitrobenzene could reach 100% with 86%
2
chemoselectivity to 4a over Pd/NH -MIL-101(Fe)-2MI (Table 1, entry 15). The catalytic
2
performance improvement with the amino group in organic linker ligand should be ascribed to the
improved metal stabilization and dispersion in the presence of amino group along with the
elevated light absorption ability accompany with the morphology change (Table 1, entries 12 vs
1
4 and entries 1 vs 15). Furthermore, the catalytic property optimization with the 2-MI addition
should be reasonably related to the light absorption enhancement accompany with crystallinity and
morphology adjustment (Table 1, entries 1 vs 12 and entries 14 vs 15). It was reported that
"quasi-MOF" could promote the interaction between metal NPs and inorganic nodes, and the
influence of "quasi-MOF" structure on photocatalytic performance was further investigated. After
the "quasi-MOF" treatment, 100% conversion and 91% chemoselectivity to 4a was attained with
Pd/MIL-101(Fe)-2MI(300) with nitrobenzene and benzyl alcohol (Table 1, entry 16), in addition,
up to 96% chemoselectivity to 4a was achieved with completely conversion over "quasi-MOF"
based material Pd/NH -MIL-101(Fe)-2MI(300) (Table 1, entry 17). In combination with XPS,
2
above catalytic result indicated that the strong interaction between metal Pd and inorganic nodes
was successfully formed with the partially remove of the organic ligand to fabricate "quasi-MOF"
and this strong interaction was favorable to the one-pot hydrogenation and N-alkylation catalytic
performance promotion. Further increase the material calcination temperature,
Pd/NH -MIL-101(Fe)-2MI(350) showed 94% conversion with 83% chemoselectivity to 4a (Table
2
1
, entry 18). The catalytic activity decrease should be owing to the serious decomposition of the
MOF structure, which was also observed in TGA. In addition, the stability of the catalyst was
determined with Pd/NH -MIL-101(Fe)-2MI(300) in light-induced one-pot hydrogenation and
2
N-alkylation reaction. Pd/NH -MIL-101(Fe)-2MI(300) showed high stability and recyclability,
2
and no catalytic activity and chemoselectivity loss was detected in five cycling tests (Figure 8),
and the XRD pattern of the catalyst is similar before and after five tests (Figure S5 in SI).

2
Figure 8. Cycling of Pd/NH -MIL-101(Fe)-2MI(300) for the one-pot hydrogenation and N-alkylation of
nitrobenzene with benzyl alcohol under visible light irradiation.
The one-pot hydrogenation and N-alkylation of nitrobenzenes with alcohols to generate
N-alkylated amines over Pd/NH -MIL-101(Fe)-2MI(300) nanocomposite was also explored in
2
Table 2. Different substituted nitrobenzenes and alcohols could be converted to N-alkyl anilines
with good to excellent activity and chemoselectivity. Nitrobenzenes with electron-withdrawing
substituents exhibited significantly conversion decrease (Table 2, entries 2-7). For contrast, the
conversion for nitrobenzenes with electron-donating groups was much better owing to the
electronic effect (Table 2, entries 8-12).Meanwhile, the steric effect also had obvious influence on
the catalytic performance, such as, ortho-substituted substrates and meta-substituted substrates
exhibited obviously lower catalytic activity and chemoselectivity than para-substituted substrates
(Table 2, entries 6 vs 7, 8 vs 9, 10 vs 11). Similarly, the hydrogenation and N-alkylation reactions
between different alcohols and nitrobenzene proceeded with good to excellent activity and
chemoselectivity after 24 h with Pd/NH -MIL-101(Fe)-2MI(300) nanocomposite (Table 2, entries
2
1
3-15). The substrates could also be extended to nitrobenzene and alkyl alcohol, and the
conversion of nitrobenzene was 28%, and the chemoselectivity to N-alkylamine was 56% (Table
, entry 16).
2
Table 2. Light-induced one-pot hydrogenation and N-alkylation of nitrobenzenes with benzyl
alcohol over Pd/NH -MIL-101(Fe)-2MI(300)
2
Entry
Substrate
1
Aldehyde
4
Sel. /%
R1
H
R2
Conv./%
/μmol
1
2
3
4
5
6
7
8
9
Phenyl
100
75
76
71
80
37
82
89
96
91
96
91
76
90
70
28
96
86
84
88
87
86
95
90
92
90
94
93
88
93
85
56
139
126
124
133
156
199
128
174
151
112
142
159
67
o-Cl
Phenyl
Phenyl
Phenyl
Phenyl
Phenyl
Phenyl
Phenyl
Phenyl
Phenyl
Phenyl
Phenyl
p-Cl
p-F
p-CHO
o-COCH3
m-COCH3
o-OCH3
p-OCH3
o-CH3
p-CH3
p-OH
H
1
1
1
1
1
1
1
0
1
2
3
4
5
6
p-Methoxyphenyl
p-Methylphenyl
o-Methylphenyl
Propyl
H
119
45
H
H
24

Reaction conditions unless otherwise noted:
Pd/NH -MIL-101(Fe)-2MI(300) (based on Pd), K PO (0.2mmol), CH
irradiated for 24 h, conversion and chemoselectivity were analyzed by GC and GC-MS.
1
(0.1 mmol),
2
(3 mmol), 0.1 mmol%
CN (2 mL), N
2
, 0.75 W cm-2 blue LED,
2
3
4
3
Benzonitriles and their derivatives are wildly used in synthetic organic chemistry, chemical
industry and biological applications [65,66]. The one-pot hydrogenation and N-alkylation of
benzonitriles with alcohols was also attempted over Pd/NH -MIL-101(Fe)-2MI(300)
2
nanocomposite, and the reaction between the benzyl alcohol and benzonitrile (5) was adopted as
the model reaction (Table 3, entries 1-3). It was found that the one-pot hydrogenation and
N-alkylation product dibenzylamine (7) could be achieved with 57% conversion and 88%
chemoselectivity after irradiated for 24 h under N . Considering the reduction of nitrile group was
2
more difficult than nitro group, 1 atm H2 was introduced and the N-alkylation product
dibenzylamine (7) could be synthesized with 85% conversion and 94% chemoselectivity in 24 h,
when the reaction time was extended to 30 h, the benzonitrile conversion could reach 91% with
9
5% chemoselectivity to N-alkylamine (Table 3, entry 2). To the best of our knowledge, this is the
first N-alkylation report between benzonitriles and alcohols with heterogeneous catalysis. When
pure benzyl alcohol was used as the solvent, both the conversion of benzonitrile and the
chemoselectivity to N-alkylamine were decreased (Table 3, entry 3). Pd/NH -MIL-101(Fe)-2MI
2
was also used as the catalyst for the reaction under the same conditions, and the conversion rate of
benzonitrile was only 44% (Table 3, entry 4). The conversion decrease further proved that
calcination to form "quasi-MOF" could improve the photocatalytic performance. The reaction
could not be carried out in the dark at 80 °C (Table 3, entry 5). Different substituted benzyl
alcohols and benzonitriles could also be converted to the corresponding N-alkyl anilines with
good activity and excellent chemoselectivity (Table 3, entries 6-12). Introduction of both strong
electron-withdrawing group (-CF ) and strong electron-donating group (-OMe) to the benzonitriles
3
obviously decreased the photocatalytic activity, however, the chemoselectivity was almost
maintained (Table 3, entries 6, 9). When the reaction time was extended to 48 h, the
p-Trifluoromethylbenonitrile conversion could reach 85% with 92% chemoselectivity to
N-alkylamine (Table 3, entry 6). When moderate electron-donating group substituted tolunitriles
were the substrates, slightly increase in photocatalytic activity along with almost maintained
chemoselectivity to N-alkylamines was observed (Table 3, entries 7-8 vs 2). The N-alkylation
reaction between different substituted benzyl alcohols and benzonitrile was also carried out, and
both the benzonitrile conversion and the chemoselectivity to N-alkylamines was decreased (Table
3
, entries 10-12). Both the steric bulk and the electronic nature of substrate influenced the
photocatalytic performance.
Table 3. Light-induced one-pot hydrogenation and N-alkylation of different benzonitriles with
alcohols over Pd/NH -MIL-101(Fe)-2MI(300).
2
5
Sel. /%
Aldehyde
BiA /μmol
-b
179
Entry
1a
5
2
Conv. /%
6
7
Benzonitrile
Benzyl alcohol
57
12
88

2
Benzonitrile
Benzyl alcohol
85(91)c
42
6
94(95)c
85
-
126
214
209
-
3d
4e
5f
6
Benzonitrile
Benzyl alcohol
15
12
-
-
Benzonitrile
Benzyl alcohol
44
86
2
-
Benzonitrile
Benzyl alcohol
-
-
p-Trifluoromethylbenonitrile
o-Tolunitrile
Benzyl alcohol
45(85)g
85
9
91(92)g
91
-
189
130
121
206
67
7
Benzyl alcohol
6
3
-
8
p-Tolunitrile
Benzyl alcohol
89(93)c
39(56)g
65
8
92(92)c
9
m-Anisonitrile
Benzonitrile
Benzyl alcohol
5
87(91)g 10
1
1
1
0
p-Methoxybenzyl alcohol
p-Methylbenzyl alcohol
o-Methylbenzyl alcohol
8
85
87
84
7
8
6
1
2
Benzonitrile
68
5
119
45
Benzonitrile
31
10
Reaction conditions unless otherwise noted:
5
(0.1 mmol),
2
(6 mmol), 0.1 mmol%
CN (2 mL), 1 atm H
, 0.75 W cm-2 blue
instead of H
. b “-”
referred to no products or negligible products were detected. c Irradiated for 30 h. d Benzyl alcohol (2 mL) was
Pd/NH -MIL-101(Fe)-2MI(300) (based on Pd), K CO
2
2
3
(0.2mmol), CH
3
2
LED, irradiated for 24 h, conversion and selectivity were analyzed by GC and GC-MS. a
N
2
2
used as a solvent. e Pd/NH
for 48 h.
-MIL-101(Fe)-2MI was used as catalyst. Without light irradiation, 80 C. Irradiated
f
o
g
2
With above catalytic system characterization and one-pot hydrogenation along with
N-alkylation reaction exploration, it is reasonable to clearly clarify the effect of "quasi-MOF"
structure on the photocatalytic performance in the Pd/MOFs photocatalytic system. The XPS of
Pd/NH -MIL-101(Fe)-2MI(300) confirmed that calcination to form a "quasi-MOF" structure
2
could promote the interaction between Pd NPs and organic nodes. This improved interaction could
reduce the band gap and improve the light absorption, charge separation, electron transfer along
with utilization in one-pot hydrogenation and N-alkylation reactions. Therefore,
Pd/NH -MIL-101(Fe)-2MI(300) exhibited better photocatalytic performance in comparison with
2
Pd/NH -MIL-101(Fe)-2MI.
2
In order to study the visible light induced activation of substrates in the
Pd/NH -MIL-101(Fe)-2MI(300) photocatalytic system, in situ DRIFTS test was conducted to
2
o
analyze the difference in nitro and alcohol activation in the dark at 50 C or under light irradiation
at room temperature with simulated photocatalytic conditions. Nitrobenzene and p-methylbenzyl
alcohol were used as the substrates, and in situ DRIFTS showed the relative changes in the
catalytic system (Figure 9). The baseline spectrum was tested before light irradiation or heating.
The following characteristic peaks decreasing or increasing were obviously observed in the in situ
DRIFTS during light irradiation or heating, such as the decrease in tensile vibration of O-H bond
-1
in p-methylbenzyl alcohol between 3300 and 3700 cm ; the decrease in asymmetric tensile
-1
vibration of N-O bond in nitrobenzene between 1500 and 1600 cm ; the decrease in the O-H
in-plane deformation vibration and C-O tensile vibration in p-methylbenzyl alcohol around 1200
-1
and 1100 cm [67,68]; meanwhile, the increase in the aldehyde group C-H bond stretching
-1
vibration around 3200 cm ; the increase in C-N stretching vibration in product
-1
N-(4-methylbenzyl) aniline at about 850 cm [69]. With Pd/NH -MIL-101(Fe)-2MI(300) catalyst
2
o
in the dark at 50 C, the O-H tensile vibration, the N-O asymmetric tensile vibration, the O-H
in-plane deformation vibration and the C-O tensile vibration gradually decreased with heating
time increase, which should be related to the substrate catalytic activation with heating. For

comparison, the decrease in the O-H tensile vibration, the N-O asymmetric tensile vibration, the
O-H in-plane deformation vibration as well as the C-O tensile vibration with visible light
o
irradiation at 25 C was much faster than heating. Additionally, the increase in the aldehyde group
C-H bond stretching vibration and the N-alkylation product N-(4-methylbenzyl) aniline C-N bond
o
stretching vibration was evidently observed with visible light irradiation at 25 C. Obviously, the
activation efficiency promotion with visible light irradiation was much faster than that of heating
in the benzyl alcohol dehydrogenation, the nitro group reduction was well as the N-alkylation
product formation, which should be the key reason for the evident one-pot hydrogenation and
N-alkylation catalytic efficiency improvement with visible light.
Figure 9. In situ DRIFTS of the one-pot hydrogenation and N-alkylation of nitrobenzene with p-methylbenzyl
2
alcohol over Pd/NH -MIL-101(Fe)-2MI(300).
Mechanism for the light induced one-pot hydrogenation and N-alkylation of nitrobenzene
with benzyl alcohol over Pd/NH -MIL-101(Fe)-2MI(300) could therefore be proposed (Scheme1).
2
When NH -MIL-101(Fe)-2MI(300) was irradiated with light, Fe -µ -oxo clusters were excited to
2
3
3
generate electrons and holes (step i). Photogenerated electrons on NH -MIL-101(Fe)-2MI(300)
2
would reduce the adsorbed of Pd2+ to Pd NPs, and then other photogenerated electrons were
transferred from NH -MIL-101(Fe)-2MI(300) to Pd NPs to form electron-rich Pd species (step
2
ⅱ
). Meanwhile, benzyl alcohol adsorbed on the surface reacted with photogenerated holes to
create alkoxide intermediate (step ⅲ). Subsequently, the alkoxide intermediate was further
oxidized by photogenerated holes, and C-H was cleaved to form benzaldehyde, accompany with
the hydrogen transferred to the electron-rich Pd to generate Pd-H hydride (step ⅳ). Part of Pd-H
hydride was utilized to reduce nitrobenzene to aniline (step ⅴ). The Lewis acidic Fe3+ in
NH -MIL-101(Fe)-2MI(300) promoted the condensation between the benzaldehyde and aniline to
2
form an imine (step ⅵ). Finally, another part of the hydride of Pd-H was used to reduce the imine
to a secondary amine (step ⅶ). N-Alkylation of benzonitriles with alcohols should be preceded
through a similar hydrogen auto-transfer mechanism. In addition, the photocatalytic performance
improvement with morphology change and "quasi-MOF" structure construction should mainly be
related to the promotion in photoelectrons and holes separation efficiency, along with the electrons
transformation capability, which was confirmed by the change in photocurrent and
electrochemical impedance.

Scheme1. Plausible reaction mechanism for the visible-light induced one-pot synthesis of N-alkylamine.
. Conclusion
3
In conclusion, Fe-MOFs with different crystal size, morphology and crystalline structure
were constructed with strategies of ligand structure change and 2-MI coordinated modulation.
XRD revealed that the presence of 2-MI did not change the coordination mode of MIL-101(Fe)
and NH -MIL-101(Fe). After Pd loading with double solvent impregnation method, "quasi-MOF"
2
materials formation with retained morphology and Pd in situ photoreduction with visible light,
highly efficient one-pot photocatalytic hydrogenation and N-alkylation of a broad range of
nitrobenzenes and benzonitriles with alcohols were carried out with above constructed
multifunctional catalytic materials. The Fe-MOFs crystal size, morphology, crystalline structure
alteration and "quasi-MOF" structure construction were demonstrated to have obvious influence
on the photocatalytic performance of one-pot multi-step continuous catalytic step hydrogenation
and N-alkylation reactions. With strong interaction formed between Pd NPs and inorganic nodes
in "quasi-MOF" Pd/NH -MIL-101(Fe)-2MI(300), nitrobenzene photocatalytic one-pot
2
hydrogenation and N-alkylation chemoselectivity promotion from 86% to 96% was achieved. This
work established a highly efficient way to realize N-alkyl amines from nitrobenzenes or
benzonitriles and alcohols via a successful coupling of the ligand structure and 2-MI based crystal
size, morphology and crystalline structure optimization in Fe-MOFs, double solvent impregnation
method based Pd loading into Fe-MOFs, "quasi-MOF" based strong interaction between Pd NPs
and inorganic nodes, as well as Pd NPs based one-pot multi-step hydrogenation. In situ DRIFTS
o
spectra verified that substrates activation with visible light irradiation at 25 C was much faster
than heating in one-pot hydrogenation and N-alkylation reaction. This work highlights the great
potential of multifunctional photocatalysis in light-induced one-pot multi-step organic
transformation.
Acknowledgements

This work was financially supported by Natural Science Foundation Project of CQ
No. cstc2018jcyjAX0735, cstc2019jcyj-msxmX0641), National Natural Science
(
Foundation of China (No. 21201184), Ministry of Education of Chongqing (No.
KJQN201900811), Chongqing Technology and Business University (950119090) and
Chongqing Key Laboratory of Catalysis and New Environmental Materials
(KFJJ2019082).
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Declaration of interests
☒
The authors declare that they have no known competing financial interests or personal
relationships that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which
may be considered as potential competing interests:

Highlights
1
. MOF morphology, crystalline structure alteration and "quasi-MOF"
construction affect photocatalytic performance.
2
. Efficient photocatalytic one-pot hydrogenation and N-alkylation of
nitrobenzenes and benzonitriles.
3
. N-alkylation of benzonitriles with alcohols was achieved firstly in
heteroegeneous catalysis.
4
. Reaction mechanism was proposed with the assistance of in situ DRIFTS.