Borrowing hydrogen activity of NH2-MIL-125 for N-alkylation of amines with alcohols under solvent and base free condition

Article abstract of DOI:10.1016/j.catcom.2020.106085

The NH₂-MIL-125 showed excellent activity in solvent and base free N-alkylation of amines with alcohols via borrowing hydrogen mechanism. The Ti–O clusters of NH₂-MIL-125 provide acidic-basic active sites for the catalysis of reaction. The NH₂-MIL-125 was found to be stable and reusable in the reaction.

Full text of DOI:10.1016/j.catcom.2020.106085

Journal Pre-proof
Borrowing hydrogen activity of NH2-MIL-125 for N-alkylation
of amines with alcohols under solvent and base free condition
Nisha B. Patel, Naresh Vala, Atindra Shukla, Subhadip Neogi,
Manish Kumar Mishra
PII:
S1566-7367(20)30161-8
DOI:
https://doi.org/10.1016/j.catcom.2020.106085
CATCOM 106085
Reference:
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
1 March 2020
26 May 2020
9 June 2020
Please cite this article as: N.B. Patel, N. Vala, A. Shukla, et al., Borrowing hydrogen
activity of NH2-MIL-125 for N-alkylation of amines with alcohols under solvent and
base free condition, Catalysis Communications (2019), https://doi.org/10.1016/
j.catcom.2020.106085
This is a PDF file of an article that has undergone enhancements after acceptance, such
as the addition of a cover page and metadata, and formatting for readability, but it is
not yet the definitive version of record. This version will undergo additional copyediting,
typesetting and review before it is published in its final form, but we are providing this
version to give early visibility of the article. Please note that, during the production
process, errors may be discovered which could affect the content, and all legal disclaimers
that apply to the journal pertain.
© 2019 Published by Elsevier.

Journal Pre-proof
Borrowing hydrogen activity of NH2-MIL-125 for N-alkylation of amines with alcohols
under solvent and base free condition
Nisha B. Patel,a Naresh Vala,b Atindra Shukla,b Subhadip Neogi,c Manish Kumar Mishraa,*
aDepartment of Chemistry, Sardar Patel University,
Vallabh Vidyanagar- 388 120, Gujarat, India.
bShah-Schulman Center for Surface Science and Nanotechnology,
Dharmsinh Desai University, College Road, Nadiad – 387 001, Gujarat, India.
cDepartment of Inorganic Materials and Catalysis, Central Salt and Marine Chemicals Research Institute
(CSMCRI), Council of Scientific and Industrial Research (CSIR), GB Marg, Bhavnagar 364002, Gujarat, India .
E-mail: manishorgch@gmail.com; Tel: +91 2692 226856
Abstract
The NH2-MIL-125 showed excellent activity in solvent and base free N-alkylation of amines
with alcohols via borrowing hydrogen mechanism. The Ti–O clusters of NH2-MIL-125 provide
acidic-basic active sites for the catalysis of reaction. The NH2-MIL-125 was found to be stable
and reusable in the reaction.
Keywords: Borrowing hydrogen methodology; metal-organic frameworks; NH2-MIL-125; N-
alkylation of amines; alcohols.
1

Journal Pre-proof
1. Introduction
Borrowing hydrogen methodology is an atom efficient and greener approach for the synthesis of
chemicals using alcohols as inexpensive and green alkylating reagent [1]. This methodology
involves the activation of an alcohol (I) by removal of hydrogen (H2; dehydrogenation) to a
carbonyl (II) for the reaction with a nucleophile (Nu; carbanions/ amines) to an unsaturated
product (III), followed by hydrogenation using H2 generated in dehydrogenation step to finally
saturated product (IV) (Scheme 1) [2]. The borrowing hydrogen method has been adapted to use
alcohols as an alkylating agent in alkylation of carbonyls (C-alkylation) [3-7] and amines (N-
alkylation) [5-11] under greener route. The noble metals in the form of homogeneous as well as
heterogeneous catalysts have shown excellent activity in the borrowing hydrogen reactions (see
Table S1 & S2). The bases/ additives and solvents are used with most of these reported catalysts,
which detriment the eco-friendly nature of the process. The borrowing hydrogen methodology is
still in need of suitable heterogeneous catalytic system involving less precious metal, and no
base/ additive and solvent for its viable application.
Alkylation
R'
R
OH
R
Y
(I)
(IV)
Dehydro-
genation
Hydrogen
transfer
Catalyst
Catalyst-H2
Reaction of
Nu (R'-Y)
R'
Y
R
R
O
-H2O
(II)
(III)
Nu: carbanion/ amine
Y: nucleophilic C or N
Scheme 1. Activation of an alcohol for C-/ N-alkylation via borrowing hydrogen mechanism.
2

Journal Pre-proof
Metal-organic frameworks (MOFs) possess attractive features such as high surface area, high
porosity, and tunable textural and functional characteristics [12], which make them very suitable
for their exploration as catalysts and support materials in the area of heterogeneous catalysis.
There has been significant progress on exploration of MOFs in heterogeneous catalysis [13]. The
NH2-functionalized MIL-125 (NH2-MIL-125) is one of the stable MOFs [14], which has been
much investigated for the development of efficient visible light active photocatalysts [13]. We
were interested to study the activity of NH2-MIL-125 for borrowing hydrogen catalysis under
thermal condition, because of its excellent stability and basicity due to –NH2 functionality [15],
which can trigger the alcohols for dehydrogenation through deprotonation [16]. We found that
NH2-MIL-125 exhibited excellent borrowing hydrogen activity giving good conversion of
alcohols in N-alkylation of amines. The Ti–O clusters of NH2-MIL-125 provide active sites (Ti–
and O– as Lewis acidic and basic sites, respectively) for the catalysis of borrowing hydrogen
reaction. The study opens up a new area of catalytic application for NH2-MIL-125 and other
MOFs, and provides a solvent and base free catalytic route for borrowing hydrogen reactions.
2. Experimental
2.1. Synthesis of NH2-MIL-125 and MIL-125
NH2-MIL-125 and MIL-125 materials were prepared by a solvothermal route, which is a slightly
modified method reported by H. Yamashita [17]. For the synthesis of NH2-MIL-125, a solution
of titanium tetra iso-propoxide (3.5 mmol) and 2-aminoterephthalic acid (7 mmol) in a 50 mL
mixture of DMF and methanol (1:1; v/v) was prepared by stirring at room temperature (30°C).
The solution was transferred to a 150 mL Teflon-lined autoclave and heated at 150°C for 48 h in
an oil bath. The solution was cooled to room temperature. A solid mass was obtained after
3

Journal Pre-proof
filtration, which was washed with DMF (N,N-dimethylformamide; 50 mL) and then with
methanol (50 mL). The solid mass was activated under vacuum at 150°C for 15 h. MIL-125 was
also synthesized by solvothermal reaction of titanium tetra iso-propoxide (9 mmol) with
terephthalic acid (15 mmol) in a 50 mL mixture of DMF and methanol (9:1; v/v) as described
above for NH2-MIL-125. The characteristics of the synthesized NH2-MIL-125 and MIL-125 are
given in electronic supplementary information (ESI).
2.2. General procedure for N-alkylation of amines with alcohols
A mixture of amine and alcohol in required molar ratio along with the catalyst were taken in a 50
mL round bottom flask equipped with a water cooled condenser. The mixture was heated at
desired temperature under stirring for required period of time. After the completion of reaction,
the reaction mixture was cooled and diluted with methanol (2 mL). The diluted reaction mixture
was centrifuged to separate the catalyst from the liquid phase and the reaction mixture was
analyzed by gas chromatography to calculate the conversion of alcohol and selectivity of
products (see ESI).
3. Results and discussion
Initially, the catalytic activity of NH2-MIL-125 was assessed for N-alkylation of aniline (1) with
benzyl alcohol (2), as a model reaction, using their equimolar amount (10 mmol) and 10 wt.% of
catalyst at 100C to 180C for 15 h (Table 1). The reaction at 160C gave highest conversion of
2 (97%) into 95% N-alkylated product (3) showing 160C to be optimum temperature for
borrowing hydrogen activity of NH2-MIL-125. At lower (140C) and higher (180C)
temperatures, the imine product (4) was in significant amount. The increase in molar amount of
4

Journal Pre-proof
either 1 or 2 decreased the conversion of alcohol as well as selectivity of 3 (Table 1). This is an
advantage with NH2-MIL-125 that substantially high conversion of alcohol is achieved with
equimolar amount of alcohol; many heterogeneous catalysts require higher molar quantity of
alcohol to give a high conversion to N-alkylated product (Table S2). The results (Table 1) show
excellent activity of NH2-MIL-125 for borrowing hydrogen reaction giving highest conversion of
alcohol and selective formation of N-alkylated product in equimolar reaction of an amine and an
alcohol at catalytic amount (10 wt.%). The kinetics of the reaction (equimolar reaction of 1 and 2
using 10 wt.% catalyst at 160C; Table 1) depicts that 15 h reaction gives highest conversion of
2 (97%) with highest selectivity of 3 (95%). Generally, longer reaction time (24-72 h) is required
with most of heterogeneous catalysts to achieve highest yield (Table S2). The longer reaction
with NH2-MIL-125 reduces the selectivity of 3 (Table 1) due to its conversion
(dehydrogenation) into 4. The oxidative dehydrogenation of a secondary amine (3) into imine (4)
has been reported over Au/TiO2 catalyst [18]. The formation of significant amount of 4 in some
of the reactions (Table 1) is a clear evidence of the borrowing hydrogen mechanism, which
involves the formation of imine intermediate followed by hydrogenation with hydrogen
generated during dehydrogenation of alcohol [2]. The direct nucleophilic substitution of
alcoholic –OH of benzyl alcohol by –NH2 of aniline is another possible mechanism for the
formation of N-alkylated product [19,20]. The dehydrogenative activity of NH2-MIL-125 was
evaluated for dehydrogenation of 2 at 160C in absence of 1; 79% conversion of 2 into 95%
benzaldehyde (along with 5% dibenzyl ether) was obtained. The formation of significant amount
of imine intermediate (4) in the reactions and dehydrogenative activity of NH2-MIL-125 (in
dehydrogenation of 3 to 4 and 2 to benzaldehyde) reveal the occurrence of N-alkylation reaction
via borrowing hydrogen mechanism.
5

Journal Pre-proof
Table 1. Optimization of reaction parameters (temperature, catalyst amount, molar ratio of
reactants and reaction time) for NH2-MIL-125 catalyzed N-alkylation of 1 with 2.
O H
N H
H N
N
2
N H 2 -M IL-12 5
+
+
(2 )
(3 )
(1 )
(4 )
Reaction parameter
Conv. (%) of 2 Select. (%) of 3 Select. (%) of 4
Temperature (°C)a
100
120
140
160
180
0
0
20
97
92
75
95
72
25
5
27
Catalyst amount (wt.%)b
10
5
2.5
97
60
30
95
99
99
5
1
1
Molar ratio of 1 and 2c
1:1
1:2
2:1
97
21
22
95
42
8
5
58
68
Reaction time (h)d
1
2
3
6
9
12
15
18
24
48
25
30
50
75
84
90
97
97
98
98
99
99
99
99
99
99
95
87
10
1
1
1
1
1
1
1
5
13
90
99
a10 mmol 1, 10 mmol 2, 10 wt.% NH2-MIL-125, 15 h.
b10 mmol 1, 10 mmol 2, 160°C, 15 h.
c10 wt.% NH2-MIL-125, 160°C, 15 h.
d10 mmol 1, 10 mmol 2, 10 wt.% NH2-MIL-125, 160°C.
The dehydrogenation of an alcohol can occur over acidic and basic sites located in vicinity [21].
The defect metal sites (Ti–) and O–atoms of Ti–O clusters of NH2-MIL-125 may provide vicinal
Lewis acidic and Lewis basic sites, respectively [15] to catalyze dehydrogenation-hydrogen
6

Journal Pre-proof
transfer (i.e., borrowing hydrogen) reaction. The direct involvement of –NH2 group of NH2-MIL-
125 as basic site in catalysis of borrowing hydrogen can also be anticipated. However, the
substantial conversion of 2 (65%) into 3 (83%) with MIL-125 in the reaction (equimolar reaction
of 1 and 2 using 10 wt.% catalyst at 160C for 15 h) reveals that Ti– and O–atoms of metal
cluster are possibly catalytic sites. In a Ti–O cluster of NH2-MIL-125, Ti–atom is coordinated
with six O–atoms, which can act as basic sites: three O–atoms provided by carboxylates, one O–
atom of bridging hydroxo group, and two bridging O–atoms joining two Ti– atoms [22]. The
titania (prepared by a sol-gel method [23]; ESI), in which Ti–atom has only bridging hydroxo
and bridging O–atoms but no carboxylates’ O–atom, gave 29% conversion of 2 into 4 (100%) in
the equimolar reaction of 1 and 2 [10 mmol 1, 10 mmol 2, 10 wt.% catalyst, 160°C, 15 h],
without formation of 3. This indicates that the carboxylates’ O–atoms are active basic sites for
borrowing hydrogen activity.
The Ti– and carboxylates’ O–atoms of a Ti–O cluster can dehydrogenate 2 to a carbonyl
intermediate (benzaldehyde) by abstracting hydroxyl hydrogen of 2 as proton and a benzylic
hydrogen, respectively (Scheme 2). However, we did not observed benzaldehyde in reaction
mixture by GC analysis, probably due to its adsorption over the sites and prompt nucleophilic
reaction of 1 converting into 4. The hydride and proton abstracted by Ti– and carboxylates’ O–
atoms, respectively, are transferred to 4 to produce 3 (Scheme 2). The mesomeric (+M) effect of
–NH2 can enhance electron density at carboxylates’ O–atoms in NH2-MIL-125 making them
more basic than carboxylates’ O–atoms in MIL-125 and therefore, NH2-MIL-125 showed higher
catalytic activity. The addition of an organobase, 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD;
20%), in a reaction with MIL-125 increased the conversion (65% to 85%) but greatly decreased
the selectivity of N-alkylated product (11%). This result indicates that use of additional base
7

Journal Pre-proof
facilitates the dehydrogenation reaction by helping in deprotonation and giving benzaldehyde
and its conversion into imine, however, the protons abstracted by TBD molecules are not
transferred to imine for reduction giving poor selectivity of N-alkylated product. This result
shows that the metal- and basic- sites should be in vicinity for effective hydrogen transfer, which
is possible in NH2-MIL-125 or in MIL-125.
A d s o rp tio n
&
d e h yd ro g e n a tio n
Im in a tio n
H yd ro g e n tra n s fer
P h
-
P h
P h
T i-O c lu ster
P h
P h
H
H
T i
O
(1 )
T i
O
N H
T i
O
(2 )
2
O H
O
O
O
O
N
(4 )
-H
O
N H
2
H
H
+
P h
2
P h
(3)
N H
N H
N H
2
2
N H -M IL -1 2 5
2
Scheme 2. Plausible mechanism of N-alkylation of 1 with 2 via borrowing hydrogen reaction
over NH2-MIL-125.
Numerous expensive metal based homogeneous and heterogeneous catalysts have been studied
for N-alkylation of 1 with 2 (Table S1 & S2). These catalysts perform well in the presence of
excess amount of bases/ additives and solvent. NH2-MIL-125 is an inexpensive catalyst, which
exhibits similar activity (conversion/ yield) under bases/ additives and solvent free condition.
The catalytic efficiency of NH2-MIL-125 was also evaluated for N-alkylation of different
aromatic amines with alcohols under similar reaction condition as optimized above (Table 2).
The NH2-MIL-125 showed activity with all types of substrates. However, the nature of
substituents present in substrates affects the reaction (conversion and selectivity of N-alkylated
8

Journal Pre-proof
product). The presence of electron withdrawing groups (e.g., -NO2 and –F; Entry 4, 5, 8 & 9;
Table 2) in amines/ alcohols slowed down the reaction giving less conversion of alcohol.
Table 2. Conversion and selectivity in NH2-MIL-125 catalyzed N-alkylation reactions of amines
with alcohols.a
Alcohol
N-alkylated product
Imine product
Entry Amine
(Conv.; %)
(Select.; %)
(Select.; %)
OH
HN
N
NH2
1
(95)
(5)
(97)
OH
HN
N
NH2
OCH3(97, 94b)
OCH3(3)
2
OCH
3
(97)
OH
HN
N
NH2
CH3(8)
3
CH
3 (92)
CH
3
(81)
OH
HN
N
NH2
NO2(10, 49c)
NO2 (90, 51c)
4
(5, 28c)
NO
2
OH
HN
N
NH2
F(99)
F(1)
5
F
(28)
OH
HN
N
NH
2
6
7
8
(86)
OCH3
OCH
N
3
(99)
(1)
(1)
(1)
(1)
OCH
3
HN
NH
2
OH
(59)
CH3
CH
N
3
CH
(99)
3
HN
NH
2
OH
(20, 40c)
NO2
NO
N
2
NO
2
(99)
HN
NH
2
OH
9
(27)
(99)
F
F
F
NH2
HN
5
5
10
OH (25)
(100)
a10 mmol amine, 10 mmol alcohol, 10 wt.% NH2-MIL-125, 160°C, 15 h.
bIsolated yield.
cReaction time: 24 h.
9

Journal Pre-proof
An electron withdrawing group in alcohol may reduce electron density on oxygen of –OH group
through a long range inductive effect [24], which may adversely affect alcohol-acidic site
interaction through oxygen of –OH group thus slowing down adsorption and dehydrogenation
and giving less conversion of alcohol. The less selectivity of N-alkylated products with nitro
derivative of alcohol (Entry 4; Table 2) shows reduced hydrogen transfer, probably due to much
slow adsorption and dehydrogenation processes. The presence of an electron withdrawing group
in aromatic amines (Entry 8 and 9; Table 2) may reduce their nucleophilicity (electron density at
N) slowing down the imination step or formation of corresponding imine product and lowering
the conversion of alcohol. The longer reaction time increased the conversion of alcohol as well
as selectivity of N-alkylated products (Entry 4 and 8; Table 2). NH2-MIL-125 also exhibited
activity in N-alkylation with an aliphatic alcohol, n-hexanol (Entry 10; Table 2). The boiling
point of n-hexanol (157°C) is close to the reaction temperature (160°C). During the reaction, n-
hexanol will be mostly in vapor phase, which will minimize its contact with catalyst and aniline
present in liquid phase. Therefore, the conversion of n-hexanol was less (25%). The conversion
of alcohols having low boiling points can be improved by carrying out reactions in a sealed/
pressurized vessel [10].
The spent NH2-MIL-125 was separated by filtration, washed with methanol (5 mL) and dried at
100°C for 6 h, and then was used in subsequent three reaction cycles under similar reaction
condition. The spent catalyst was found to be reusable without significant loss in catalytic
activity (98% conversion and 97% selectivity of 3 after third cycle). Furthermore, the
characteristics of spent catalyst (measured by XRD, FTIR and BET surface area analysis; ESI)
were observed to be similar to the fresh catalyst.
10

Journal Pre-proof
Conclusion
The NH2-MIL-125 was found to be an excellent catalyst for borrowing hydrogen reactions,
which was demonstrated for N-alkylation of amines with alcohols. The Ti– and carboxylates’ O–
atoms of Ti–O clusters are active sites for the catalysis of reaction. The NH2-MIL-125 was found
to be stable in the reaction showing reusability. This report suggests to study the catalytic activity
of different MOFs, especially NH2-functionalized MOFs, for borrowing hydrogen reactions.
Acknowledgement
The authors are thankful to Department of Science and Technology (DST), New Delhi, India for
providing financial support (File No.: EMR/2016/000896), to the Vice-chancellor, D.D.
University for providing analytical support, and to Department of Chemistry, S.P. University for
support under CPEPA and CAS programs.
References
[1] A. Corma, J. Navas, M.J. Sabater, Advances in one-pot synthesis through borrowing
hydrogen catalysis, Chem. Rev. 118 (2018) 1410–1459.
[2] A.J.A. Watson, J.M.J. Williams, The give and take of alcohol activation, Science 329
(2010) 635–636.
[3] A. Charvieux, J.B. Giorgi, N. Duguet, E. Métay, Solvent-free direct α-alkylation of ketones by
alcohols catalyzed by nickel supported on silica–alumina, Green Chem. 20 (2018) 4210–4216.
[4] F. Huang, Z. Liu, Z. Yu, C-Alkylation of Ketones and Related Compounds by Alcohols:
Transition-Metal-Catalyzed Dehydrogenation, Angew. Chem. Int. Ed. 55 (2016) 862–875.
11

Journal Pre-proof
[5] T. Irrgang, R. Kempe, 3d-Metal Catalyzed N- and C-Alkylation Reactions via Borrowing
Hydrogen or Hydrogen Autotransfer, Chem. Rev. 119 (2019) 2524-2549.
[6] B.G. Reed-Berendt, K. Polidano, L.C. Morrill, Recent advances in homogeneous borrowing
hydrogen catalysis using earth-abundant first row transition metals, Org. Biomol. Chem. 17
(2019) 1595–1607.
[7] M. Dixit, M. Mishra, P.A. Joshi, D.O. Shah, Clean borrowing hydrogen methodology
using hydrotalcite supported copper catalyst, Catal. Commun. 33 (2013) 80–83.
[8] C. Risi, M. Calamante, E. Cini, V. Faltoni, E. Petricci, F. Rosatia, M. Taddei, In water
alkylation of amines with alcohols through a borrowing hydrogen process catalysed by
ruthenium nanoparticles, Green Chem. 22 (2020) 327–331.
[9] A.K. Bains, A. Kundu, S. Yadav, D. Adhikari, Borrowing Hydrogen-Mediated N-
Alkylation Reactions by a Well-Defined Homogeneous Nickel Catalyst, ACS Catal. 9
(2019) 9051–9059.
[10] X. Liu, P. Hermange, J. Ruiz, D. Astruc, Pd/C as an efficient and reusable catalyst for the
selective N-alkylation of amines with alcohols, ChemCatChem 8 (2016) 1043–1045.
[11] H. Yang, X. Cui, X. Dai, Y. Deng, F. Shi, Carbon-catalysed reductive hydrogen atom
transfer reactions, Nat. Commun. 6 (2015) 6478-6488.
[12] H. Furukawa, K.E. Cordova, M. O’Keeffe, O.M. Yaghi, The chemistry and applications of
metal-organic frameworks, Science 341 (2013) 974–986.
[13] A. Dhakshinamoorthy, Z. Li, H. Garcia, Catalysis and photocatalysis by metal organic
frameworks, Chem. Soc. Rev. 47 (2018) 8134–8172.
12

Journal Pre-proof
[14] S. Yuan, L. Feng, K. Wang, J. Pang, M. Bosch, C. Lollar, Y. Sun, J. Qin, X. Yang, P.
Zhang, Q. Wang, L. Zou, Y. Zhang, L. Zhang, Y. Fang, J. Li, H.-C. Zhou, Stable metal–
organic frameworks: design, synthesis, and applications, Adv. Mater. 30 (2018) 1704303.
[15] S.-N. Kim, J. Kim, H.-Y. Kim, H.-Y. Cho, W.-S. Ahn, Adsorption/catalytic properties of
MIL-125 and NH2-MIL-125, Catal. Today 204 (2013) 85–93.
[16] X. Wang, D.Z. Wang, Aerobic oxidation of secondary benzylic alcohols and direct
oxidative amidation of aryl aldehydes promoted by sodium hydride, Tetrahedron 67 (2011)
3406–3411.
[17] M. Martis, K. Mori, K. Fujiwara, W.-S. Ahn, H. Yamashita, Amine-functionalized MIL-
125 with imbedded palladium nanoparticles as an efficient catalyst for dehydrogenation of
formic acid at ambient temperature, J. Phys. Chem. C 117 (2013) 22805−22810.
[18] A. Grirrane, A. Corma, H. Garcia, Highly active and selective gold catalysts for the aerobic
oxidative condensation of benzylamines to imines and one-pot, two-step synthesis of
secondary benzylamines, J. Catal. 264 (2009) 138–144.
[19] M.M. Reddy, M.A. Kumar, P. Swamy, M. Naresh, K. Srujana, L.Satyanarayana, A.
Venugopala, N. Narender,N-alkylation of amines with alcohols over nanosized zeolite beta,
Green Chem. 15 (2013) 3474–3483.
[20] K.N. Tayade, M. Mishra, Munusamy K., R.S. Somani, Solvent free acid catalysed direct
N-alkylation of amines with alcohols using Al grafted MCM-41, J. Mol. Catal. A: Chem.
390 (2014) 91–96.
[21] V.K. Díez, C.R. Apesteguía, J.I. Di Cosimo, Effect of the chemical composition on the
catalytic performance of MgyAlOx catalysts for alcohol elimination reactions, J. Catal. 215
(2003) 220–233.
13

Journal Pre-proof
[22] D. Sun, W. Liu, Y. Fu, Z. Fang, F. Sun, X. Fu, Y. Zhang, Z. Li, Noble metals can have
different effects on photocatalysis over metal-organic frameworks (MOFs): a case Study
on M/NH2-MIL-125(Ti) (M=Pt and Au), Chem. Eur. J. 20 (2014) 4780–4788.
[23] V.G. Gandhi, M.K. Mishra, M.S. Rao, A. Kumar, P.A. Joshi, D.O. Shah, Comparative
study on nano-crystalline titanium dioxide catalyzed photocatalytic degradation of
aromatic carboxylic acids in aqueous medium, J. Ind. Eng. Chem. 17 (2011) 331–339.
[24] R. Tandon, T.A. Nigst, H. Zipse, Inductive Effects through alkyl groups-How long is long
enough?, Eur. J. Org. Chem. 24 (2013) 5423–5430.
14

Journal Pre-proof
CRediT author statement
Nisha B. Patel: investigation,
Naresh Vala: validation,
Atindra Shukla: resources,
Subhadip Neogi: resources,
Manish Kumar Mishra: Conceptualization, methodology, supervision, writing, reviewing, and
editing.
15

Journal Pre-proof
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:
Not applicable
Ref.: Manuscript (CATCOM-D-20-00169) titled “Borrowing hydrogen activity of NH2-MIL-
125 for N-alkylation of amines with alcohols under solvent and base free condition”.
Authors: Nisha B. Patel, Naresh Vala, Atindra Shukla, Subhadip Neogi, Manish Kumar Mishra
Dr. Manish Kumar Mishra
Date: 25/05/2020
16

Journal Pre-proof
Department of Chemistry, Sardar Patel University
Vallabh Vidyanagar-388 120, Gujarat, India
17

Journal Pre-proof
O H
H N
N H
2
v ia
N o s o lv en t
&
B o rro w in g
h yd ro g e n
R
+
n o ba s e
m e ch a n is m
R
R
R
(3 )
(1 )
(2)
N H 2 -M IL -1 2 5
(s ta ble
& re u sa b le
ca ta lys t)
18

Journal Pre-proof
Research highlights
 Excellent borrowing hydrogen activity of NH2-MIL-125.
 Solvent and base free N-alkylation of amines with alcohols using NH2-MIL-125.
 Catalysis of reaction by Ti–O clusters of NH2-MIL-125.
 Stability and reusability of NH2-MIL-125 in the reaction.
19