Heterometallic {ZnEu}-metal-organic framework for efficient chemical fixation of CO2

Article abstract of DOI:10.1039/d0dt02730h

Based on a ligand-directed synthetic strategy, the acidic solvothermal reaction of ZnO, Eu2O3, and 4,4′,4″-(pyridine-2,4,6-triyl)tri(1,3-benzenedicarboxylic acid) (H6PTTBA) generated a targeted robust double-walled honeycomb material {[EuIIIZnII(HPTTBA)(H2O)]·4DMF·3H2O}n (simplified as NUC-9), which featured excellent characteristics such as dual tubular nanochannels, high porosity, specific surface area, abundant exposed active metal sites, etc. Although both types of nano-channels (I and II) alternately arranged in the lattice and shaped by six rows of [EuIIIZnII(CO2)6(H2O)] SBUs possessed an equal amount of exposed active metal sites, they could be differentiated according to the discrepant inner surface functionalized by free carboxyl oxygen atoms or coordinated aqueous molecules. Moreover, an activated sample of NUC-9 exhibited better catalytic performance than documented Zn- or Eu-based MOFs for the chemical transformation of various epoxides into the related carbonates under comparatively mild conditions of 1 atm CO2 flow and 70 °C, which should be ascribed to the unsaturated Zn2+ and Eu3+ ions acting as strong Lewis acid sites and free carboxyl oxygen atoms as basic sites synergistically polarizing and activating the substrates of epoxides and CO2 and consequently promoting the reaction. Furthermore, the water-resistant framework of NUC-9 could selectively and sensitively discriminate Fe3+ in aqueous solution according to the fluorescence quenching effect. In addition, it is worth mentioning that the successful self-assembly of NUC-9 provides an effective synthetic technique by employing the designed favorable organic ligand for achieving the targeted functional model of MOFs. This journal is

Full text of DOI:10.1039/d0dt02730h

View Article Online
View Journal
Dalton
Transactions
An international journal of inorganic chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: X. Zhang, L.
Hongxiao, H. Chen and L. Fan, Dalton Trans., 2020, DOI: 10.1039/D0DT02730H.
Volume 46
Number 10
This is an Accepted Manuscript, which has been through the
1
4
March 2017
Pages 3073-3412
Royal Society of Chemistry peer review process and has been
accepted for publication.
Dalton
Transactions
An international journal of inorganic chemistry
rsc.li/dalton
Accepted Manuscripts are published online shortly after 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
Information for Authors.
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 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 0306-0012
COMMUNICATION
Douglas W. Stephen et al.
N-Heterocyclic carbene stabilized parent sulfenyl, selenenyl,
and tellurenyl cations (XH , X = S, Se, Te)
+
rsc.li/dalton

View Article Online
DOI: 10.1039/D0DT02730H
Page 1 of 9
Dalton Transactions
One Heterometallic {ZnEu}-Metal-Organic Framework for Efficient
Chemical Fixation of CO2
Hongxiao Lv, Hongtai Chen, Liming Fan and Xiutang Zhang*
Department of Chemistry, College of Science, North University of China, Taiyuan 030051, People’s Republic of China. E-mail: xiutangzhang@163.com;
Received (in XXX, XXX) 1st January 2019, Revised Manuscript received 1st January 2019
Based on the ligand-directed synthetic strategy, the acidic solvothermal reaction of ZnO, Eu
2
O
3
,
and
4
,4′,4′′-(pyridine-2,4,6-triyl)tri(1,3-benzenedicarboxylic acid) (H
6
PTTBA) generated one targeted robust double-walled
III
II
honeycomb material of {[Eu Zn (HPTTBA)(H
2
O)]4DMF3H
2
n
O} (simplified as NUC-9), which featured the excellent
characteristics of dual tubular nanochannels, high porosity and specific surface area, abundant exposed active metal sites, ect.
Although both types of nano-channels (I and II) alternately arranged in the lattice and shaped by six rows of
III
II
[
2 6 2
Eu Zn (CO ) (H O)] SBUs possessed the equal amount of exposed active metal sites, they could be differentiated according to
the discrepant inner surface funthionalized by free carboxyl oxygen atoms or coordinated aqueous molecules. Moreover, the
activated sample of NUC-9 exhibited the better catalytic performance than documented Zn- or Eu-based MOFs for the chemical
transformation of various epoxides into the related carbonates under comparatively mild conditions of 1 atm CO
°
2
flow and 70
C, which should be ascribed to that unsaturated ions of Zn2+ and Eu3+ as strong Lewis acid and free carboxyl oxygen atoms as
2
basic sites could synergistically polarize and activate the substrates of epoxides and CO and consequently prompt the reaction.
3
+
Furthermore, the water-resistant framework of NUC-9 could selectively and sensitively discriminate Fe in aqueous solution
according to fluorescence quenching effect. In addition, it's worth mentioning that the successful self-assembly of NUC-9
provides one effective synthetic technique by employing designed favorable organic ligand for achieving the targeted functional
model of MOFs.
CO
of CO
2
.5 Thus, in order to promote the selective adsorption capacity
in terms of kinetics and thermodynamics, the particular
Introduction
2
research interest for MOFs at present is concentrated on the
performance optimization by designing functional organic
ligands to adjust pore size, increasing the open metal sites to
The warming of the Earth and the consequent climatic changes
caused by greenhouse gases has become one of the greatest
threats facing mankind today, such as sea level rise, land
desertification, and extinction of some biological species.
2 2 4
Among all greenhouse gases (CO , N O, CH , etc), carbon
dioxide accounts for the largest proportion and its concentration
in the atmosphere has been steadily rising due to the persistently
excessive consumption of fossil fuels in the areas of thermal
power generation, industrialization, transportation vehicles, and
so on. Therefore, the strategic research on the capture-storage or
improve their adsorption affinity for CO
thermal and chemical stability (e.g. water resistance).
2
, and improving the
1
6
Among all documented MOFs, zinc cation, as one kind of
d-block metal ions and one potential strong Lewis acid , has been
paid close attention due to its distinctive characteristics including
electronic configuration, binding energy, and charge distribution,
which renders it various coupling affinities to multifarious donor
7
atoms from ligands. So far, quantum chemical calculation with
consumption of CO
issue. At present, catalytic conversion of captured CO
2
in the atmosphere has become one urgent
into fuel
ab initio calculations exhibited that the formation of
2
2
+
hexa-coordinated Zn cations was the most stable due to the
largest binding energies, which could be confirmed by the
absolute large proportion of Zn-MOFs constructed from
hexa-coordinated Zn2+ ions.8 Whereas, recently reported
or industrial raw materials is one of the most promotable ways to
jointly solve the environmental and energy challenges.2
Moreover, a series of research in recent years evidenced that
porous metal-organic frameworks (MOFs) could be taken as
effective heterogeneous catalysts for the chemical transformation
2
+
Zn-MOFs based on tetra-coordinated Zn ions with solvent-free
channels could display the better selective adsorption
2
of CO and epoxides into carbonates and meantime was superior
performance for guest molecules of CO
chemical transformation of epoxides with CO
alkyl carbonates due to that exposed active Zn ions as the
2
and catalyze the
to homogeneous catalysts in the aspect of product separation and
2
into according
3
catalyst recycling. Furthermore, the mild reaction conditions of
2
+
temperature and pressure by utilizing MOFs catalyst are
incomparable with other hetero- or homogeneous catalysts, for
instance, zeolites, inorganic metal salts or oxides, ionic liquids,
strong Lewis acid to polarize and activate CO
2
and the ring of
9
ethylene oxide via coordination affinity. So, the self-assembly of
nanoporous Zn-MOFs with the purpose of enhancing the amount
of exposed active tetra- or penta-coordinated Zn2+ cations will
become a research hotspot, especially for the application in the
areas of selectively separation or/and storage of guest molecules,
catalysis for some specific reaction, and optics.10
4
amine aqueous solutions, polymerized organics, etc. Whereas,
MOFs, as a kind of organic-inorganic hybrid material with
marvellous structural adaptability, feature the excellent traits of
high specific surface area and syngenetic micropore size, which
consequently lead to the better unique adsorption performance for

View Article Online
DOI: 10.1039/D0DT02730H
Dalton Transactions
Page 2 of 9
Moreover, in the past decade, the research on the structure and
chemical bond theory of Ln-MOFs has been at its liveliness,
which led to a great deal of new research branches, such as
catalysts, monomolecular magnets, magnetic refrigeration
element analyzer of CE instrument. The powder X-ray diffraction
was collected for 2θ values on X-Pert pro diffractometer with
Cu-Kα radiation. Thermogravimetric analyses (TGA) were
performed on NETZSCH STA 449 F3 thermogravimetric
1
1
materials, and fluorescence recognition. So far, the documented
analyzer
(25-800℃,
10℃/min,
air
condition).
3
+
Ln-MOFs exhibit that the coordination modes of Ln could vary
in a wide range with the largest coordination number of 12 due to
the various orbital hybridization of fnd2+msp (n = 0−3, m = 1−3)
devoted by electron orbitals of 6s, 6p, 5d, and 4f, which lead to a
series of characteristics in accordance with the intrinsic
Single-component gas sorption measurements were performed
with an ASAP 2020 Plus instrument: N
were measured at 77K using liquid N
2
gas sorption isotherms
bath; CO gas sorption
3
2
2
isotherms were measured at 273K using ice-water bath and
298K using water bath. The catalytic yield was calculated and
1
2
3+
1
structures. Thus, although Ln ions included in documented
Ln-MOFs display the octa- or nano-coordinated modes, they
could still possess the strong Lewis acidity and show strong
affinities to small guest molecules with smaller steric resistance,
measured on a Thermo Fisher Trace ISQ GC/MS instrument. H
NMR and 13C NMR spectra were recorded on a JEOL-ECX 500
FT (500 and 125 MHz respectively) instrument in CDCl
3
or in
DMSO-d with n-dodecane as the internal standard as the internal
6
such as CO
framework of [Eu(BTB)(phen)] reported by Zhao and coworkers,
as the first sample of Ln-MOFs for the fixation of CO , display
the excellent catalytic behaviour for the chemical transformation
of epoxides and CO and into carbonates under mild conditions,
which further confirm that the stable octa- or nano-coordinated
state of Ln3+ ions could be viewed as the strong Lewis acid to
polarize and activate the approaching guest molecules.13 Whereas,
the catalytic performance based on the exposed heterometallic
SBUs combined from Ln3+ and Zn2+ as Lewis acidic sites is
unexplored so far.
2
, SO
2
, N
X
O
Y
, and H
2
S. Recently, the metal-organic
standard. ICP measurements were performed by
(thermofisher) iCAP Qc ICP-MS emission spectrometer.
a
2
Preparation of NUC-9
A mixture of ZnO (0.008 g, 0.1 mmol), Eu
mmol), and H PTTBA (0.057 g, 0.1 mmol) in mixed solvent of 6
mL DMF and 1 mL H O was acidified by HNO (0.2 mL,
.25mol/L) and heated in 25 mL autoclave at 110 °C for 4 days
and then gradually cooled to room temperature at a rate of 10
C/h. Colourless crystals of NUC-9 were collected by filtration
and washed by DMF/H O (3:1). (Yield: 75 % based on
PTTBA). Anal. Calcd. for NUC-9 (C41 20Eu): C,
2.89; H, 4.18; N, 6.10 (%). Found: C, 42.54; H, 4.42; N, 6.14
2 3
O (0.018 g, 0.05
2
6
2
3
0
°
2
H
6
5
H48ZnN O
Thus, based on the above mentioned discussion, our group
aimed to synthesize one heterometallic metal-organic
4
-1
(%). IR (KBr pellet, cm ): 3406 (vs), 1595 (vs), 1394 (vs), 1113
w), 1018 (w), 783 (s), 705 (w), 514 (w).
framework composed of exposed active Eu and Zn2+ ions as
strong Lewis acidic sites. Meantime, for the anticipated
applicability in the aspects of sorption and catalysis, the
targeted porous material should possess the basic intrinsic
characteristics of thermal stability, solvent-free porosity, and
high specific surface area. During the consequent
experimental process, a series of common organic ligands
were tried under the solvothermal conditions with the
adjustment of pH, temperature, the proportion of mixed
solvent. Fortunately, the acidic solvothermal reaction of ZnO,
3+
(
X-ray crystallography
The diffraction intensity data for NUC-9 was obtained at
2
96(2) K by using a Bruker Smart-APEX II CCD area detector
(
Mo-Kα radiation, 0.071073 nm) with
λ
=
graphite-monochromated radiation. The reflection data were
consequently corrected for empirical absorption corrections and
Lorentz and polarization effects. The structure w as solved by
direct methods and refined by full-matrix least-squares with the
SHELXL package. All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms except those on water molecules
were generated geometrically with fixed isotropic thermal
parameters, and included in the structure factor calculations. The
block of SQUEEZE in PLATON was employed to eliminate the
highly disordered solvent molecular. The solvent content of
NUC-9 was determined by the thermogravimetric analysis (Fig.
S1) and elemental analysis. Crystallographic data and refinement
parameter for NUC-9 were listed in Table S1. Selected bond
lengths and angles for NUC-9 were concluded in Table S2.
Further details on the crystal structure investigations may be
obtained from the Cambridge Crystallographic Data Centre, with
the depository number CCDC-2002682 for NUC-9.
Eu
carboxylic acid) (H
generated one anticipated roubst double-walled honeycomb
2
O
3
,
and 4,4′,4′′-(pyridine-2,4,6-triyl)tri(1,3-benzenedi-
6
PTTBA) in mixed solvent of DMF/H
2
O
III
II
material
of
{[Eu Zn (HPTTBA)(H
2
O)]4DMF3H
2 n
O}
(
simplified as NUC-9), in which channels were shaped by
III
II
undocumented [Eu Zn (CO
four aromatic rings as the wall. Moreover, NUC-9 could
slectively adsorb CO and effetively catalyze the the chemical
2 6 2
) (H O)] SBUs and conjugated
2
transformation of various epoxides into the related carbonates
under comparatively mild conditions. In addition, the
fluorescence sensing experiments exhibited that NUC-9 could
selectivly and sensitively discriminate Fe3+ in aqueous
solution.
Catalytic Experiment Operation
Experimental Section
Prior to the catalytic coupling reaction, the sample of NUC-9
was immersed in acetone for 24 hours and then dried in vacuum
at 120 °C for 12 hours to form the activated catalyst. During the
catalytic process, alkyl epoxides were sealed in 20 mL
around-bottom flask reactor, which was equipped with magnetic
stirrer and heated in temperature-controlled oil bath under
Materials and General Methods
All chemical reagents were commercially obtained from Jinan
Henghua Sci. & Tec. Co. Ltd. without any any further
refinement. The infrared spectrum (IR) in the range of 500-4000
cm-1 was measured on Nicolet 740 FTIR spectrometer. The
element analysis (C, H, and N) was fulfilled on the EA 1110
ambient pressure. CO
2 2
was slowly purged CO into the reactor
until the reaction was over. Finally, the product was extracted

View Article Online
DOI: 10.1039/D0DT02730H
Page 3 of 9
Dalton Transactions
with chloroform and the solid catalyst could be easily collected
by filtration. The obtained product was analysed by GC and H
NMR spectroscopy.
coordinated by one aqueous molecule and Zn2+ is linked by the
1
α-carboxyl group furthest from nitrogen atom from another one
5
-
HPTTBA (Fig. 1a and 1b). Totally, the formation of one
III
II
[
Eu Zn (CO
2 6 2
) (H O)] SBU involves six carboxyl groups offered
5
-
Result and discussion
by five HPTTBA ligands. Meantime, six deprotonated carboxyl
groups in one HPTTBA possess three types of coordination
modes: μ
5
-
Crystal structure analysis
1
1
1
0
1
1
1
-η :η , μ
1
2
-η :η , and μ -η :η .
Single-crystal X-ray analysis exhibited that NUC-9
crystallized in a rhombohedral system with R-3m space group
and possess one high-robust double-walled honeycomb host
framework with 60.2 % porosity, derived from PLATON
III
II
2 6 2
calculation. In NUC-9, each six rows of [Eu Zn (CO ) (H O)]
SBUs and half equal amount of HPTTBA5- carbon skeletons are
alternately arranged to form two classes of tubular nanochannels
along the crystallographic axis of c, both of which could be
differentiated according to the discrepant inner surface
functionalized by free carboxyl oxygen atoms or coordinated
aqueous molecules on Eu3+ ion. Moreover, except for the
excellent characteristics of dual tubular nanochannels, high
porosity, and larger specific surface area, the host framework of
NUC-9 contains high density of exposed active metal sites
including tetra-coordinated Zn2+ cations and octa-coordinated
Eu3+ cations, which are spanned together by three deprotonated
III
II
2 6 2
carboxyl groups to form [Eu Zn (CO ) (H O)] SBUs as Lewis
acidic bases, consequently realizing the functionalization of the
targeted MOFs. These embodied prominent merits render NUC-9
to be one potential multifunctional material in current hot
research fields of gas separation and storage, organic reaction
catalysis, fluorescence recognition, etc. Moreover, it is
meaningful that the structural construction mode combined from
III
II
[
2 6 2
Eu Zn (CO ) (H O)] SBUs and conjugated four aromatic rings
5
-
of HPTTBA as the wall of channels is relatively simple and the
host framework is quietly stable up to 390 °C. Meantime, the
yield of NUC-9 by the solvothermal reaction of ZnO, Eu
PTTBA at 110 °C could reach 95 %, implying the feasibility
of industrial production.
2 3
O , and
H
6
III
II
As one of highlights, the ligand-directed synthetic strategy
could be confirmed by the micro connection fashion between
metal ions and HPTTBA5- in NUC-9. Under the acidic
solvothermal condition with the equal amount of Eu3+ and Zn2+,
rare earth cation of Eu3+ was preferentially coordinated via the
chelation mode by two deprotonated α-carboxyl groups, shown in
Fig. 1b. Based on the basic knowledge of orbital binding energy
and our speculation, the reason for the priority coordination right
Fig. 1 (a) The [Eu Zn (CO
2
)
6
(H
2
O)] heterometallic cluster of NUC-9; (b)
Coordination mode of HPTTBA ligand; (c) The structural details of
channel I; (d) The structural details of channel II; (e) 3D dual-channel
framework of NUC-9; (f) 3D (5,5)-c fng topology structure with the
6
4
Schläfli symbol of {4 .6 } (yellow triangle = HPTTBA ligand and blue
polyhedron = heterometallic cluster)(c);
III
II
Moreover, as shown in Fig. 1e, [Eu Zn (CO ) (H O)] SBUs
2
6
2
are extended into one double-walled honeycomb structure, which
characterized two types of nano-channels (Fig. 1c for I and Fig.
1d for II) with slightly different aperture of 11.8 Å and 12.6 Å,
respectively. Channel I exhibits that the only free carboxyl
oxygen atoms in each HPTTBA5- stand on the surface of these
channel inner wall, which could enhance the polarity of the
nano-channel wall and consequently promote the absorption of
carbon dioxide.15a Whereas, as shown in Fig. 1d, the associated
water molecules on Eu3+ cations characterize channel II by
perpendicularly pointing to the centre of the nano-channel. Thus,
channels of I and II own the completely different functionalized
inner surface except for similar exposed metal sites and C-H
organic panel on the wall. Finally, for the purpose of visual
clarity, the host framework of NUC-9 could be simplified as a 3D
of Eu3+ ions is that the binding energies ΔE
between 4f rare
n
earth cations and coordinated oxygen atoms is larger than the one
of 3d transitional metal cations.14 Of course, in the absence of
Eu3+ ions, such two deprotonated α-carboxyl groups also could
chelate Zn2+ ion to lead to one kind of Zn-MOFs with the
relatively lower porosity of ca. 40 %. Furthermore, it is worth
mentioning that only these two α-carboxyl groups nearest to the
N atom could synergistically chelate one Eu3+ ion, which should
be attributed to that the positive charge environment devoted by
the protonated hydrogen atom on N atom affect the arrangement
of nearest carboxyl groups in one HPTTBA5- ligand from our
2 2
)
ion and one Zn2+ are
speculation. Moreover, one Eu(CO
further spanned together by three different γ-carboxyl groups
5
-
6
4
from three other HPTTBA ligands to generate the basic SBUs
(5,5)-c fng topology with the Schläfli symbol of {4 .6 } by
III
II
2 6 2
of [Eu Zn (CO ) (H
O)], in which the Eu3+ ion is further

View Article Online
DOI: 10.1039/D0DT02730H
Dalton Transactions
Page 4 of 9
III
II
O)] SBUs and HPTTBA5- ligands as
reducing [Eu Zn (CO
5
2
)
6
(H
2
a few days or soaking in boiling water for 48 h (Fig. S2). Thus,
the extremely high thermal and water stability of NUC-9 should
be ascribed to the intrinsic strong coordination affinity between
-connected nodes, shown in Fig. 1f.
In addition, it is worth mentioning that
with the aid of the designed functionalized hexacarboxyl
III
II
2 6 2
[Eu Zn (CO ) (H O)] SBUs and conjugated four aromatic rings
5
-
ligand of H
6
TDP (Scheme 1), which possesses several unique
of HPTTBA .
characters: (i) Six carboxyl groups may be completely or partially
deprotonated to devote rich coordination modes and sequentially
build highlight skeletons with nanoporous channels or cages. (ii)
The nitrogen atom of pyridine could be protonated and acts as
charge balancer, Which could effectively tolerate the generation
of special skeleton. (iii) The twist angle between central pyridyl
planar and three propagated phenyl rings at 2, 4, and 6-positon in
6
H TDP can be adjusted by itself for adaptive structure
self-assembly.
Compared to recently documented neutral framework of
[
Eu(BTB)(phen)]13b and anion of [Zn ]15b, NUC-9
2 2 4
(L)(H O)PO
not only consists of these similar exposed metal ions of
octa-coordinated Eu3+ and tetra-coordinated Zn , but also
features 1D nano-channels and the higher porosity (60.2 % for
2+
NUC-9, 42.5 % for [Zn
Eu(BTB)(phen)]), which implies that NUC-9 can more
effectively catalyze the chemical transformation of epoxides and
CO into related carbonates, especially for the ones with larger
substitutes. Moreover, it is worth making a brief discussion that
these structural characteristics of NUC-9 could provide one
productive self-assembly route for achieving anticipated
multifunctional MOFs with nano-tubular channels. Firstly, the
employment of ligands is more conducive because the triangle
plane of carbon skeleton with a certain degree of twist could be
shared by three nano-tubular channels, such as reported MOFs
2 2 4
(L)(H O)PO ], and 56.1 % for
[
2
Fig. 2 CO sorption isotherm of NUC-9 at 273 and 298 K.
Gas Adsorption Studies
2
For achieving the permanent porosity, the as-synthesized
crystalline sample of NUC-9 was activated by soaking in
methanol for three times within one week and consequently
vacuum dried at 120 °C for one overnight. The integrity of
activated NUC-9 was confirmed by the PXRD patterns, which
was in accordance with the one simulated from X-ray
single-crystal diffraction data, shown in Fig. S2. The adsorption
performance for N
2
at 77 K exhibited that the total pore volume
derived
from
1,3,5-benzenetricarboxylic
acid
and
and the calculated BET surface of activated NUC-9 were 0.52
1
6a
1
,3,5-(4-carboxylphenyl)benzene.
Secondly, in order to
3
2
cm /g and 1591 m /g, respectively. Moreover, the
adsorption-desorption isotherm of N displayed a typical type-I
enhance the heat and water resistance stability, as many
coordination groups as possible participate in coordination
without affecting the porosity and the amount of exposed active
2
sorption configuration and a very sharp uptake at P/P0<0.01,
representative of microporous material with permanent
6
metal sites, such as employed H PTTBA, which combines
microporosity, shown in Fig. S3. In addition, analysis of the N
adsorption data using the nonlocal density functional theory
NLDFT) model confirms an aperture distribution in the range of
.1−1.3 nm, which agreed with the SCXRD analysis, shown in
Fig. S3.
Due to that the innate structural advantages of tubular
nanochannels and high density of exposed active metal sites
endowed NUC-9 with the potentiality of adsorbing guest
molecules with a quadrupole moment; the affinity for CO
explored at 273K and 298 K. As shown in Fig. 2, the maximum
2
several unique characters: (i) Six carboxyl groups may be
completely or partially deprotonated to devote rich coordination
modes and sequentially build highlight skeletons with
nanoporous channels or cages. (ii) The nitrogen atom of pyridine
could be protonated and acts as charge balancer, which could
effectively tolerate the generation of special skeleton. (iii) The
twist angle between central pyridyl planar and three propagated
(
1
6
phenyl rings at 2, 4, and 6-positon in H TDP can be adjusted by
2
was
itself for adaptive structure self-assembly. Thirdly, the usage of
DMF or DEF as reaction solvent could effectively avoid the
formation of inter-crosslinked structures, may be due to the
3
3
uptake of CO
K, and meantime the obvious hysteresis loop resulted from the
sorption isotherm and incomplete desorption of CO confirmed
these strong host−guest interactions. Furthermore, in order to
quantify the binding force between CO molecules and the
framework of NUC-9, the Qst was calculated by the virial method
2
were 91.07 cm /g at 273 K and 60.88 cm /g at 298
“
template effect”.16b
2
Thermal stability and water stability
Thermogravimetric analysis (TGA) revealed that an initial
weight loss of 4.9 % was observed between 70 and 110 °C,
corresponding to the removal of lattice water molecules (Fig. S1).
In the interval of 220–300 °C, 25.3 % weight loss was observed
and in accordance with the elimination of DMF solvent. With
temperature rising, the host framework of NUC-9 could remain
stable to 390 °C, indicating its extremely thermal stability.
Meanwhile, the PXRD pattern demonstrated that there was no
structural collapse after soaking in water at room temperature for
2
-
1
with the resulted value at zero coverage being 25.8 kJmol ,
implying that the adsorbed guest molecules of CO could be
2
easily liberated and the host framework of NUC-9 could be
regenerated, shown in Fig. S4.
Catalytic Chemical Reaction of Epoxides with CO
The precondition for emerged MOFs to be one effective
heterogeneous catalyst on the chemical conversion of CO into
2
2

View Article Online
DOI: 10.1039/D0DT02730H
Page 5 of 9
Dalton Transactions
cyclic carbonates is that it could strongly polarize and activate the
substrates of epoxides and CO molecules by exposed active
metal cations embodied in the host metal-organic framework as
strong Lewis acid and weak Lewis base.
Table 1. Cycloaddition Reaction of CO with styrene oxide under various
2
conditions.a
2-(chloromethyl)oxirane, and 2-phenyloxirane with the yield over
95%. More or less, entry of 6 could demonstrate that the long
alkyl chain of 2-(phenoxymethyl)oxirane had an adverse effect
on the catalytic cycloaddition reaction, which should be ascribed
to the effect of steric hindrance. In addition, it was worth
mentioning that the catalytic performance of NUC-9 on epoxides
with large substituents was better than the documented
2
2 2
tetra-coordinated Zn-based model of [Zn (3-tpom)(L)
], 18 which
should be due to that these larger tubular channels in NUC-9
could allow relatively large molecules to enter and leave freely.
Table 2. Cycloaddition reaction of CO
NUC-9 as catalyst.
2
and various epoxides with
a
Entry
NUC-9 (mg)
n-BuNBr (mol %)
T (℃)
60
Yield (%)b
1
2
3
4
5
6
7
50
50
2.5
2.5
2.5
5
43
61
76
78
99
38
9
70
50
50
50
0
80
60
5
70
5
80
50
0
80
a
Reaction conditions: 20 mmol styrene oxide, 50 mg NUC-9 catalyst,
b
1
2
solvent free, CO (1 atm), 8 h. Checked by H NMR and GC−MS
spectroscopy with n-dodecane as the internal standard.
Impelled by advantage of solvent-free tubular nanochannels,
tangible open active sites of Eu3+ and Zn , and free carboxyl
oxygen atoms, the catalytic efficiency of activated NUC-9
sample was evaluated by the cycloaddition reaction of epoxides
2+
with CO
tetrabutylammonium (n-Bu
2
in presence of the classical co-catalyst of
NBr), from which liberated anions of
4
Br- could render the substrate of epoxides to form the
intermediate of alkyl carbonate anion by the nucleophilic attack.
In order to determine the most available temperature, co-catalyst
dosage of n-Bu
conditions with 50 mg NUC-9 and 1 atm CO
4
NBr, and reaction time, the classical solvent-free
were taken as the
2
benchmark for the transformation reaction of styrene oxide into
phenylethylene carbonate, by which the obtained various
experimental data was concluded in Table 1. The results of
entries 1-3 exhibited that the yield could be increased to 76%
with the temperature rising 80 °C for 8 hours, suggesting that the
reaction temperature had a crucial effect on the total reaction
efficiency. Furthermore, when the quantity of the cheap
a
Reaction conditions: Substrates (20 mmol), n-Bu
(1 atm), 70 °C, 8 h. b Determined by
NUC-9 catalyst (50 mg), CO
4
NBr (2.5 mol %),
2
GC/MS with n-dodecane as the internal standard.
Prior to the application in industrial production, to test the
recoverability for one emerged catalyst is the fundamental link
due to that the continuous reduction of catalyst quantity will
greatly affect the labour cost of industrial monitoring and
operation. Thus, a series of continuous amplification experiments
by the usage of 500 mg NUC-9 for the cycloaddition reaction of
co-catalyst n-Bu
0 °C for 8 hours. In order to test the synergetic catalysis, the
experiments catalyzed by single NUC-9 or n-Bu NBr were
4
NBr was doubled, the yield could reach 99% at
7
4
2
00 mmol styrene oxide were carried out at 70 °C for 8 hours,
fulfilled and the results for the yield were unsatisfactory (entries
of 6 and 7), which proved that the active open metal sites in
NUC-9 and anions of Br- possessed the different catalytic
advantages for the double-step cycloaddition reaction of epoxides
which exhibited that NUC-9 could well maintain the catalytic
efficiency for five times, shown in Fig. S5. NUC-9 sample was
recycled after five cycles of experiments and purged with
4
methanol and dichloromethane to remove n-Bu NBr and the
with CO
2
. Therefore, the optimal solvent-free reaction conditions
NBr
at 70 °C for 8 hours were used for the
adherent substrate, leaving a remaining weight of 485 mg with
the loss of 3 %. In addition, the PXRD analysis for the recycled
NUC-9 sample exhibited that the characteristic peaks were
basically fitted with the unused activated one (Fig. S2), which
proved that NUC-9 had the potential to be an alternative catalyst
of 50 mg (3 mol %) NUC-9 catalyst, 5% mol n-Bu
co-catalyst, and 1 atm CO
subsequent experiments.
In order to verify the universal catalytic applicability of
NUC-9 for the chemical fixation of CO series of
4
2
2
, a
2
for the chemical fixation of CO .
representative epoxides with different substituent and steric
hindrance under the optimized reaction conditions were fulfilled,
listed in Table 2. The obtained results intuitively exhibited that
activated NUC-9 displayed the excellent catalytic activity for the
substrates of 2-methyloxirane, 2-ethyloxirane, 2-chlorooxirane,
In view of the microstructural characteristics of NUC-9, the
tested excellent catalytic performance, and documented relevant
ratiocinations,19 the possible reaction mechanism of synergistic
catalysis was suggested, elucidated in Fig. 3. At the beginning,
the ring of epoxide was polarized and activated by the

View Article Online
DOI: 10.1039/D0DT02730H
Dalton Transactions
Page 6 of 9
electrophonic metal ions of Zn2+ and Eu3+ located on the surface
out and exhibited that typical common metal ions had no
3
+
of the inner wall of these nano-channels. Meantime, the close
significant effect on the Fe -induced luminescence response,
which revealed that NUC-9 could efficiently sense Fe3+ ions in
water solution without interference (Fig. S8). Moreover, in order
to further explore the fluorescence sensitivity of NUC-9 toward
Fe3+ ions, luminescence experiments with quantitative titration in
the range of 0-1.2 mM were launched, shown in Fig. S9.
Meantime, as illustrated in Fig. S10, the gradually reduced
fluorescent intensity along with the increased concentration of
Fe3+ ions was analyzed by the Stern−Volmer (SV) equation of
−
anion of Br liberated from n-Bu
4
NBr launched the nucleophilic
attack to the less-hindered β-carbon atom of the polarized
epoxide, generating the intermediate of 2-bromoalkoxide weakly
hanged on the Lewis-acid metal sites. Subsequently, the
instantaneous intermediate of alkylcarbonate salt was formed
along with the nucleophilic attack of 2-bromoalkoxide to the
2
carbon atom of close polarized CO molecules. Thus, the
tendentious cyclization from 2-bromoalkoxide completed the
whole reaction with the liberation of catalysts including NUC-9
−
1
I
0
/I = 1 + Ksv[M] (Ksv: the quenching effect coefficient (M ), [M]:
and n-Bu
4
NBr.
the molar concentration of the metal ions, I and I: the
0
luminescence intensities before and after reaction with metal
ions), which displayed that the S-V curve shifted away from the
linearity with the concentration of Fe3+ ions rising and switched
3
+
to be well fitted by the equation of I
-
0
/I = 1.545×exp([Fe ]/0.044)
2
0.667 (R = 0.994). In addition, as shown in Fig. S11, the results
by fitting the experimental database of low concentration range
of Fe3+ shown that NUC-9 possessed the relatively high Ksv value
4
−1
of 4.21 × 10 M , which could be explained by self-absorption
or energy-transfer process.20 Moreover, judged by the Ksv value
and the standard deviation (δ), the detection minimum limit to
Fe3+ cations could reach 0.1 μM (7.1 ppb) according to the 3δ
IUPAC criteria.
2
Fig. 3 The catalytic mechanism cycloaddition of epoxides with CO .
Luminescence characteristic and sensing property
The solid-state luminescence spectra of H
NUC-9 excited at 320 nm at room temperature were tested and
illustrated in Fig. S6. As for H PTTBA, the strong emission peak
6
PTTBA ligand and
6
at 450 nm should be ascribed to the intraligand π* → π electronic
transitions among four conjugated aromatic rings. Whereas, for
NUC-9, five evident characteristic peaks located at 583, 596, 620,
6
57, and 707 nm in the visible region were in accordance with
5
7F
(J = 0, 1, 2, 3, and 4) transitions of Eu3+ ions,
these D
0
→
J
3
+
among which the strongest one at 620 nm confirmed that Eu
Fig. 4 Emission intensity NUC-9 aqueous suspensions with different
ions possessed the asymmetric coordination modes. Moreover, by
metal ions.
monitoring the emission at 320 nm, the solid-state PL lifetime of
Based on the structural characteristics of NUC-9 and related
documented studies on fluorescence recognition by MOFs,21 the
possible luminescence sensing mechanism toward Fe3+ ions were
deduced. Just as shown in Fig. S2, although major peaks of the
powder X-ray diffraction on the recycled NUC-9 could coincide
with the ones of the original sample, several emerged weak peaks
should be ascribed to the affinity between Fe3+ ions and the host
framework of NUC-9. In addition, the ICP results revealed that
no Eu3+ ions were detected in the NUC-9@Eu3+ suspension after
luminescence experiments, implying that the fluorescence
quenching was not caused by ion exchange (Table S3). Further
UV-visible absorption spectra of Fe3+ and the excitation spectra
of NUC-9 displayed a large overlap, indicating that the
5D
(Eu ) was determined to be 0.81 ms, shown in Fig. S7.
3+
0
Furthermore, the absolute PL quantum yield (QY) of NUC-9
with the value of 16.1 % confirmed that organic ligands of
5
-
3+
HPTTBA and Zn(II) cations could synergistically sensitize Eu
emitters.
In view of uncoordinated carboxyl oxygen atoms and pyridine
devoted HPTTBA5- ligand in NUC-9, the luminescence sensing
experiments were fulfilled towards various metal cations by the
followed approaches: equimolar amount of selected 15 typical
metal cations was separately dissolved in pre-ultrasonic 3 mL
aqueous solution with 2 mg milled sample of NUC-9 to form
n+
+
+
+
2+
2+
2+
2+
2+
M @NUC-9 (M = Li , Na , K , Mg , Ca , Ba , Mn , Zn ,
2
+
2+
2+
2+
2+
2+
3+
3+
3+
3+
Cd , Fe , Hg , Co , Ni , Cu , Al , Cr , and Fe ) aqueous
suspension, based on which the luminescence emission intensity
at 620 nm were summarized in Fig. 4. Evidently, only the
solution introduced with 1.2 mM Fe3+ was almost completely
luminescence quenched with the efficiency of 98.7%.
competitive absorption existed between Fe and the framework
3
+
of NUC-9 (Fig. S12), generating one Fe @NUC-9 intermediate
in aqueous solution along with a decline of luminescence
3+
intensity of Eu -based chromophores due to the reduction of
energy transfer efficiency from HPTTBA ligands to the Eu3+ ion.
3
+
Consequently, a series of competitive experiments for Fe ions
with the equimolar amount of other 14 metal cations were carried
Conclusions

View Article Online
DOI: 10.1039/D0DT02730H
Page 7 of 9
Dalton Transactions
Comm., 2020, 11, 497; d) S. Luo, Z. Zeng, G. Zeng, Z. Liu, R. Xiao, P.
Xu, H. W., D. Huang, Y. Liu, B. Shao, Q. Liang, D. Wang, Q. He, L. Qin,
Y. Fu, J. Mater. Chem. A, 2020, 8, 6434; e) L. Shi, Z. Li, L. Ju, A.
Carrasco-Pena, N. Orlovskaya, H. Zhou, Y. Yang, J. Mater. Chem. A,
By utilizing the ligand-directed synthetic strategy, the
solvothermal self-assembly of Zn and Eu3+ ions with the aid of
2+
the pre-designed H PTTBA generated one robust double-walled
6
honeycomb material of NUC-9, which exhibited the excellent
catalytic performance for the chemical transformation of various
epoxides into the related carbonates under comparatively mild
conditions of 1 atm CO flow and 70 °C. Meantime, the
2
water-resistant framework of NUC-9 could selectively and
sensitively discriminate Fe3+ ions in aqueous solution. In fact,
NUC-9 represented one class of emerged heterometallic
nanoporous materials based on heterometallic binuclear SBUs.
Such materials not only featured the characteristics of dual
tubular nanochannels, high porosity and specific surface area, but
also possessed tetra-coordinated transition metal ions and
octa-coordinated rare earth ions. Although ions of Zn2+ and Eu3+
2
020, 8, 1059.
5
. a) Z. Ma, P. Li, L. Ye, Y. Zhou, F. Su, C. Ding, H. Xie, Y. Bai, P. K.
Wong, J. Mater. Chem. A, 2017, 5, 24995; b) S. Luo, X. Li, M. Wang, X.
Zhang, W. Gao, S. Su, G. Liu, M. Luo, J. Mater. Chem. A, 2020, 8, 5647;
c) L. Sun, Y. Yun, H. Sheng, Y. Du, Y. Ding, P. Wu, P. Li, M. Zhu, J.
Mater. Chem. A, 2018, 6, 15371.
6
. a) Y. Sun, X. Jia, H. Huang, X. Guo, Z. Qiao, C. Zhong, J. Mater.
Chem. A, 2020, 8, 3180; b) R. Babu, R. Roshan, Y. Gim, Y. H. Jang, J. F.
Kurisingal, D. W. Kim, D.-W. Park, J. Mater. Chem. A, 2017, 5, 15961;
c) L. Huang, B. Li, B. Su, Z. Xiong, C. Zhang, Y. Hou, Z. Ding, S. Wang,
J. Mater. Chem. A, 2020, 8, 7177; d) X. L. Lv, L. H. Xie, B. Wang, M.
Zhao, Y. Cui, J. R. Li, J. Mater. Chem. C, 2018, 6, 10628.
7. a) F. Schönfeld, L. V. Meyer, F. Mühlbach, S. H. Zottnick, K.
Müller-Buschbaum, J. Mater. Chem. C, 2018, 6, 2588; b) A. Yousaf, A.
M. Arif, N. Xu, J. Zhou, C. Y. Sun, X. L. Wang, Z.-M. Su, J. Mater.
Chem. C, 2019, 7, 8861; c) H. Li, Q. Li, Z. Xu, J. Mater. Chem. C, 2019,
were selected to construct the targeted model for the catalytic
study on the chemical fixation of CO
combinations from any transition metal ions and octa-coordinated
rare earth ions with the aid of H PTTBA also could be assembled
2
by our group, other
7
, 2880; d) C. Li, W. Yang, X. Zhang, Y. Han, W. Tang, T. Yue, Z. Li, J.
6
Mater. Chem. C, 2020, 8, 2054; e) F. Y. Yi, S. C. Wang, M. Gu, J. Q.
Zheng, L. Han, J. Mater. Chem. C, 2018, 6, 2010.
for other specific functional researches in the future, such as
optics, magnetism, and so on.
8
. Y. H. Luo, A. D. Xie, W. C. Chen, D. Shen, D. E. Zhang, Z. W. Tong,
C. S. Lee, J. Mater. Chem. C, 2019, 7, 14897.
Conflicts of interest
9. a) Y. X. Zhang, B. X. Li, H. Lin, Z. Ma, X. T. Wu, Q. L. Zhu, J.
Mater. Chem. C, 2019, 7, 6217; b) J. M. Liu, J. X. Hou, J. Liu, X. Jing, L.
J. Li, J. L. Du, J. Mater. Chem. C, 2019, 7, 11851.
The authors have no conflicts of interest to declare.
Acknowledgements
1
8
0. a) A. M. Kaczmarek, P. V. D. Voort, J. Mater. Chem. C, 2019, 7,
109; b) S. Basu, S. Bhandari, U. N. Pan, A. Paul, A. Chattopadhyay, J.
The work was supported by financial support from the Natural
Science Foundation of China (21101097, 21801230), the
Opening Foundation of Key Laboratory of Laser & Infrared
System of Shandong University (2019-LISKFJJ-005), and the
start-up funds of North University of China.
Mater. Chem. C, 2018, 6, 8205.
1. a) S. Jensen, K. Tan, W. Lustig, D. Kilin, J. Li, Y. J. Chabal, T.
1
Thonhauser, J. Mater. Chem. C, 2019, 7, 2625; b) E. L. Zhou, C. Qin, D.
Tian, X. L. Wang, B. X. Yang, L. Huang, K. Z. Shao, Z. M. Su, J. Mater.
Chem. C, 2018, 6, 7874; c) E. Angioni, R. J. Marshall, N. J. Findlay, J.
Bruckbauer, B. Breig, D. J. Wallis, R. W. Martin, R. S. Forgan, P. J.
Skabara, J. Mater. Chem. C, 2019, 7, 2394; d) Y. Cheng, Y. Gao, H. Lin,
F. Huang, Y. Wang, J. Mater. Chem. C, 2018, 6, 7462.
References
1
2. Y. J. Ma, S. D. Han, J. Pan, Y. Mu, J. H. Li, G. M. Wang, J. Mater.
Chem. C, 2018, 6, 9341.
3. a) W. P. Lustig, S. J. Teat, J. Li, J. Mater. Chem. C, 2019, 7, 14739;
b) H. Xu, B. Zhai, C. S Cao, B. Zhao, Inorg. Chem. 2016, 55, 9671.
1
. a) S. A. Montzka, E. J. Dlugokencky, J. H. Butler, Nature, 2011, 476,
4
3; b) J. D. Shakun, P. U. Clark, F. He, S. A. Marcott, A. C. Mix, Z. Y.
1
Liu, B. Otto-Bliesner, A. Schmittner, E. Bard, Nature, 2012, 484, 49; c)
P. Lanzafame, G. Centi, S. Perathoner, Chem. Soc. Rev., 2014, 43, 7562;
d) Y. Wang, J. Ding, Y. Wang, X. Zhou, Y. Cao, B. Ma, J. Li, X. Wang,
T. Seto, Z. Zhao, J. Mater. Chem. C, 2019, 7, 1792; e) T. Yuan, T. Meng,
P. He, Y. Shi, Y. Li, X. Li, L. Fan, S. Yang, J. Mater. Chem. C, 2019, 7,
1
1
4. J. Sun, P. Guo, M. Liu, H. Li, J. Mater. Chem. C, 2019, 7, 8992.
5. a) L. Zhai, Z. X. Yang, W. W. Zhang, J. L. Zuo, X. M. Ren, J. Mater.
Chem. C, 2018, 6, 7030; b) M. Gupta, D. De, K. Tomar, P. K. Bharadwaj,
Inorg. Chem. 2017, 56, 14605.
6
820; f) V. Amoli, S. Y. Kim, J. S. Kim, H. Choi, J. Koo, D. H. Kim, J.
1
2
5
6. a) A. Schoedel, M. Li, D. Li, M. O’Keeffe, O. M. Yaghi, Chem. Rev.
016, 116, 12466; b) Y. J. Li, Y. L. Wang, Q. Y. Liu, Inorg. Chem. 2017,
6, 2159.
Mater. Chem. C, 2019, 7, 14816; g) S. Zhao, R. Jin, ACS energy Lett,
2
018, 3, 425.
2
. a) A. Goeppert, M. Czaun, G. K. Surya Prakash, G. A. Olah, Energy
17. a) X. P. Wang, W. M. Chen, X. Y. ,Li, Rajnák. Cyril, D .Sun. Chem.
Eur. J. 2017, 23, 7990; b) W. M. Chen, X. L. Meng, G. L. Zhuang, Z.
Wang, M. Kurmoo, Q. Q. Zhao, X. P. Wang, B. Shan, C. H. Tung, D.
Sun. J. Mater. Chem. A. 2017, 5, 13079; c) D. Sun, G. G. Luo, N. Zhang,
J. H. Chen, R. B. Huang, L. R. Lin, L. S. Zheng.
polyhedron, 2009, 28, 2983; d) D. Sun, Z. H. Yan, M. Liu, H. Xie, S.
Yuan, H. Lu, S. Feng, D. Sun. Cryst. Growth Des. 2012, 12, 2902; e) L. L.
Han, T. P. Hu, K. Mei, Z. M. Guo, C. Yin, Y. X. Wang, J. Zheng, X. P.
Wang, D. Sun. Dalton Trans. 2015, 44, 6052.
Environ. Sci., 2012, 5, 7833; b) H. Wang, Z. Zhang, H. Wang, L. Guo, L.
Li, Dalton Trans. 2019, 48, 15970; c) E. S. Sanz-Pérez, C. R. Murdock,
S. A. Didas, C. W. Jones, Chem. Rev., 2016, 116, 11840; d) M. Z.
Jacobson, Energy Environ. Sci., 2009, 2, 148; e) D. M. Fernandes, A. F.
Peixoto, C. Freire, Dalton Trans. 2019, 48, 13508.
3
. a) C. Li, X. Tong, P. Yu, W. Du, J. Wu, H. Rao, Z. M. Wang, J. Mater.
Chem. A, 2019, 7, 16622; b) Y. Wu, X. Song, S. Xu, Y. Chen, O.
Oderinde, L. Gao, R. Wei, G. Xiao, Dalton Trans. 2020, 49, 312.; c) J.
Zhu, J. Liu, Y. Machain, B. Bonnett, S. Lin, M. Cai, M. C. Kessinger, P.
M. Usov, W. Xu, S. D. Senanayake, D. Troya, A. R. Esker, A. J. Morris,
J. Mater. Chem. A, 2018, 6, 22195; d) M. Wang, W. Zhong, S. Zhang, R.
Liu, J. Xing, G. Zhang, J. Mater. Chem. A, 2018, 6, 9915; e) D. Ma, B.
Li, K. Liu, X. Zhang, W. Zou, Y. Yang, G. Li, Z. Shi, S. Feng, J. Mater.
Chem. A, 2015, 3, 23136.
1
1
8. V. Gupta, S. K. Mandal, Inorg. Chem. 2020, 59, 4273.
9. a) Z. F. Wu, E. Velasco, C. Shan, K. Tan, Z. Z. Zhang, Q.-Q. Hu, K.
Xing, X. Y. Huang, J. Li, J. Mater. Chem. C, 2020,
https://doi.org/10.1039/D0TC00825G; b) D. Jiang, X. Yang, X. Zheng, L.
Bo, T. Zhu, H. Chen, L. Zhang, S. Huang, J. Mater. Chem. C, 2018, 6,
8
2
513.
0. a) B. C. Tzen, J. F. Lin, Dalton Trans. 2020,
4
. a) S. Wang, K. Song, C. Zhang, Y. Shu, T. Li, B. Tan, J. Mater. Chem.
https://doi.org/10.1039/C8DT04904A; b) D. Xu, L. Chen, X. Dai, B. Li,
Y. Wang, W. Liu, J. Li, Y. Tao, Y. Wang, Y. Liu, G. Peng, R. Zhou, Z.
Chai, S. Wang, ACS Sustainable Chem. Eng. 2020, 12, 15288; c) W. Chi,
A, 2017, 5, 1509; b) F. Guo, X. Zhang, Dalton Trans. 2020, 49, 9935; c)
S. Li, L. Zhang, Y. Lan, K. P. O’Halloran, H. Ma, H. Pang, Nature

View Article Online
DOI: 10.1039/D0DT02730H
Dalton Transactions
Page 8 of 9
J. Chen, W. Liu, C. Wang, Q. Qi, Q. Qiao, T. M. Tan, K. Xiong, X. Liu,
K. Kang, Y. T. Chang, Z. Xu, X. Liu, J. Am. Chem. Soc. 2020, 142, 6777;
d) C. Y. Liu, X. R. Chen, H. X. Chen, Z. Niu, H. Hirao, P. Braunstein,
J.-P. Lang, J. Am. Chem. Soc. 2020, 142, 6690; e) T. Y. Li, D. S. M.
Ravinson, R. Haiges, P. I. Djurovich, M. E. Thompson, J. Am. Chem.
Soc. 2020, 142, 6158; f) B. Liu, M. Böckmann, W. Jiang, N. L. Doltsinis,
Z. Wang, J. Am. Chem. Soc. 2020, 142, 7092; g) X. Hei, W. Liu, K. Zhu,
S. J. Teat, S. Jensen, M. Li, D. M. O’Carroll, K. Wei, K. Tan, M. Cotlet,
T. Thonhauser, J. Li, J. Am. Chem. Soc. 2020, 142, 4242.
W. Shen, C. I. Wu, G. Xie, J. Zhou, Z. X. Huang, C. Y. Huang, S. J. Su,
W. Zhu, P. T. Chou, J. Am. Chem. Soc. 2020, 142, 7469; c) Y. X. Hu, X.
Hao, L. Xu, X. Xie, B. Xiong, Z. Hu, H. Sun, G. Q. Yin, X. Li, H. Peng,
H.-B. Yang, J. Am. Chem. Soc. 2020, 142, 6285; d) Y. L. Wang, C. Li, H.
Q. Qu, C. Fan, P. J. Zhao, R. Tian, M. Q. Zhu, J. Am. Chem. Soc. 2020,
142, 7497; e) Yang, O. Jacobson, F. Zhang, P. Huang, X. Chen, J. Am.
Chem. Soc. 2020, 142, 6822; f) S. Yuan, L. Huang, Z. Huang, D. Sun, J.
S. Qin, L. Feng, J. Li, X. Zou, T. Cagin, H. C. Zhou, J. Am. Chem. Soc.
2020, 142, 4732.
2
1. a) X. Hu, L. Zhong, C. Shu, Z. Fang, M. Yang, J. Li, D. Yu, J. Am.
Chem. Soc. 2020, 142, 4621; b) X. Wu, D. G. Chen, D. Liu, S. H. Liu, S.

View Article Online
DOI: 10.1039/D0DT02730H
Page 9 of 9
Dalton Transactions
Graphical Abstract
III
II
One robust double-walled honeycomb material of {[Eu Zn (HPTTBA)(H
2
O)]4DMF3H
2
O}
n
with excellent catalytic performance on
the chemical fixation of CO was presented by utilizing the ligand-directed synthetic strategy.
2