Four congenetic zinc(II) MOFs from delicate solvent-regulated strategy: Structural diversities and fluorescent properties

Article abstract of DOI:10.1016/j.ica.2019.119296

Four new congenetic zinc(II) MOFs, namely [Zn₅(bdcpp)₃(DMF)(H₂O)₄]_n·x(solvent) (1), [Zn₂(bdcpp)(Hbdcpp)]_n·y(solvent) (2), [Zn₂(bdcpp)(DMF)(H₂O)₂]

Full text of DOI:10.1016/j.ica.2019.119296

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Research paper
Four congenetic zinc(II) MOFs from delicate solvent-regulated strategy: struc-
tural diversities and fluorescent properties
Gui-Lin Wen, Bo Liu, Dao-Fu Liu, Feng-Wu Wang, Li Li, Liang Zhu, Dong-
Mei Song, Chao-Xiu Huang, Yao-Yu Wang
PII:
S0020-1693(19)31302-7
https://doi.org/10.1016/j.ica.2019.119296
ICA 119296
DOI:
Reference:
Inorganica Chimica Acta
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30 August 2019
20 November 2019
20 November 2019
Please cite this article as: G-L. Wen, B. Liu, D-F. Liu, F-W. Wang, L. Li, L. Zhu, D-M. Song, C-X. Huang, Y-Y.
Wang, Four congenetic zinc(II) MOFs from delicate solvent-regulated strategy: structural diversities and fluorescent
properties, Inorganica Chimica Acta (2019), doi: https://doi.org/10.1016/j.ica.2019.119296
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Four congenetic zinc(II) MOFs from delicate solvent-regulated
strategy: structural diversities and fluorescent properties
Gui-Lin Wena,*, Bo Liub,*, Dao-Fu Liu a Feng-Wu Wang a, Li Li a, Liang Zhu a, Dong-Mei Song a,
,
Chao-Xiu Huang a, Yao-Yu Wangc
a School of Chemistry and Materials Engineering, Huainan Engineering Research Center for Fuel Cells, Anhui
Province Key Laboratory of Low Temperature Co-fired Materials, Huainan Normal University, Huainan 232038,
China
b College of Chemistry & Pharmacy, Northwest A&F University, Yangling 712100, China
c Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, Shaanxi
Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry &Materials Science, Northwest University,
Xi'an 710069, China
ABSTRACT: Four new congenetic zinc(II) MOFs, namely [Zn5(bdcpp)3(DMF)(H2O)4]n·x(solvent)
(1),
[Zn2(bdcpp)(Hbdcpp)]n·y(solvent)
(2),
[Zn2(bdcpp)(DMF)(H2O)2]n
(3),
and
[Zn2(bdcpp)(NMP)(H2O)2]n (4) (H4bdcpp = 2,6-bis(2',4'-dicarboxylphenyl)pyridine, DMF =
N,N'-dimethyl formamide, NMP = N-methyl-2-pyrrolidone), have been synthesized solvothermally
with different solvent systems. Stabilized by Zn2(COO)4 paddle-wheel building blocks, the resulting
MOFs 1–4 represent diverse structural features. Structurally, 1 is a rarely 3,4-c binodal 2D bilayered
framework, 2 possesses a 4-c 2D (4,4) sql planar network accommodating two kinds of hetero chiral
helix chains, 3 and 4 are iso-structural 1D loop ladder chains except different solvent molecules
occupying the axial terminals of Zn2(COO)4 paddle-wheels. This approach based on
solvent-regulated strategy aiming to allow the structural fine-tuning provides a good role model in
reticular chemistry. Complexes 1−3 display excellent solid-state photoluminescence stemming from
the metal-to-ligand charge transfer or intraligand charge transmission.
Keywords: Solvent-regulated strategy, Zn(II)-MOFs, Congenetic synthesis, Structural diversities,
Fluorescent properties
*Corresponding authors. Tel./fax: +86-554-6672650, +86- 29-87092662.
E-mail address: guilinwen@126.com (G.-L. Wen), chemliubo@nwsuaf.edu.cn (B. Liu)

1. Introduction
Over the past two decades, metal-organic frameworks (MOFs) assembled by metal / metal
clusters and organic ligands have attracted tremendous attention in the field of chemistry and
materials science [1]. The regular highly-ordered structures of MOFs endow these crystalline
functional materials potential applications in gas storage, separation, sensing, catalysis, photoelectric
materials and so on [2]. The rapid development of MOFs benefits basically from the diversity and
designability of metal nodes and linking blocks, which provides more options for the construction of
MOFs owning fascinating frameworks and attractive functions [3]. It is apparently that some external
factors may also have a positive impact on the synthesis trend and process, such as solvent (volume
ratio, polarity, aprotic / protic), pH value, template, crystal seeds and cooling rate [4]. The ultimate
aim of reticular chemistry is to achieve controllable molecular self-assembly of the solid materials
[5]. What inspiring us is that some examples of the rational design of MOFs have already been
achieved based on the design of metal containing SBUs and organic linkers in the unremitting efforts.
Nevertheless, that is far from achieving the final expected results [4,5].
Solvent system has the characteristics of the widespread source, low cost and highly
maneuverable. It means that the precise selection of the solvent is essential to the synthesis of final
product [6]. Solvent system could perform different roles in the reaction process except for
dissolving the raw materials to get crystalline MOFs: (i) participating in the reaction as ligands; (ii)
filling the pores as guest molecules; (iii) dual roles with host bonding and guest adsorption; (iv)
structure-director as a template [7]. In other words, the solvent does not only act as a carrier for
chemical reaction, but also enhances the stability of the whole framework and even expands the
variety of crystalline substances. According to the literatures, some researches on solvent effects for
syntheses of MOFs are reported. However, the number of the MOF structures obtained from a
solvent-based synthesis system are only in small numbers and even rarely more than three cases
[7c,8]. Therefore, it is still desirable to explore new systems systematically to construct the MOFs in
greater numbers and make clear the synthetic mechanisms.
It has been reported that the designing or modification of the ligands to obtain new MOFs in
solvent-regulated strategies was feasible. Especially, owing to holding both hydrophobic molecular
skeleton and two or more hydrophilic carboxylic groups, the aromatic polycarboxylates were given

innately the ability of the subtle control of solvent action, which was logically excellent research
objectives to investigate the syntheses of solvent-regulated MOFs [8,9]. Aromatic polycarboxylates
show comparable stability, diverse coordination ability, and adjustable deprotonation degree of
carboxylic groups, which affords a stage for the solvent system to determine the structure type of
MOFs
like
a
marionette
[9c,10].
Accordingly,
we
target
V-shaped
2,6-bis(2',4'-dicarboxylphenyl)pyridine (H4bdcpp), possessing embedded pyridyl acting as Lewis
basic sites and two neighboring 2-carboxyls being favorable for the forming of M2(COO)4
paddle-wheels SBUs, which is very efficient for MOFs construction as functional building blocks.
To date, just one case tethering the H4bdcpp ligand has been documented with a
surfactant-introduction strategy for separating two pure MOFs [11]. In this context, four congenetic
zinc(II)-based
MOFs
of
(2)
[Zn5(bdcpp)3(DMF)(H2O)4]n·x(solvent)
[Zn2(bdcpp)(DMF)(H2O)2]n
(1),
[Zn2(bdcpp)(Hbdcpp)]n·y(solvent)
，
(3)
and
[Zn2(bdcpp)(NMP)(H2O)2]n (4) were successfully synthesized through the solvent-regulated strategy.
The assembly of the precursors was deeply influenced by the solvent types and ingredients, and the
products of MOFs 1-4 exhibit multifarious structural features. In addition, the physio-chemical
properties were evaluated using FT-IR, TGA, PXRD and fluorescence spectrophotometer.
2. Experimental
2.1. Chemicals and physical measurements
All reagents and solvents were purchased commercially and used as received. FT-IR spectra
(KBr pellets) were recorded in the 400-4000 cm−1 region with a Nicolet Avatar360 FT-IR
spectrometer. Thermogravimetric analyses (TGA) were performed on a METTLER-TOLEDO
TGA/STDA 851e Thermal Analysis at a heating rate of 10 °C/min under the protection of N2 stream.
Powder X-ray diffraction (PXRD) patterns were carried out in a Bruker D8 ADVANCE X-ray
powder diffractometer (Cu-Kα, 1.5418 Å). Photoluminescent spectra were investigated with a
Hitachi F-7000 Fluorescence Spectrophotometer.
2.2. Synthesis of 2,6-bis(2',4'-dicarboxylphenyl)pyridine
The synthesis technique of H4bdcpp is similar to 3,5-di(2′,4′-dicarboxylphenyl)benozoic acid
[12]. The synthesis procedure of H4bdcpp is shown stepwise in Scheme 1.

Scheme 1. The scheme for the synthesis of 2,6-bis(2',4'-dicarboxylphenyl)pyridine (H4bdcpp). Reaction conditions:
(i) 4-bromoisophthalic acid (0.05 mol, 12.3 g), ethanol (250 mL), concentrated H2SO4 (5 mL), refluxing for 10 h;
(ii) diethyl 4-bromoisophthalate (0.05 mol, 15.0 g), bis(pinacolato)diborane (0.025 mol, 6.4 g), CH3COOK (0.15
mol, 14.7 g), dried 1,4-dioxane (250 mL), Pd(dppf)2Cl2 (7.0 mmol, 5.1 g), refluxing overnight, extracting thrice
with ethyl acetate (150 mL) after pouring into H2O (2000 mL), recrystallizing; (iii) (1)
4,4,5,5-tetramethyl-2-(diethyl-2,4-dicarboxylatephenyl)-1,3-dioxolane (0.05 mol, 17.40 g), 2,6-dibromopyridine
(0.025 mol, 5.9 g), K3PO4 (0.1 mol, 21.2 g), 1,4-dioxane (250 mL), deaerating with N2 for 20 min; (2) Pd(PPh3)4
(0.5 mmol, 0.6 g), refluxing for 6 d, recrystallizing; (iv) (1) tetraethyl 2,6-bis(2,4-dicarboxylphenyl)pyridine (0.05
mol, 26.0 g), NaOH (8 g), H2O (500 mL), refluxing for 2 h; (2) neutralizing with concentrated HCl.
2.3. Synthesis of [Zn5(bdcpp)3(DMF)(H2O)4]n·x(solvent) (1)
A mixture of H4bdcpp (0.1 mmol, 0.0410 g), ZnSO4·7H2O (0.2 mmol, 0.0575g), and 0.05 mL
HNO3 (63%, aq.) in the solvent system of DMF (3.5 mL) / distilled water (1.5 mL) was introduced
into a 25 mL Teflon-lined autoclaved stainless steel vessel, heated at 105 °C for 48 h, and then
cooled naturally to room temperature. Colorless block crystals of 1 were obtained in 59% yield based
on H4bdcpp ligand. IR spectrum (cm-1, KBr pellet):3778w, 3408s, 2796m,2487m,1656s, 1625s,
1438m, 1373s, 1254m, 1172w, 1102w, 1023w, 818w, 784m, 734w, 697m, 567w, 481w.
2.4. Synthesis of [Zn2(bdcpp)(Hbdcpp)]n·y(solvent) (2)
The same procedure as that of 1 was used except that solvent system was replaced by 5 mL
DMF and 0.2 mL H2O for 2. Colorless block crystals of 2 were obtained in 49% yield based on

H4bdcpp ligand. IR spectrum (cm-1, KBr pellet): 3404s, 3068m, 2790m, 2486w, 2359s, 1654s,
14387m, 1369s, 1253m, 1174w, 1102w, 1023w, 923w, 818m, 781m, 731w, 697m, 569w, 483m.
2.5. Synthesis of [Zn2(bdcpp)(DMF)(H2O)2]n (3)
H4bdcpp (0.1 mmol, 0.041 g), ZnSO4·7H2O (0.2 mmol, 0.0575 g), DMF (5 mL) and 0.05 mL
HNO3 (63%, aq.) were mixed uniformly and then sealed in a 25 mL Teflon-lined autoclaved stainless
steel vessel. After being heated at 105 °C for 48 h, the mixture was cooled naturally to room
temperature. Colorless block crystals of 3 were collected with 55% yield based on H4bdcpp ligand.
IR spectrum (cm-1, KBr pellet): 3430s, 2934m, 2358w, 1666s, 1497m, 1437s, 1379s, 1253m, 1171w,
1103s, 1062w, 819m, 788s, 734m, 667m, 568w, 485m.
2.6. Synthesis of [Zn2(bdcpp)(NMP)(H2O)2]n (4)
The synthetic procedure was similar to that of 3 except that 5 mL DMF was changed into the
mixed DMF/NMP system (2.5 mL /2.5 mL). Very little colorless block crystals of 4 were obtained.
2.7. X-ray crystallographic Studies
The crystal data for complexes 1–4 were collected at room temperature with a Bruker APEX
IISMART CCD area detector diffractometer with graphite-monochromated Mo-Kα radiation (λ =
0.71073 Å). The structures were solved by direct method using SHELXS-97, and then refined with
full matrix least-square methods based on F2 with SHELXL-97 [13]. The SQUEEZE program was
applied to remove the scattering from the highly disordered guest solvent molecules and anion ions
in the frameworks of complexes 1 and 2. All hydrogen atoms except the coordinated water molecules
were fixed theoretically, and the aqua hydrogen atoms were located from differential Fourier maps.
Metal atoms Zn2, Zn3 and Zn4 of complex 1 situate special coordinate positions. The disordered
methyl groups of DMF and coordinate water O1W and O2W in 1 are dealt with equal site
occupancies into two positions. CCDC 1535086–1535089 for 1–4 contain the supplementary
crystallographic data for this paper. The crystal data and refinement details for 1–4 are listed in
Table 1. Selected bond lengths and bond angles of 1–4 are summarized in Table S1.

Table 1. Crystallographic data and structure refinement details for 1–4
Complex
1
2
3
4
Empirical formula
M
C66H42N4O29Zn5
1681.89
Monoclinic
C2/m
C42H19N2O16Zn2
938.33
C24H20N2O11Zn2
643.16
C26H22N2O11Zn2
669.20
Crystal system
Space group
a [Å]
Triclinic
Pī
Monoclinic
C2/c
Monoclinic
C2/c
22.888(4)
25.631(4)
16.944(3)
90
13.707(6)
14.229(6)
15.229(7)
95.789(7)
106.877(7)
90.060(7)
2826(2) / 2
1.103
28.917(14)
16.436(8)
19.031(9)
90
29.593(9)
16.576(5)
18.963(6)
90
b [Å]
c [Å]
α [˚]
β [˚]
102.728(3)
90
118.713(6)
90
120.983(5)
90
γ [˚]
V [Å3] / Z
dcalcd[g·cm–3]
μ [mm–1]
9696(3) / 4
1.152
7933(7) / 8
1.077
7975(4) / 8
1.115
1.283
0.904
1.251
1.247
F(000)
3392
946
2608
2720
θ Range [°]
Reflections collected
R(int)
1.21–28.47
34739
1.41–26.02
16879
1.48–25.68
19187
1.47–25.38
19366
0.0874
0.0542
0.0797
0.1029
Goodness-of-fit on F2
R1[a], wR2[b] [I>2σ(I) ]
R1[a], wR2[b] [all data]
1.031
1.158
1.190
1.025
0.0762, 0.1865
0.1300, 0.2072
0.0915,0.2143
0.0938, 0.2466
0.1561, 0.2649
0.0839, 0.2139
0.1437, 0.2335
0.1093,0.2216
2
2
[a] R 1= Σ||Fo|–|Fc||/Σ|Fo|; [b] wR2 = [Σw(Fo – Fc2)2/Σw(Fo ) 2]1/2
3. Results and discussions
3.1. Syntheses
The aromatic polycarboxylate 2,6-bis(2',4'-dicarboxylphenyl)pyridine and ZnSO4·7H2O were
used as precursor reagents in the synthetic process, and a lot of exploratory experiments have been
made carefully to obtain the desired MOFs crystals (see Fig. 1). Direct mixing treatment of the
organic materials and zinc salts in aqueous solution generates plenty of fine precipitates immediately,
so the hydro(solvo)thermal techniques were applied to produce suitable crystals for X-ray analysis.
Complexes 1–4 have been synthesized successfully under the same reaction conditions except for

different solvent systems. Using DMF / H2O (7:3, v/v) as solvent led to the regular block crystals of
1, while reducing water amount to several drops made for the block crystals of 2. For 3 and 4, DMF
and DMF / NMP (1:1, v/v) served as the solvent systems, respectively. But unfortunately, the yield
of 4 is too low despite various attempts. Although the experiments with the other solvent systems
have also been carried out, only unknown deposits were obtained. Little additional concentrated
acids in solvothermal system should contribute to the deprotonation decelerating of the carboxylic
acids, which facilitates the formation of MOFs materials with high quality.
Fig. 1. Synthetic procedures of complexes 1–4.
3.2. Description of crystal structures
3.2.1. Crystal structure of complex 1
Single-crystal X-ray diffraction measurements show that complex 1 crystallizes in the
monoclinic C2/m space group. The 2D zinc-based anionic MOF accommodates two kinds of
dinuclear Zn2(COO)4 paddle-wheel units and one metal center, in which unknown cations might be
inclosed presumably into the interlayers to balance the global charge of anionic framework. As
revealed in Fig. 2a, there are two and half Zn2+ ions, one and half deprotonized bdcpp4- ligands, half

DMF molecule, two coordinated water in the asymmetric unit. Zn1 ion is four-coordinated by three
carboxylic O atoms from three bdcpp4- ligands and one O atom from a water molecule. The
coordination geometry of Zn1 can be described as a tetrahedral mode without regard to the elongated
Zn1–O10 bond of 2.614(4) Å. The Zn2, Zn3 and Zn4 ions are coordinated with tetragonal pyramidal
geometry affording different Zn2(COO)4 paddle-wheels, which two DMF molecule located at the
axial sites in one paddle-wheel from two Zn2 ions and two different H2O molecules coordinated
axially to Zn3 and Zn4 ions in the other paddle-wheel (Zn3–O2W 2.022(8) Å and Zn4–O1W 1.957(6)
Å).
Carboxylic groups of H4bdcpp ligand adopt μ1-η0:η1, μ2-η1:η1, μ1-η1:(η1)(elongated
Zn–O)
coordinating modes (Scheme S1a and S1b) to bridge four Zn1 atoms and four paddle-wheels to give
star-shaped SBUs being similar to macrocyclic porphyrin molecule (Fig. 2b). The diagonal
dimensions of star-shaped SBUs are in mesoscale of 25.834 Å. The SBUs interlinking through 1D
Zn1/bdcpp single strand lean against to form 1D ribbon-like chain along the crystallographic c axis
(Fig. 2c and 2d). Further, these ribbons are extended into 2D bilayered structure by Zn2–Zn2
paddle-wheels (Fig. 2e). Topologically, the Zn1 centers and Zn2(COO)4 paddle-wheels serve as
3-connected and 4-connected nodes, respectively. Therefore, MOF 1 is an unusual binodal 3,4-c 2D
bilayered network, which is not reported in RCSR database [14].
（a）

（b）
（c）
（d）

（e）
Fig. 2. (a) Coordination modes of Zn(II) ions in complex 1, symmetry codes: A x, y, z+1; B x, -y+1, z; C -x, -y+1,
-z+2; D x, -y, z; (b) star-shaped stuctural unit similar to macrocyclic porphyrin molecule; (c) 1D polymeric ribbon
by the cross-linking of star-shaped units; (d) 1D Zn-ligand straight chain; (e) 2D bilayer coordination network.
3.2.2. Crystal structure of complex 2
Single-crystal analysis revealed that complex 2 crystallizes in the triclinic Pī space group, that
the 2D anionic layer consists of typical Zn2(COO)4 paddle-wheel units. Similar to 1, the unknown
cationic guest molecules fill into the micropores of the framework 2 to fit the global charge balance.
The asymmetric unit of complex 2 contains two Zn2+ ions, one deprotonized bdcpp4- ligand and one
deprotonized-partially Hbdcpp3- ligand (see Fig. 2a). The Zn1 and Zn2 adopt a distorted tetragonal
pyramidal geometry with {ZnO5} coordination mode. Two adjacent Zn1 centers are linked together
by four carboxylic groups of two deprotonized bdcpp4- to afford the Zn2(COO)4 paddle-wheel
building units, and the carboxylic oxygen atoms of two Hbdcpp3- ligands locate at the axial sites. But,
the paddle-wheels from Zn2 centers are composed of the Hbdcpp3- paddles and the bdcpp4- fixed
axes.
Carboxylic groups of bdcpp4- and Hbdcpp3- display μ1-η0:η1 and μ2-η1:η1coordinating modes
(Scheme S1c and S1d) to link paddle-wheel units to produce irregular square grids with the
dimensions of 9.873(3) × 9.884(3) Å2 (Fig. 2b). These fundamental square grids orient an ordered
arrangement into 2D monolayers (Fig. 2c). The framework topology of 2 could be viewed as a
4-connected uninodal sql (4,4) net with Point Symbol of {44.62} by considering the Zn2(COO)4 unit

as a 4-c node. Interestingly, heterochiral helical chains appearing in couples through paddle-wheel
units and ligand molecules coexist in the framework to produce mesomeric networks (Fig. 2d). The
helices are made up of the repeated moieties “—Zn2(COO)4—ligand—Zn2(COO)4—ligand—” with
the screw pitch of 13.7 Å.
（a）
（b）
（c）

（d）
Fig. 3. (a) Coordination environment of Zn(II) ions in complex 2, symmetry codes: A -x+1, -y+1, -z+2; B -x, -y,
-z+2; (b) quadrilateral unit from Zn2(COO)4 paddle-wheels and organic ligands; (c) 2D grid squares; (d)
heterochiral helical chains appearing in couples through paddle-wheel units and ligand molecules.
3.2.3. Crystal structures of complexes 3 and 4
Utilization of pure organic solvents in synthetic systems yields isostructural MOFs 3 and 4.
Seeing Fig. 4 and 5, organic ligands bridge Zn2(COO)4 paddle-wheels and Zn ions to form identical
1D loop ladder chains except the axial DMF and NMP of paddle-wheels in 3 and 4 separately.
Because the MOFs have the similar frameworks, only the structure of 3 is described here. The X-ray
studies show that complex 3 belongs to the monoclinic C2/c space group and consists of two
crystallographically independent Zn(II) ions, one deprotonized bdcpp4- ligand, one coordinate DMF
molecule and two coordinate water in the asymmetric unit. As shown in Fig. 4a, Zn1 shows a
pyramidal geometry of {ZnO5}, and two Zn1 ions linking four carboxylic groups of two bdcpp4-
ligands afford the Zn2(COO)4 paddle-wheel cluster. In view of the non-negligible Zn2−O6B (2.635
Å) , Zn2 bonds with two carboxylic groups of two bdcpp4- ligands and two water molecules to
produce the 5+1 {ZnO6} modes with distorted octahedral environment.
Four carboxylic groups of deprotonized bdcpp4- link paddle-wheel clusters and Zn ions in
μ2-η1:η1and μ1-η1:(η1)(elongated Zn–O) coordinating modes to form 1D chains running along the b
crystallographic axis (Scheme S1e). As Fig. 4b shows, the binuclear Zn(II) cluster connects to two

ligands in four directions as a 4-connected node, and Zn2 does in two directions as a linear linker.
The framework of 3 could be viewed as a 1D loop ladder structures with the size of 9.38 × 16.44 Å2
(defined by the diagonal distance of the rhombus grids).
（a）
（b）
Fig. 4. (a) Coordination environment of Zn(II) ions in complex 3, symmetry codes: A -x+1, y, -z+1/2; B x, y-1, z;
(b) 1D loop ladder chain from Zn2(COO)4 paddle-wheels and organic linkages.
（a）

（b）
Fig. 5. (a) Crystallographic environment around Zn(II) ions in complex 4, symmetry codes: A -x, y, -z+1/2; B x,
y-1, z; (b) view of 1D chain.
3.3. Effect of different solvent systems on the MOFs structures
According to the structural analyses of MOFs 1-4 above, different crystal structures were
induced from the same precursors by the solvent interference. The solvent types and constitutes (v/v)
in 1-4 are DMF / H2O of 7:3, DMF with little water, DMF and DMF / NMP of 1:1, respectively.
Complex 1 is an unusual 3,4-c binodal 2D bilayering framework, complex 2 represents a 4-c
uninodal 2D (4,4) sql planar network possessing two kinds of chiral helix chains, however,
complexes 3 and 4 are 1D loop ladder chains except different axial coordinate solvent molecules. In
all MOFs, Zn2(COO)4 paddle-wheels acting as SBUs participate in the construction and structural
reinforcement of crystal materials. The formation of paddle-wheel units should be ascribed to two
neighboring 2-carboxylic groups of H4bdcpp ligand, which exemplifies the component selection in
the designed synthesis of MOFs.
Obviously, four congenetic zinc(II) MOFs are generated through delicate solvent-regulated
strategy. Because of the insolubility of large-sized molecules, polar aprotic DMF was used as
excellent mother solvent to promote the solubility and crystallization of the products. The
appropriate amount of water adding into DMF solvent facilitates the ionization of polycarboxylic
acids, thus the coordination ability and bonding degree of organic ligands were improved to form
more complicated crystal structures [15]. This solvent-regulated strategy proposes a proper approach
to the structural fine-tuning of MOFs with a given raw reactant in reticular chemistry.
3.4. Phase analyses and thermal stabilities

PXRD technique has been used to detect the phase purity of the bulk samples of MOFs 1-3 in
the solid state (Fig. S1). The PXRD patterns of as-synthesized powders of 1-3 match well with those
of the single-crystal simulated, which confirms the crystalline phase purities.
Thermogravimetric analyses (TGA) were carried out to testify the thermal stability of
complexes 1-3 (Fig. 6). 1 and 2 keep stable below ca. 60 °C and with the temperature increasing, the
sustained mass loss of MOFs materials began soon. The solvent escaping and framework collapse
last until 530 °C and 550 °C with the final remnant 22.0 % and 17.2 %, respectively. The TG curve
of 3 presents a platform in the range of ambient temperature to 120 °C and the framework starts to
decompose until 530 °C. A final weight residual of 25.8 % corresponds rightfully to the ZnO solid.
Fig. 6. TG curves of MOFs 1–3.
3.5. Photoluminescent properties
The solid-state emission spectra of free ligands and complexes 1-3 were examined at room
temperature (Fig. 7). The free H4bdcpp powders display an emission maximum at 390 nm upon
excitation at 340 nm, which is assigned to ligand-centered π–π* electronic transitions. Under the
irradiation of 290 nm ultraviolet light, bulk samples of complexes 1-3 exhibit a sharp emission at 357
nm, 363 nm and 353nm, respectively. The blue shift of 33 nm, 27 nm, and 37 nm of complexes 1-3,
compared with the emission spectra of free ligand, should be attributed to metal-to-ligand charge
transfer (MLCT) or intraligand (π-π*) charge emission (ILCT) [16]. The enhanced luminescent
emission of the MOFs, far stronger than free H4bdcpp, may be originated from Zn/bdcpp
coordination, strong interaction of Zn2(COO)4 paddle-wheels and compact crystal packing. These
results indicate that such MOF materials could be good candidates for potential photoactive

fluorescent probes [17].
Fig. 7. Fluorescent emission spectra of MOFs 1–3 and free H4bdcpp in the solid state.
4. Conclusions
In conclusion, an intriguing MOF system was constructed from Zn2(COO)4 paddle-wheels
SBUs and V-shaped tetracarboxylate linker. The judiciously solvent-regulated strategy induced four
congenetic zinc(II)-based MOFs with various frameworks including 1D loop ladder chains, 2D sql
plane and 2D bilayered structure. The results exemplified the solvent types and constitutes in
synthetic system play an important role in the microstructural fine-tuning of MOFs. Compared with
free ligand, bulks of synthesized MOFs present excellent luminescent emission with the higher
intensity. A deeper exploration of solvent effect in the syntheses of MOFs crystalline materials with
aromatic polycarboxylates will lead to the discovery of more controllable framework architectures.
Acknowledgements
This work was financially supported by the National Natural Science Foundation of China
(Grant Nos. 21301062, 201601145), the Key Natural Science Research Project of Anhui Provincial
Colleges and Universities (Grant Nos. KJ2019A0691, KJ2016A667), and Anhui Provincial Natural
Science Foundation (Grant Nos. 1308085QB36, 1808085ME109).
Appendix A. Supplementary material

Supplementary pictures and tables for 1-4. See http://dx.doi.org/???. The crystal and refining data of
complexes 1-4 can be obtained free of charge from the Cambridge Crystallographic Data Centre via
www.ccdc. cam.ac.uk/data_request/cif.
References
[1] (a) M. Zhang, W. Zhou, T. Pham, K. A. Forrest,ꢀW. Liu, Y. He, H. Wu, T. Yildirim, B. Chen, B.
Space, Y. Pan, M.J. Zaworotko, J. Bai, Angew. Chem. Int. Ed. 56 (2017) 11426;
(b) Y.-J. Cheng, R. Wang, S. Wang, X.-J. Xi, L.-F. Ma, S.-Q. Zang, Chem. Commun. 54 (2018)
13563;
(c) Q. Yang, C.-C. Yang, C.-H. Lin, H.-L. Jiang, Angew. Chem. Int. Ed. 58 (2019) 3511.
[2] (a) Y.-Z. Chen, R. Zhang, L. Jiao, H.-L. Jiang, Coord. Chem. Rev. 362 (2018) 1;
(b) J.-C. Jin, J. Wu, G.-P. Yang, Y.-L. Wu, Y.-Y. Wang, Chem. Commun. 52 (2016) 8475;
(c) J. Liu, G. Liu, C. Gu, W. Liu, J. Xu, B. Li, W. Wang, J. Mater. Chem. A 4 (2016) 11630;
(d) Y.-P. Wu, G.-W. Xu, W.-W. Dong, J. Zhao, D.-S. Li, J. Zhang, X. Bu, Inorg. Chem. 56 (2017)
1402;
(e) L.-L. Gong, W.-T. Yao, Z.-Q. Liu, A.-M. Zheng, J.-Q. Li, X.-F. Feng, L.-F. Ma, C.-S. Yan,
M.-B. Luo, F. Luo, J. Mater. Chem. A 5 (2017) 7961.
[3] (a) Y.-L. Wu, F.-S. Guo, G.-P. Yang, L. Wang, J.-C. Jin, X. Zhou, W.-Y. Zhang, Y.-Y. Wang,
Inorg. Chem. 55 (2016) 6592;
(b) H.-R. Fu, Y. Zhao, Z. Zhou, X.-G. Yang, L.-F. Ma, Dalton Trans. 47 (2018) 3725;
(c) C. Chen, M. Zhang, W. Zhang, J. Bai, Inorg. Chem. 58 (2019) 2729;
(d) Z. Yin, Y.-L. Zhou, M.-H. Zeng, M. Kurmoo, Dalton Trans. 44 (2015) 5258.
[4] (a) Y.-P. Wu, W. Zhou, J. Zhao, W.-W. Dong, Y.-Q. Lan, D.-S. Li, C. Sun, X. Bu, Angew. Chem.
Int. Ed. 56 (2017) 13001;
(b) I.M.L. Rosa, M.C.S. Costa, B.S. Vitto, L. Amorim, C.C. Correa, C.B. Pinheiro, A.C.
Doriguetto, Cryst. Growth Des. 16 (2016) 1606;
(c) A. Dutta, K. Koh, A.G. Wong-Foy, A.J. Matzger, Angew. Chem. Int. Ed. 54 (2015) 3983;
(d) J. Nierengarten, I. Nierengarten, M. Holler, A. Sournia-Saquet, B. Delavaux-Nicot, E. Leoni,
F. Monti, N. Armaroli, Eur. J. Inorg. Chem. 22 (2019) 2665.
[5] (a) J. Jiang, Z. Lu, M. Zhang, J. Duan, W. Zhang, Y. Pan, J. Bai, J. Am. Chem. Soc. 140 (2018)

17825;
(b) H.-R. Fu, Y. Zhao, Z. Zhou, X.-G. Yang, L.-F. Ma, Dalton Trans. 47 (2018) 3725;
(c) J. Pang, S. Yuan, J. Qin, M. Wu, M. Wu, C. T. Lollar, J. Li, N. Huang, B. Li, P. Zhang, H.-C.
Zhou, J. Am. Chem. Soc. 140 (2018) 12328;
(d) M. Ding, R. W. Flaig, H.-L. Jiang, O.M. Yaghi, Chem. Soc. Rev. 48 (2019) 2783;
(e) M.D. Allendorf, V. Stavila, CrystEngComm 17 (2015) 229.
[6] (a) Z.-Y. Li, W.-J. Wang, D.-Q. Wu, C. Zhang, F.-L. Zhang, B. Zhai, J.-J. Zhang,
CrystEngComm 21 (2019) 4098;
(b) K. Tan, N. Nijem, Y. Gao, S. Zuluaga, J. Li, T. Thonhauser, Y.J. Chabal, CrystEngComm 17
(2015) 247;
(c) A. Gallego, C. Hermosa, O. Castillo, I. Berlanga, C.J. Gómez-García, E. Mateo-Martí, J.I.
Martínez, F. Flores, C. Gómez-Navarro, J. Gómez-Herrero, S. Delgado, F. Zamora, Adv.
Mater. 25 (2013) 2141.
[7] (a) M.Y. Masoomi, M. Bagheri and A. Morsali, CrystEngComm 19 (2017) 5749;
(b) D.-M. Chen, J.-G. Ma, P. Cheng, Dalton Trans. 44 (2015) 8926;
(c) Z. Akimbekov, D. Wu, C.K. Brozek, M. Dincă, A. Navrotsky, Phys. Chem. Chem. Phys. 18
(2016) 1158;
(d) T. Kundu, M. Wahiduzzaman, B.B. Shah, G. Maurin, D. Zhao, Angew. Chem. Int. Ed. 58
(2019) 8073;
(e) X.-P. Wang, W.-M. Chen, H. Qi, X.-Y. Li, C. Rajnák, Z.-Y. Feng, M. Kurmoo, R. Boča, C.-J.
Jia, C.-H. Tung, D. Sun, Chem. Eur. J. 23 (2017) 7990.
[8] (a) Q. Yang, X. Chen, Z. Chen, Y. Hao, Y. Li, Q. Lu, H. Zheng, Chem. Commun. 48 (2012)
10016;
(b) R. Bolligarla, G. Durgaprasad, S.K.Das, Inorg. Chim. Acta 486 (2019) 412.
[9] (a) M.-L. Yue, Y.-F. Jiang, L. Zhang, C.-Y. Yu, K.-Y. Zou, Z.-X. Li, Chem. Eur. J. 23 (2017)
15680;
(b) R.K. Tiwari, J.N. Behera, CrystEngComm 20 (2018) 6602;
(c) C.X. Bezuidenhout, V.J. Smith, C. Esterhuysen, L.J. Barbour, J. Am. Chem. Soc. 139 (2017)
5923;
(d) Y. Wang, H. Cao, B. Zheng, R. Zhou, J. Duan, Cryst. Growth Des. 18 (2018) 7674.

[10] (a) X. Wang, M. Hu, J.-Y. Tian, C.-S. Liu, CrystEngComm 18 (2016) 2864;
(b) Y. Wang, W. Fan, X. Wang, Y. Han, L. Zhang, D. Liu, F. Dai, D. Sun, Inorg. Chem. Front.
5 (2018) 2408;
(c) S. Skoulika, M.G. Siskos, A. Michaelides, CrystEngComm 21 (2019) 1137.
[11] J. Zhao, Y. Wang, W. Dong, Y. Wu, D. Li, B. Liu, Q. Zhang, Chem. Commun. 51 (2015) 9479.
[12] L. Fan, Y. Zhang, J. Liang, X. Wang, H. Lv, J. Wang, L. Zhao, X. Zhang, CrystEngComm 20
(2018) 4752.
[13] (a) G.M. Sheldrick, SHELXS, University of Göttingen, Germany, 1997;
(b) G.M. Sheldrick, SHELXL, Program for the Refinement of Crystal Structures, University of
Göttingen, Germany, 1997.
[14] M. O'Keeffe, M.A. Peskov, S.J. Ramsden, O.M. Yaghi, Accts. Chem. Res. 41 (2008) 1782.
[15] (a) Y. Zhang, Y. Wang, L. Liu, N. Wei, M.-L. Gao, D. Zhao, Z.-B. Han, Inorg. Chem. 57 (2018)
2193;
(b) X. Duan, R. Lv, Z. Ji, B. Li, Y. Cui, Y. Yu, G. Qian, Inorg. Chem. Front. 5 (2018) 1193;
(c) Y. Ye, Z. Ma, L. Chen, H. Lin, Q. Lin, L. Liu, Z. Li, S. Chen, Z. Zhang, S. Xiang, J. Mater.
Chem. A 6 (2018) 20822.
[16] (a) W.-H. Huang, J. Ren, Y.-H. Yang, X.-M. Li, Q. Wang, N. Jiang, J.-Q.i Yu, F. Wang, J.
Zhang, Inorg. Chem. 58 (2019) 1481;
(b) B. Casanovas, S. Speed, O. Maury, M.S. El Fallah, M. Font-Bardía, R. Vicente, Eur. J.
Inorg. Chem. 34 (2018) 3859;
(c) X.-F. Zheng, L. Zhou, Y.-M. Huang, C.-G. Wang, J.-G. Duan, L.-L. Wen, Z.-F. Tian, D.-F.
Li, J. Mater. Chem. A 2 (2014) 12413;
(d) Y. Cui, Y. Yue, G. Qian, B. Chen, Chem. Rev. 112 (2012) 1126.
[17] (a) Z. Hu, B.J. Deibert, J. Li, Chem. Soc. Rev. 43 (2014) 5815;
(b) B. Parmar, Y. Rachuri, K.K. Bisht, E. Suresh, Inorg. Chem. 56 (2017) 10939;
(c) W.O. Lustig, S. Mukherjee, N.D. Rudd, A.V. Desai, J. Li, S.K. Ghosh, Chem. Soc. Rev. 46
(2017) 3242.
Highlights:
• Four new solvent-regulated congenetic zinc(II)-based MOFs were synthesized solvothermally.

• MOFs materials were characterized by single-crystal XRD, elemental analysis, FT-IR, PXRD,
TGA and photoluminescent techniques.
• Various frameworks including 1D loop chains, 2D sql plane and 2D bilayered structure were
created.
• This approach for solvent-regulated strategy to allow the structural fine-tuning provides a good role
model in reticular chemistry.
Graphical Abstract - synopsis
Four congenetic zinc(II) MOFs from delicate solvent-regulated strategy: structural diversities and
fluorescent properties
Gui-Lin Wen,* Bo Liu,* Dao-Fu Liu, Feng-Wu Wang, Li Li, Liang Zhu, Dong-Mei Song, Chao-Xiu Huang,
Yao-Yu Wang
A judiciously solvent-regulated strategy induced four congenetic zinc(II)-based fluorescent MOFs including
1D loop chains, 2D sql plane and 2D bilayer.
Graphical Abstract - pictogram