D. Shi, et al.
Inorganic Chemistry Communications 105 (2019) 9–12
Fig. 1. (a) The coordinate environment of Cu1
ions in Cu–TPA [Symmetry operation: (A): 1 – x,
y, 1.5 – z]. (b) View of the 3D anionic frame-
−
work of [Cu
2
(TPA)] along the c direction. (c)
View of the 3D framework of Cu–TPA (TBA
drawn as green). (d) The 2-nodal (3,5)-con-
nected topological network for Cu–TPA. (For
interpretation of the references to color in this
figure legend, the reader is referred to the web
version of this article.)
that can be used for further functionalization, which is a powerful
strategy for CeC bond formation [4,5]. Bearing in mind the use of toxic,
expensive, and irrecoverable noble-metal polypyridyl complexes as
photocatalysts in the reported procedures [6–8], it is highly desirable to
develop the CeC coupling reactions in the presence of heterogeneous
photocatalysts constructed from earth-abundant elements and less
harmful organic ligands.
earth-abundant and relatively low-cost materials have been character-
1
0
ized by the d electronic configuration and show the relatively intense
luminescent behavior [20]. Herein, we report a tetrazole-containing
triphenylamine-based MOF, {TBA[Cu
2
(TPA)]}·CH
3
CN (Cu–TPA;
remarkable
TBA = tetrabutylammonium cation), which exhibits
a
photocatalytic activity for the CeC coupling reaction of N-aryl-tetra-
hydroisoquinoline and nitromethane with excellent yield and out-
standing durability.
Metal–organic frameworks (MOFs) are hybrid solids with infinite
network structures built from inorganic connecting nodes and organic
bridging ligands [9]. The tenability and flexibility of MOFs granted by
the diversity of their building blocks allow the incorporation of pho-
toactive organic ligands and the necessary adducts into one single fra-
mework, which represents a new approach to heterogenizing photo-
catalytic transformations [10,11]. The regular distribution of catalytic
sites within the confined micro-environment benefits the fixation and
stabilization of the active intermediates formed under irradiation to
overcome restrictions of homogeneous processes [12]. To achieve
precise control of the shifting energy levels of the ground and excited
states and the enhancement of the visible-light harvesting ability of
MOFs, continuous structural modulation of a dye-based ligand scaffold
is highly desirable, however, it is still in its infancy [13].
The orange block crystals of Cu–TPA were synthesized by a sol-
vothermal reaction of CuCl
2
·2H
2
O, H
3
TPA and (TBA)
4
[W10O
32] at
pH 2.5 with a yield of 46% [21]. Elemental analyses and powder X-ray
diffraction (PXRD) reveal the pure phase of bulk sample. Single-crystal
structural analysis indicates that Cu–TPA crystallizes in a monoclinic
space group C2/c [22]. The crystallographically independent Cu(I)
cation adopts a four-coordinate tetrahedral geometry with four nitrogen
atoms from four TPA ligands. Two symmetry-equivalent Cu(I) ions are
linked by three TPA ligands to form a binuclear {Cu } cluster (Fig. 1a).
2
Moreover, these symmetry-equivalent Cu(I) ions are connected by three
nitrogen atoms (N2, N3 and N4) from TPA ligands to produce a 2D
sheet (Fig. S1); adjacent sheets are further coupled together by N6
atoms of TPA ligands to generate the 3D anionic framework of
−
Recently, we have launched the study on the reaction of tetrazole-
containing triphenylamine-based ligand tris(4-(2H-tetrazol-5-yl)
[Cu
2
(TPA)] with embedded TBA cations and CH
3
CN molecules
(Fig. 1b and c). The exchanged experiment of TBA and the assessment
of guest-accessible volume in MOFs can be reliably done by using
confocal fluorescence microscopy with a tool-box of basic orange 14
phenyl)amine (H TPA) with copper metal cations to synthesize the
3
tetrazole-containing triphenylamine-based MOFs for the photocatalytic
CeC coupling reaction based on the following aspects: (1) MOFs con-
taining the tetrazole ring as a multiple-dentate N-donor ligand have
significantly higher structural and thermal stabilities than pyridyl
analogues [14–16]. The increased stability of tetrazolate-containing
frameworks partly stems from the present of multiple-metal-co-
ordinated sites, where the anionic group formed by the deprotonation
of tetrazole ring results in an optimal N-donor ligand that generates
strong coordination bonds with metal cations [17]. (2) A well-known
photo-responsive triphenylamine-based ligand has been successfully
incorporated into MOFs for photocatalytic CeC coupling reactions
+
+
dye (Fig. S8) [23]. In addition, inorganic Na - and Li -exchanged
studies indicate that TBA organic cations in the cavities can be fully
exchanged at room temperature after 48 h, as proven by elemental
analyses and atomic absorption experiments [24]. From the topological
viewpoint, each {Cu } cluster can be regarded as a 5-connected node
2
and each TPA ligand as a 3-connected node. Thus, the framework of
Cu–TPA can be simplified as a 2-nodal (3,5)-connected network
(Fig. 1d).
The IR spectrum of Cu–TPA has been recorded between 4000 and
−1
400 cm
with KBr pellets (Fig. S4). In the high-wavenumber region,
−1 −1
[
18], and its three aryl moieties with their C
3
-symmetry provide po-
three vibration bands observed at 3600–3275 cm , 3096–2990 cm
−1
tential sites for iterative decoration to achieve continuous modulation
of the photoelectronic properties [19]. (3) Copper(I) complexes as
and 2986–2670 cm
are attributed to the ν(NeH) and ν(CeH)
stretching vibration of tetrazole groups, benzene rings and TBA cations,
10
Shi, Dongying
