.
Angewandte
Communications
Large-Molecule Adsorption
Clicked Isoreticular Metal–Organic Frameworks and Their High
Performance in the Selective Capture and Separation of Large Organic
Molecules
Pei-Zhou Li, Xiao-Jun Wang, Si Yu Tan, Chung Yen Ang, Hongzhong Chen, Jia Liu,
Ruqiang Zou,* and Yanli Zhao*
Abstract: Three highly porous metal–organic frameworks
(MOFs) with a uniform rht-type topological network but
hierarchical pores were successfully constructed by the assem-
bly of triazole-containing dendritic hexacarboxylate ligands
with ZnII ions. These transparent MOF crystals present
gradually increasing pore sizes upon extension of the length
of the organic backbone, as clearly identified by structural
analysis and gas-adsorption experiments. The inherent acces-
sibility of the pores to large molecules endows these materials
with unique properties for the uptake of large guest molecules.
The visible selective adsorption of dye molecules makes these
MOFs highly promising porous materials for pore-size-
dependent large-molecule capture and separation.
with chemical tunability and together with their diverse
coordination geometries enables them to be tailored into
various frameworks with different pore sizes for target
applications.[1,2] Abundant MOF structures have been fabri-
cated by the judicious combination of organic ligands and
metal ions or metal–cluster secondary building units gener-
ated in situ, and great effort has been dedicated to the
exploration of their application for gas or small-molecule
capture and storage.[2] To extend their applicability to large-
molecule-based applications, such as organic-pollutant
removal, bioimaging, drug delivery, heterogeneous catalysis,
and even selective molecular capture and separation, the
development of efficient MOFs with pores accessible to large
molecules is highly desired.[3,4]
O
wing to their intriguing structures, high porosity, and wide
Versatile click chemistry, that is, copper(I)-catalyzed
azide–alkyne cycloaddition, has been utilized extensively in
the fabrication of various functional materials.[5–7] Since the
reactions can be carried out under mild conditions in high
yield, click chemistry provides a straightforward and effective
approach to the design and synthesis of organic ligands
suitable for the assembly of MOFs.[7] Meanwhile, reticular
chemistry, as exemplified in a series of reported MOFs, has
been well documented as a reliable strategy for the con-
struction of frameworks with predetermined porosity.[8,9]
Desired structural analogues with tailored pore sizes can
been fabricated from such frameworks by employing suitable
ligands to replace initial ligands in a known ordered network.
By taking advantage of convenient click reactions and the
conceptual approach of reticular chemistry, the “click”
extension of isoreticular frameworks should be a feasible
strategy for developing MOFs with pores that are accessible
to large molecules. Herein, we describe the successful
application of this strategy for the fabrication of three
isoreticular MOFs, 1–3,[10] and demonstrate their remarkable
capability for the selective capture and separation of large
molecules.
potential application, metal–organic frameworks (MOFs)
have attracted tremendous attention over the past
decade.[1,2] One inherent structural feature of MOFs that
distinguishes them from other inorganic porous materials,
such as zeolites, porous silica, and activated porous carbon
materials, is that they are hybrid materials with inorganic
units and organic moieties. This characteristic endows them
[*] Dr. P.-Z. Li,[+] Dr. X.-J. Wang,[+] S. Y. Tan,[+] C. Y. Ang, H. Chen,
Prof. Dr. Y. Zhao
Division of Chemistry and Biological Chemistry, School of Physical
and Mathematical Sciences, Nanyang Technological University
21 Nanyang Link, 637371 (Singapore)
E-mail: zhaoyanli@ntu.edu.sg
Dr. J. Liu, Prof. Dr. R. Zou
Beijing Key Laboratory for Theory and Technology of Advanced
Battery Materials
Department of Materials Science and Engineering
College of Engineering, Peking University
Beijing 100871 (China)
E-mail: rzou@pku.edu.cn
Dr. P.-Z. Li,[+] Dr. X.-J. Wang,[+] Dr. J. Liu, Prof. Dr. R. Zou,
Prof. Dr. Y. Zhao
Singapore Peking University Research Centre (SPURc) for a
Sustainable Low-Carbon Future
The rht-type MOF framework usually shows a high
surface area, large open pores, and the absence of framework
interpenetration.[7b,11,12 These salient features make the rht-
type network an ideal prototypical framework for the
development of novel large-pore MOFs by the strategy of
click extension. Thus, a dendritic hexacarboxylate ligand
(H6L), 5,5’,5’’-(4,4’,4’’-(benzene-1,3,5-triyl)tris(1H-1,2,3-tria-
zole-4,1-diyl))triisophthalic acid (H6L1, Figure 1a), was first
designed and successfully synthesized through click chemis-
try. Subsequently, colorless crystals of MOF 1 were obtained
by treatment of the ligand with ZnII ions. Motivated by this
1 Create Way, 138602 (Singapore)
Prof. Dr. Y. Zhao
School of Materials Science and Engineering
Nanyang Technological University
50 Nanyang Avenue, 639798 (Singapore)
[+] These authors contributed equally.
Supporting information and ORCID(s) from the author(s) for this
12748
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 12748 –12752