Fluorine-Functionalized
NbO-Type {Cu2}‑Organic
Framework: Enhanced Catalytic Performance on the Cycloaddition Reaction
of CO2 with Epoxides and Deacetalization-Knoevenagel Condensation
posted on 2022-07-15, 20:06authored byHongtai Chen, Tao Zhang, Shurong Liu, Hongxiao Lv, Liming Fan, Xiutang Zhang
The high catalytic activity of metal–organic frameworks
(MOFs) can be realized by increasing their effective active sites,
which prompts us to perform the functionalization on selected linkers
by introducing a strong Lewis basic group of fluorine. Herein, the
exquisite combination of paddle-wheel [Cu2(CO2)4(H2O)] clusters and meticulously designed
fluorine-funtionalized tetratopic 2′,3′-difluoro-[p-terphenyl]-3,3″,5,5″-tetracarboxylic acid
(F-H4ptta) engenders one peculiar nanocaged {Cu2}-organic framework of {[Cu2(F-ptta)(H2O)2]·5DMF·2H2O}n (NUC-54), which features two types of nanocaged voids
(9.8 Å × 17.2 Å and 10.1 Å × 12.4 Å)
shaped by 12 paddle-wheel [Cu2(COO)4H2O)2] secondary building units, leaving a calculated solvent-accessible
void volume of 60.6%. Because of the introduction of plentifully Lewis
base sites of fluorine groups, activated NUC-54a exhibits
excellent catalytic performance on the cycloaddition reaction of CO2 with various epoxides under mild conditions. Moreover, to
expand the catalytic scope, the deacetalization-Knoevenagel condensation
reactions of benzaldehyde dimethyl acetal and malononitrile were performed
using the heterogenous catalyst of NUC-54a. Also, NUC-54a features high recyclability and catalytic stability
with excellent catalytic performance in subsequent catalytic tests.
Therefore, this work not only puts forward a new solution for developing
high-efficiency heterogeneous catalysts, but also enriches the functionalization
strategies for nanoporous MOFs.