ic9b01819_si_001.pdf (76.16 kB)
Function–Structure Relationship in Metal–Organic Frameworks for Mild, Green, and Fast Catalytic C–C Bond Formation
journal contribution
posted on 2019-10-18, 15:04 authored by Sayed
Ali Akbar Razavi, Ali MorsaliTunability
in chemical functionality is a promising characteristic
of metal–organic frameworks (MOFs), which plays an important
role in developing and improving the practical applications of MOFs.
Here, we applied this important feature of MOFs to be in line with
sustainable development and green chemistry principles through the
synthesis of MOF-based heterogeneous organocatalysts. According to
our green functionalization strategy, some isostructural MOFs (azine
decorated TMU-4 with the formula [Zn(OBA)(BPDB)0.5]n·2DMF, azine-methyl functionalized TMU-5
with the formula [Zn(OBA)(BPDH)0.5]n·1.5DMF, dihydro-tetrazine decorated TMU-34 with the
formula [Zn(OBA)(H2DPT)0.5]n·DMF, and tetrazine functionalized TMU-34(−2H)
with the formula [Zn(OBA)(DPT)0.5]n·DMF, where H2OBA = 4,4′-oxybis(benzoic
acid), BPDB = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, BPDH = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene,
H2DPT = 3,6-di(pyridin-4-yl)-1,4-dihydro-1,2,4,5-tetrazine,
and DPT = 3,6-di(pyridin-4-yl)-1,2,4,5-tetrazine) have been applied
for mild, green, and fast Knoevenagel condensation. These frameworks
display different Lewis basic catalytic activities owing to their
different functionality and function accessibility. Contrary to extensive
articles published about Knoevenagel condensation, this study involves
the rare examples in Knoevenagel condensation with such mild conditions
(room temperature and atmospheric pressure) and with a green solution
(water as the solvent). Due to the combined synergic effects of the
Lewis basicity of TMU-frameworks, the amphoteric and hydrogen bond-participating
nature of water molecules, maximum conversion times are reached just
after 30 min (for TMU-5) and 60 min (for TMU-34). Stability and recyclability
tests show that TMU-5 and TMU-34 are completely stable in water at
reaction conditions and can retain their crystallinity, porosity,
and functionality even after five cycles without any specific reduction
in their catalytic conversion. Since, in many cases, amine decorated
MOFs are applied in Knoevenagel catalyzed condensation, this study
is beneficial in providing information about the effects of azine
and tetrazine functional groups in reactant activation and the acceleration
of Knoevenagel condensation.