The separation of
a mixture of C2H2 and CO2 is a great
challenge due to their similar molecular sizes and shapes. Al-based
metal–organic frameworks (Al-MOFs) have great promise for gas
separation applications due to their light weight, high stability,
and low cost. However, the cultivation of suitable Al-MOF single crystals
is extremely difficult and has limited their explorations up to now.
Since In, Ga, and Al are all 3p-block metal elements, a systematic
application of the periodic law to investigate 3p-MOFs will undoubtedly
help in the understanding and development of worthy Al-MOF materials.
Herein, we report the design of a robust 3p metal–organic framework
platform (SNNU-150) and the systematic regulation of C2H2/CO2 separation by open 3p-block metal sites.
X-ray single-crystal diffraction analysis reveals that SNNU-150 is
a 3,6-connected 3D framework consisting of [M3O(COO)6] trinuclear secondary building units (SBUs) and tritopic
nitrilotribenzoate (NTB) linkers. Small {[M3O(COO)6]4(NTB)6} tetrahedral cages and extra-large
{[M3O(COO)6]10(NTB)14}
polyhedral cages connect with each other to generate a hierarchically
porous architecture. These 3p-MOFs present very high water, thermal,
and chemical stability, especially for SNNU-150-Al, which can maintain
its framework at 85 °C in water for 24 h and in a room-temperature
environment for more than 30 days. IAST calculations, breakthrough
experiments, and GCMC simulations all show that SNNU-150 MOFs have
top-level C2H2/CO2 separation performance
and follow the order Al-MOF > Ga-MOF > In-MOF.
The
construction of superstable metal–organic frameworks
(MOFs) for selective gas uptake is urgently demanded but remains a
great challenge. Herein, a unique bifunctional deformed [Ga3O(COO)6] inorganic secondary building unit (SBU) generated
from the desymmetrical evolution of typical triangular prismatic trinuclear
cluster was first introduced, which was extended by an isosceles triangular
organic linker to produce a robust Ga-MOF (SNNU-63).
Remarkably, SNNU-63 can stabilize in water at 25 °C
for 96 h and at 80 °C for more than 24 h, which surpasses nearly
all other Ga-MOFs. The combined effects of open metal sites and hydrophobic
pore environment provided by deformed [Ga3O] SBUs render SNNU-63 with high C2H2 storage capacity
and efficient C2H2 and natural gas purification
performance. The ideal adsorbed solution theory calculation, column
breakthrough tests, and grand canonical Monte Carlo simulations demonstrate
that SNNU-63 is a potential material for addressing the
challenge of C2H2/CO2 and C2H2/CH4 mixture separation under ambient conditions.
High storage capacity, high separation
selectivity, and high structure
stability are essential for an idea gas adsorbent. However, it is
not easy to achieve all three at the same time, even for the promising
metal–organic framework (MOF) adsorbents. We demonstrate herein
that robust [Sc3O]-organic frameworks could be regulated
by a micropore combination strategy for high-performance acetylene
adsorption. Under the same solvent system with formic acid as a modulator,
similar tritopic ligands extend [Sc3O(COO)6]
trigonal-prismatic clusters to generate SNNU-5-Sc and SNNU-150-Sc
adsorbents. Notably, the two Sc-MOFs can keep their architectures
over 24 h in water at different pH values (2–12) or at 90 °C.
Modulated by the linker symmetry, the final stacking metal–organic
polyhedral cages produce open window sizes of about 10 Å for
SNNU-5-Sc and 5 Å + 7 Å for SNNU-150-Sc. Due to such micropore
combinations, SNNU-5-Sc exhibits a top-level C2H2 uptake of 211.2 cm3 g–1 (1 atm and
273 K) and SNNU-150-Sc shows high C2H2/CH4, C2H2/C2H4, and
C2H2/CO2 selectivities of 80.65,
4.03, and 8.19, respectively, under ambient conditions. Dynamic breakthrough
curves obtained on a fixed-bed column and grand canonical Monte Carlo
(GCMC) simulations further support their prominent acetylene storage
and purification performance. High framework stability, storage capacity,
and separation selectivity make SNNU-5-Sc and SNNU-150-Sc ideal acetylene
adsorbents in practical applications.
The exploration of efficient CO2 capture and conversion techniques is of great importance for the global sustainable development. Herein, a novel bi-microporous Sc-MOF, named [Sc3(NTB)2(CH3COO)3] (SNNU-616-Sc, NTB = nitrilotribenzoic acid)...
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