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molecular building blocks can effectively tune the framework connectivity, pore
size, and surface area and thereby optimize its hydrogen sorption capacity. Yaghi
and coworkers synthesized a series of mesoporous MOFs with ultrahigh surface
area, which exhibited large total hydrogen uptake at 77 K [
1
]. Zhou et al. prepared
mesoporous PCN-105 presenting hydrogen uptake at 1.0 bar of 1.51 wt% at 77 K
and 1.06 wt% at 87 K, respectively [
2
]. Generally, the functionality of the organic
linkers has little influence on hydrogen sorption and a large MOF cavity does not
make effective contributions to excess hydrogen uptake capacities. Improving the
interactions between H
2
and the framework presents a major challenge and bot-
tleneck for MOFs to store hydrogen in a practical manner. An alternative high-
density fuel source to hydrogen and gasoline is methane due to its cleaner and
more abundant nature. The methane adsorption capacity in micro-/mesoporous
UMCM-1 at 298 K could reach 8.0 mmol g
−
1
at 24.2 bar [
3
]. Noticeably, unlike
hydrogen, the interactions between methane and the aromatic hybrid framework
are strong enough. The safe, cheap, and convenient means for methane storage are
still in its deficiency. Rigorous research toward robust and available mesoporous or
even hierarchical porous hybrid materials for large-scale applications is urgently
needed.
The capture of greenhouse gases such as CO
2
under practical conditions is quite
significant because of the implications for global warming, and the removal of
CO
2
from industrial flue gas has become an important issue. One feasible option
to curtail the rise of the threats is to capture CO
2
from the combustion of fossil
fuels. Among a number of CO
2
capture solids including porous carbons [
4
,
5
],
amine-modified mesoporous silicas [
6
], and carbon-CaO nanocomposites [
7
],
exhibiting certain advantages such as high surface area, large pore volume, uni-
form pore width, low cost, and relatively high stability is promising for CO
2
cap-
ture over a wide range of operating conditions. In recent years, much attention has
been focused on mesoporous non-siliceous hybrids for CO
2
capture due to ultra-
high surface area, adjustable surface chemistry, and relatively low cost [
8
-
10
]. The
CO
2
uptake of the cubic mesoporous titanium phosphonates was approximately
1.0 mmol g
−
1
at 35 °C [
11
], which was much higher than some pure silica adsor-
bents and comparable with some amino-modified mesoporous silica with similar
surface areas [
12
]. Theoretically, the incorporation of accessible nitrogen donor
groups into the network of porous materials can dramatically influence the gas
uptake ability, especially for base carbon oxide [
4
]. Thus, combined with the supe-
riority of large surface area and high pore volume, the CO
2
uptake capability could
be enhanced obviously (about 36.7 wt% at 1 atm and 273 K) when nitrogen-rich
organic linkages were intentionally used [
13
]. Recent theoretical and experimen-
tal studies have revealed the correlation between the amount of CO
2
adsorbed and
the surface area or pore volume, as well as the increase of adsorption enthalpy for
the host materials with open metal sites and active organic functionalities [
4
,
14
].
In particular, the incorporation of mesoporosity and even hierarchical porosity can
optimize the adsorption capacity and kinetics. The CO
2
adsorption equilibrium for
meso-/macroporous titanium phosphonates (B-Ti-1/2) could be reached within
50 min [
15
] (Fig.
5.2
). The CO
2
uptake was 0.89 mmol g
−
1
at 40 °C, which was
comparable with commercially activated carbon [
16
].
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