Chemistry Reference
In-Depth Information
simulation of COFs is performed by computational method according to the topol-
ogy of original monomers and the reactions occur. In addition, infrared spectros-
copy, solid-state NMR spectroscopy, elemental analysis, and X-ray photoelectron
spectroscopy (XPS) are all useful to evaluate the linkages, terminal groups, and
compositions of the COFs.
To summarize the development of different COFs, they have some common
features. (1) the structures of COFs are from simple to complex due to their cor-
responding monomers; (2) pore sizes could be controlled; (3) the surface of COFs
is adjusted by suitable function [
14
]. The design and synthesis of COFs have two
key issues that must be considered to achieve thermodynamic control in reversible
reactions: the first is the structure of the building blocks and the second is the syn-
thetic method, including the reaction media and reaction conditions.
2.4 Amorphous POFs
Besides crystalline POFs (also referred as COFs), another major class of POFs is
amorphous networks [
15
,
16
]. Compared with crystalline POFs, the amorphous
POFs are more diverse: (1) the reactions for the synthesis of amorphous POFs are
more abundant than that of synthesis of crystalline POFs; (2) the active groups of
monomers for the synthesis of amorphous POFs are relatively varied; (3) the struc-
ture of building blocks for the synthesis of crystalline POFs is restricted.
Amorphous POFs play vital roles in porous materials and are being actively
pursued as a useful platform for advanced functional material design. Many chem-
ists and materials scientists focus on this field and contribute to the design and
synthesis of POFs. The representative POFs, including polymers of intrinsicmicr-
oporosity (PIMs) [
2
-
4
], HCPs [
17
,
18
], conjugated microporous polymers (CMPs)
[
19
,
20
], and porous aromatic frameworks (PAFs) [
21
-
26
], etc., constitute typical
classes of covalently linked amorphous organic porous materials.
2.4.1 Polymeric Reactions
To create porosity in POFs, the key points of the current method are the choice
of suitable building units and reaction medium. Chemical reactions are exploited
and attempted to prepare POFs. As summarized in Fig.
2.18
, several pioneering
and effective strategies have been employed to construct POFs. To date, more
than 20 effective reactions have been well established; representative examples t
include dibenzodioxane-forming reaction [
2
-
4
], Sonogashira-Hagihara cross-cou-
pling reaction [
27
-
30
], Suzuki cross-coupling reaction [
31
-
33
], Yamamoto type
Ullmann cross-coupling reaction [
34
-
37
] and trimerization reaction of aromatic
nitrile compounds [
38
-
41
], oxidative coupling reaction [
42
], Schiff base reaction
[
43
], Friedel-Crafts reaction [
44
], etc. [
45
-
50
].
