Chemistry Reference
In-Depth Information
Fig. 2.9
A secondary building unit is formed by linking three tetrahedral units with the planar
triangular ring, (
a
) and (
b
). These building units connected together can produce the expanded
ctn (
c
) and bor (
d
) nets, respectively
2.3.3 Structure of Building Blocks
Besides the reasonable reactions, the structure of the building blocks should be
elaborately designed to match the demand for production of crystalline and
ordered COFs. The understanding of the DCC and the concept of topological
structure will provide vital guidelines for the fabrication of COF architectures.
According to this knowledge, the design and synthesis of COF materials could be
more targeted. It is noted that the reactions and the monomers should be consid-
ered simultaneously. It has been documented that the reactions shown in Fig.
2.7
are effective to produce COFs, so these reactions are the best and primary choice.
In addition, based on the reported reactions, the monomers should possess the
following reactive groups, including -B(OH)
2
, diols, -CHO, -NH
2
, and -CN,
which will trigger the dynamic covalent bond formation. Apart from the reactive
groups, the structure of the building blocks must have suitable geometry, which
could determine the final structure of COF. After careful consideration, the
suitable candidates are selected to meet the requirement.
Compared with the relatively fixed functional groups, the geometries of the
monomers are more complicated. Topology offers a powerful tool that could
guide the synthesis of COFs. To obtain COFs with ordered and porous structures,
