3.2. Reaction between TMC and UiO-66(Zr)-NH2
When
UiO-66(Zr)-NH2 was
mixed with TMC in n -hexane solution, covalent bonds formed
between the amino groups of UiO-66(Zr)-NH2 and acyl
chloride groups of TMC.32-34 These bonds led to the
formation of a uniform and sturdy surface layer that contained MOF
nanoparticles affixed in the polyamide matrix. The formed covalent bonds
were identified in the XPS profiles of
TMC-UiO-66(Zr)-NH2 (Figure 2). The peaks at 284.8,
286.5, and 288.7 eV in the C 1s XPS profile of
UiO-66(Zr)-NH2 corresponded to the C–C, C–N, and
O=C–O bonds, respectively (Figure 2a).32, 33 The
intensity of the characteristic peak of the C–N bond in the XPS spectra
of TMC-UiO-66(Zr)-NH2 was significantly higher than that
in the XPS spectra of UiO-66(Zr)-NH2 (Figure 2b). This
indicated the formation of C–N bonds during the reaction of
UiO-66(Zr)-NH2 with TMC. The N 1s XPS profile of
UiO-66(Zr)-NH2 presented a single peak at 399.5 eV,
which was ascribed to the –NH2 groups (Figure 2c). By
contrast, an additional peak at 401.5 eV was observed in the N 1s
spectra of TMC-UiO-66(Zr)-NH2, and that further
confirmed the formation of O=C–N bonds during the reaction of
UiO-66(Zr)-NH2 with TMC (Figure 2d). The presence of the
new peak at 1730 cm−1 in the FTIR spectrum of
TMC-UiO-66(Zr)-NH2 (Supporting Information, Figure S6a)
also indicated the formation of covalent bonds between
UiO-66(Zr)-NH2 and TMC. Furthermore, the positions of
the peaks in the XRD spectra of TMC-UiO-66(Zr)-NH2 and
UiO-66(Zr)-NH2 did not change significantly, which
indicated the negligible effect of the reaction on the crystal structure
of UiO-66(Zr)-NH2 (Supporting Information, Figure S6b).
The 1H NMR spectrum further confirmed that a reaction
occurred between TMC and UiO-66(Zr)-NH2 (Supporting
Information, Scheme S1 and Figure S7). The covalent bonds that formed
during the reaction tightened the interaction between
UiO-66(Zr)-NH2 and interfacial polymer layer.