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Wang et al. Sci China Chem
line), which was further improved to >99% at even lower
temperature (80 °C) by using a purple LED light (emission at
405 nm, 10 W, entry 9). Subsequently, lower reaction tem-
peratures (i.e., 60 °C), other solvents (i.e., N,N-di-
methylformamide (DMF), DMAc and nBuOH) and bases
(i.e., Cs2CO3, K2CO3, Na2CO3) were investigated with
Cu@L6, providing 27%–85% yields of 4-n-butylaniline
(entries 10–11) in 48 h irradiation time. When 5 mol% cat-
alyst was used, 88% yield was obtained (entry 12).
Subsequently, L6 and Cu@L6 were characterized by a
variety of measurements. In the Fourier transform infrared
(FT-IR) spectra (Figure 2(a)), the signals in the range from
1,750–1,650 and 3,450–3,250 cm−1 were attributed to the
vibration of the C=O and N–H bonds, respectively, indicat-
ing the formation of amide during the condensation poly-
merization, and suggesting that the polymer’s backbone was
retained during the coordination with copper. When analyzed
by ultraviolet-visible (UV-Vis) spectroscopy (Figure 2(b)),
the copper complex gave the strongest adsorption at 410 nm
in the visible-light range, which was consistent with the
emission wavelength of LED employed in the coupling re-
action. As shown in Figures 2(c1, c2), the formation of
copper complex also caused a color change from light purple
to brown. The high thermal stability of L6 and Cu@L6 were
confirmed by thermo-gravimetric analysis (TGA), affording
5% mass loss at 372 and 395 °C, respectively (Figure S3,
(BET) measurement was used to study the porosity of L6 and
Cu@L6 by analyzing the N2 adsorption and desorption iso-
therms (Figure 2(d)). In comparison to L6, a smaller surface
area of Cu@L6 was detected (396 vs. 237 m2/g), resulted
from partial occupation of the porous structure by the in-
troduced Cu. The hierarchically porous property was also
proven by the pore size distribution according to the nonlocal
density functional theory (NLDFT) [33]. The results shown
in Figure 2(e) demonstrated the presence of narrowly dis-
tributed pore sizes of about 2 and 5 nm, representing mixed
micropores and mesopores of Cu@L6, which is advanta-
geous for heterogeneous catalysis owing to the excellent
adsorption of substrates and efficient mass transport of
products that could be provided by porous carriers. When
analyzed by scanning electron microscopy (SEM), corre-
sponding images (Figure 2(f, g)) displayed distinctive
morphologies of porosity for L6 and Cu@L6. The high-
resolution transmission electron microscopy (HR-TEM)
images of L6 and Cu@L6 (Figure 2(h, i)) showed their
amorphous structures and the well dispersity of Cu in the
matrix. Otherwise, when L6 and Cu were mixed at their solid
states, Cu nanoparticles are clearly observed by HR-TEM as
confirmed by the lattice fringes with a spacing distance of
0.21 nm (Figure S3) [34]. Additionally, scanning transmis-
sion electron microscopy (STEM) and element mapping
Figure 2 Characterization of L6 and Cu@L6. (a, b) FT-IR and UV-Vis
spectra; (c) optical images; (d) adsorption (filled symbols) and desorption
(empty symbols) isotherms recorded under N2 atmosphere; (e) pore size
distribution obtained by NLDFT; (f, g) SEM images of L6 and Cu@L6,
respectively; (h, i) HR-TEM images of L6 and Cu@L6, respectively; (j1)
STEM image of Cu@L6; (j2–j4) element mapping images of Cu@L6
based on (j1) (color online).
images of Cu@L6 (Figure 2(j1–j4)) further confirm that the
Cu, C and N elements were evenly dispersed on the poly-
meric support, which prompts efficient catalytic process.
With the optimized conditions, we investigated the sub-
strate scope of the photo-promoted Cu-catalyzed C-N cou-
pling between (hetero)aryl chlorides and nitrogen
nucleophiles. As shown in Scheme 1, for nucleophiles of
both aqueous ammonia and substituted amines, the coupling
could be successfully carried out with para-, meta-, and
ortho-substituted aryl compounds and fused aryl substrates
at 80 °C; electron-rich, electron-neutral, and electron-defi-
cient aryl chlorides all represented excellent substrates.
Moreover, the reaction condition tolerated a variety of
functional groups including unprotected hydroxyl (6, 7, 27,
28), amine (8), acetyl (9, 29), sulfamide (10), amide (11, 30),
nitrile (12, 31) and ester (16, 34).
While heteroaryl amines have shown profound research
value for their biological activity [35,36], the copper-cata-
lyzed reactions for this class of substrates remain challenging
due to the proneness of heterocycles to coordinate to copper
species [37,38]. With this method, a variety of heterocyclic
compounds including pyridine (18, 36), thiophene (19, 37),