**2. Experimental**

## *2.1. Materials and Instrumentations*

All chemicals were purchased from commercial sources and used as received, without further purification.

Gas chromatography (GC) was performed on a Shimadzu GCMS-QP2020 (Kyoto, Japan). The copper content of the catalyst was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES), using a Thermo Fisher Scientific X Series 2 instrument (Waltham, MA, USA). Fourier transform infrared spectra (FT-IR) were collected on a PerkinElmer FT-IR Spectrometer Spectrum Two (Waltham, MA, America) within the spectral range of 4000–400 cm<sup>−</sup>1. X-ray photoelectron spectroscopy (XPS) data were obtained on a Thermo Fisher Scientific K-Alpha instrument (Waltham, MA, America). X-ray powder diffraction (XRD) data were collected on a Rigaku MiniFlex600 diffractometer (Tokyo, Japan), using Cu K α radiation in a range of Bragg's angles (5◦–80◦). Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were conducted with a Zeiss Sigma 300 instrument (Oberkochen, Germany). Thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG) were performed on a Mettler TGA/DSC3+ (Zurich, Switzerland), under a nitrogen atmosphere from 30 to 800 ◦C in a 50 mL·min−<sup>1</sup> N<sup>2</sup> flow and at a ramp rate of 10 ◦C·min−1. 1H NMR (300 MHz) and 13 C NMR (75 MHz) spectra were obtained with a Bruker 300 Avance instrument (Karlsruhe, Germany), with CDCl3 as the solvent and TMS as the internal standard. HRMS was determined by using Agilent 6545 Q-TOF MS (Santa Clara, CA, USA).

#### *2.2. Preparation of CuII/I@CMC-PANI Film*

CMC-Na (0.242 g, 1 mmol) was added to 30 mL aqueous methanol solution (MeOH/H2O, *v*/*v* = 1/2) at room temperature, with continuous stirring until it completely dissolved. Then, aniline monomer (0.0911 g, 1 mmol) was dropped in above the solution to form a homogeneous mixture. This mixture was poured into a Petri dish, and CuSO4 solution (5 wt.%) was finely and evenly misted onto the surface of the mixture using a handheld sprayer. Immediately, a light green interface (extremely thin film) was formed and isolated the CMC-Na/aniline mixture from the CuSO4 solution. The resultant system was stood for 48 h to form a dark green film. The as-formed film was washed thoroughly with methanol and water to remove unreacted aniline and CMC-Na, and dried to afford the CuII/I@CMC-PANI film. The schematic illustration of the preparation process of the CuII/I@CMC-PANI film is shown in Scheme 1.

#### **Scheme 1.** Schematic illustration of the preparation of CuII/I@CMC-PANI film.

#### *2.3. General Procedure for A<sup>3</sup> Coupling Reactions Catalysed by CuII/I@CMC-PANI Dip Catalyst*

Aldehyde (1.0 mmol), amine (1.2 mmol), terminal alkyne (1.5 mmol) and a catalytic amount of CuII/I@CMC-PANI film (15 mg, 2.7 mol% of Cu) were added to 2 mL toluene in a sealed vessel, and the mixture was rigorously stirred at 110 ◦C for the specific time and monitored by TLC. As the reaction was completed, the dip catalyst was picked up with tweezers and washed several times with ethyl acetate and dried at 80 ◦C for the next run. The remaining mixture was extracted with ethyl acetate (3 × 4 mL). Then, the combined organic phase was washed with brine and dried over anhydrous Na2SO4. After removal of the organic solvent by a vacuum rotary evaporator, the crude product was purified by column chromatography on silica gel to afford the corresponding propargylamine. All the products, except product (i), are known, and their 1H NMR and 13C NMR data were found to be identical to those reported in previous literature. The new compound (i) was fully characterized by FT-IR, 1H NMR, 13C NMR, and HRMS. All these data and spectra have been concluded in Supplementary Materials.

#### **3. Results and Discussion**

#### *3.1. Synthesis and Characterization of Catalyst*

The synthetic route of the CuII/I@CMC-PANI film is outlined in Scheme 1. Before the addition of CuSO4 solution, the CMC-Na and aniline monomers were self-assembled together by H-bond interactions [35]. Then, the CuSO4 solution was finely and evenly misted onto the surface of the CMC-Na/aniline mixture, and a light green interface (an extremely thin film) was generated immediately, which separated the CMC-Na/aniline mixture and CuSO4 solution to provide an interfacial layer for aniline to polymerize (Scheme 2). In this process, the CuSO4 solution not only acted as the initiator, triggering the polymerization reaction, but also as the coupling reagent, combining the CMC molecular chain and PANI chain together. In the meantime, Cu(II)/Cu(I) species were deposited into the as-formed CMC-PANI film and stabilized by complexation with carboxylic groups (–COO−), hydroxyl groups (–OH), and nitrogen atoms (–NH– and –N=) to form the target dip catalyst. The Cu content in fresh CuII/I@CMC-PANI film was determined by ICP-AES to be 1.805 mmol/g.

**Scheme 2.** Detailed illustration of spray-assisted interfacial polymerization process.

To verify the composition and structures of the CuII/I@CMC-PANI film, analytical techniques, including FT-IR, XPS, XRD, SEM, EDS, TGA, and DGT, were performed.

The FT-IR spectra of CMC-Na (curve a), PANI (curve b), and the obverse side (curve c) and back side (curve d) of the CuII/I@CMC-PANI film are presented in Figure 1. As shown in the spectrum of CMC-Na (Figure 1, curve a), the characteristic peaks appeared at 1606 cm<sup>−</sup><sup>1</sup> and 1424 cm<sup>−</sup>1, related to the asymmetric and symmetric stretching vibration of carboxylic (–COO−) groups, respectively [36,37]. In the spectra of PANI (Figure 1, curve b), the peaks at 1558 cm<sup>−</sup>1, coupled with 1141 cm<sup>−</sup>1, and 1482 cm<sup>−</sup>1, along with 805 cm<sup>−</sup>1, are assigned to the stretching vibration of quinoid and benzenoid rings, correspondingly [32,38]. Due to the interfacial polymerization, the CuII/I@CMC-PANI film owns obverse and back sides, and they are composed of different components. The characteristic peaks of CMC (carboxylic groups: 1579 cm<sup>−</sup><sup>1</sup> and 1413 cm<sup>−</sup>1) and PANI (quinoid: 1107 cm<sup>−</sup><sup>1</sup> and benzenoid: 1501 cm<sup>−</sup>1) were both observed in the spectra of the catalyst obverse side (Figure 1, curve c), which confirmed that aniline monomers succeeded to the polymerization of PANI onto the CMC molecular chain. However, on the back side, only peaks of carboxylate groups (1582 cm<sup>−</sup><sup>1</sup> and 1414 cm<sup>−</sup>1) appeared (Figure 1, curve d), which means that PANI mostly exists on the obverse side of the catalyst.

**Figure 1.** The FT-IR spectra of CMC-Na (a), PANI (b), the obverse side of CuII/I@CMC-PANI film (c), and the back side of CuII/I@CMC-PANI film (d).

XPS was carried out to further demonstrate the existence of all elements and the oxidation state of copper. Presented in the survey scan spectrum (Figure 2a), C, N, O, and Cu elements are found to be 39.33%, 4.57%, 48.20%, and 7.90%, respectively, in fresh CuII/I@CMC-PANI film. The peaks at 932.78 eV (Cu2p3/2) and 952.48 eV (Cu2p1/2) in Figure 2e, and the peak at 571.12 eV (CuLM2) in Figure 2f, were assigned to the presence of Cu(I) [39]. Meanwhile, the shoulder peaks (934.83 eV and 954.63 eV) and satellites peaks (940.18 eV, 944.07 eV, and 962.56 eV) illustrate that Cu (II) also existed in the catalyst [40]. Notably, nearly all the Cu (II) in the recovered catalyst was turned into Cu(I), evidenced by the disappearance of shoulder peaks and satellites, as well as the presence of peaks at 932.37 eV (Cu2p3/2) and 952.57 eV (Cu2p1/2) in Figure 2g, and the peak at 571.74 eV (CuLM2) [40] in Figure 2h, which means that Cu(I) species may be the true catalyst for A<sup>3</sup> reactions.

**Figure 2.** *Cont*.

**Figure 2.** The XPS survey scan (**a**) of CuII/I@CMC-PANI film and its high-resolution spectra of C1s (**b**), N1s (**c**), O1s (**d**), Cu2p (**e**) and CuLM2 (**f**); XPS high-resolution spectra of Cu2p (**g**) and CuLM2 (**h**) of catalyst recovered from A<sup>3</sup> reaction.

To further confirm the composition of the CuII/I@CMC-PANI film, XRD was performed. The amorphous peak at 2*θ* = 20.6◦ in curve (a) and the broad peak at 2*θ* = 25.2◦ in curve (b) (Figure 3) were attributed to the pristine CMC-Na [41] and PANI powders [42], respectively, showing an extremely low degree of crystallinity. The peak at 2*θ* = 20.6◦ can also be observed in curve (c) of the catalyst, but the peak of PANI was shifted to 2*θ* = 21.8◦, due to the interaction between PANI and CMC-Na [43]. The appearance of CMC and PANI peaks in curve (c) (Figure 3) proves that CMC and PANI were merged successfully into the film. Moreover, as can be found in curve (c) of the catalyst, the films consist of mixed phases of 6CuO·Cu2O (JCPDS 03-0879), CuO (JCPDS 44-0706), Cu2O (JCPDS 35-1091), and Cu4O3 (JCPDS 49-1830). Generally, the 6CuO·Cu2O phase is observed to be an intermediate phase between Cu2O and CuO [44], and Cu4O3 can be written as Cu(I)2Cu(II)2O3 [45]. These observations conclude that Cu (II) and Cu(I) species exist in the catalyst. The size of the particles can be calculated using the Scherrer equation, as follows: D=Kλ/(βcos*θ*) = 0.89×0.15405 0.534 180 ×3.14×cos 28.52 = 15.19 (nm). These data are approximate, with the value of 10.04 nm obtained from the SEM images (Figure 4e,f), due to the Scherrer equation being applicable to nanocrystals with perfect crystallinity, and there may be a certain number of errors to the particles without high crystallinity.

**Figure 3.** The XRD patterns of the CMC-Na (a), PANI (b), and CuII/I@CMC-PANI film (c).

**Figure 4.** SEM images (**<sup>a</sup>**,**e**,**f**) and EDS data (**b**) of the obverse side of CuII/I@CMC-PANI film; SEM images (**c**) and EDS data (**d**) of its back side; and histogram of particle size (**g**).

SEM and EDS were carried out in order to study the morphology and components of the CuII/I@CMC-PANI film. The SEM images show a smooth surface for the obverse side (Figure 4a) and a rough surface for the back side (Figure 4c). It is worth noting that by increasing the magnification, spherical nanoparticles can be observed (Figure 4e,f), which may be attributed to the uniformly distributed copper oxides loaded in the film. The particle size histogram (Figure 4g) shows that the average particle size is approximately 10.04 nm in diameter. The EDS images of the obverse and back sides of CuII/I@CMC-PANI are shown in Figure 4b,d. EDS clearly showed the presence of the nonmetallic elements C,

N, and O, and the metallic element Cu in the dip catalyst. Significantly, the N content of the obverse side of the film (Figure 4b) is much higher than that of the back side (Figure 4d). This observation matched very well with the finding obtained from FT-IR (Figure 1), which illustrated that PANI mostly exists on the obverse side of the dip catalyst. The elemental mapping images (Figure 5), coupled with SEM, evidenced that the C, N, O, and Cu elements distributed throughout the catalyst in a homogeneous manner. The uniform distribution of Cu makes the catalyst work steadily.

**Figure 5.** SEM corresponding elemental mapping images of CuII/I@CMC-PANI film.

To investigate the thermal behavior of the CuII/I@CMC-PANI film, TGA and a corresponding DTG analysis of CMC-Na, PANI, and the CuII/I@CMC-PANI film were performed, and the results are displayed in Figure 6. Below 100 ◦C, all the samples (Figure 6a–c) showed a slight mass loss, which can be attributed to the release of adsorbed moisture and volatile impurities. After that, CMC-Na (Figure 6a) presented a sharp mass loss at around 290 ◦C, which corresponds to the decomposition of its glucose-unit chain and side carboxylic groups [46]. PANI (Figure 6b) exhibited two sharp decreases in mass at around 253 ◦C and 522 ◦C, which may be caused by the deprotonation of PANI and decomposition of the backbone units of PANI, respectively [30,47]. In the curve of the dip catalyst (Figure 6c), a mass loss in the temperature range of 198–400 ◦C appeared. This may account for the combined influence of the decomposition of CMC and PANI chains. This result indicated that the dip catalyst is stable up to nearly 200 ◦C, and that it is applicable for further A<sup>3</sup> reactions.

**Figure 6.** The TGA and DTG curves of CMC (**a**), PANI (**b**) and CuII/I@CMC-PANI film (**c**).

#### *3.2. Application of CuII/I@CMC-PANI Dip Catalyst in Three-Component A<sup>3</sup> Coupling Reactions*

First, the optimal reaction conditions for A<sup>3</sup> reactions were explored in the presence of the CuII/I@CMC-PANI dip catalyst (Table 1). Morpholine (1.2 mmol), *p*-chlorobenzaldehyde (1.0 mmol), and phenylacetylene (1.5 mmol) were selected as the model substrates. Initially, different solvents, including H2O, DMSO, DMF, CH3CN, EtOH, *n*-BuOH, and toluene, were screened to assess efficiency. It was found that the product yields increased with the decrease in solvent polarity. The highest yield was obtained when toluene was used as the solvent (Table 1, entry 7). Subsequently, to establish the fact that copper in the dip catalyst plays a key role in the A<sup>3</sup> reaction, the model reaction was performed in toluene at 110 ◦C in the absence of a catalyst, and in the presence of 1.8 mol% and 2.7 mol% of Cu in the catalyst, the product yields obtained were 0%, 93%, and 97% (Table 1, entries 7–9), respectively. When further increasing the dose of the catalyst to 3.6 mol%, no significant elevation in the product yield was observed (Table 1, entry 10). These results suggested that copper is essential for this A<sup>3</sup> model reaction, and 2.7 mol% of Cu is the optimal amount for the model reaction. Finally, the reaction temperature was explored, and it was found that decreasing the temperature from 110 ◦C to 90 ◦C, and even to 70 ◦C, had a considerable negative impact on the product yields (Table 1, entries 11–12). Therefore, it was concluded that the optimal condition involved morpholine (1.2 mmol), *p*-chlorobenzaldehyde (1.0 mmol), phenylacetylene (1.5 mmol), and the CuII/I@CMC-PANI dip catalyst (2.7 mol% of Cu) in toluene at 110 ◦C.



a Reaction conditions: *p*-chlorobenzaldehyde (1.0 mmol), morpholine (1.2 mmol), phenylacetylene (1.5 mmol) and solvent (2 mL). b Isolated yields. c No reaction. d Observed by TLC.

Next, with the optimal reaction condition in hand, the substrate scope of the reaction was examined (Table 2). Aryl aldehydes, bearing both electron-withdrawing and electrondonating groups, proceeded well to afford excellent yields (Table 2, entries 1, 3, 4, and 6), while salicylaldehyde was difficult to conduct the reaction with (Table 2, entry 5), due to the intramolecular H-bond, which improves the stability of its aldehyde group. Phenylacetylene, with electron-withdrawing groups on its aromatic ring, afforded lower yields, due to the fact that this group reduces its nucleophilic activity (Table 2, entries 7–10). Because it is hard to form a Cu-alkyne intermediate with aliphatic alkyne, a trace product was observed when using aliphatic alkyne as a substrate (Table 2, entry 11). As the imine

intermediate formed, aniline afforded no desired product (Table 2, entry 15). Unfortunately, aliphatic aldehydes afforded dissatisfactory yields (Table 2, entries 16–17), due to their low reactivity.

**Table 2.** A<sup>3</sup> coupling reactions catalyzed by CuII/I@CMC-PANI film to synthesize a variety of propargylamines a.


a Reaction conditions: aldehyde (1.0 mmol), amine (1.2 mmol), alkyne (1.5 mmol), CuII/I@CMC-PANI film (2.7 mol% of Cu), toluene (2 mL), at 110 ◦C. b All yields are isolated. c Observed by TLC. d No product, and generated imine was observed by GC-MS.

Furthermore, the recyclability and reusability of the CuII/I@CMC-PANI film for the A<sup>3</sup> model reaction was assessed. As shown in Scheme 3, the film could be recycled and reused successfully for up to six consecutive cycles, without significant losses in its activity. The Cu content, as measured by ICP-AES, in the recovered catalyst after two cycles was 1.705 mmol/g, which is slightly lower than that of 1.805 mmol/g in the fresh catalyst. Thus, to further investigate the Cu leaching of the catalyst in the A<sup>3</sup> reaction, a hot filtration test was performed. The model A<sup>3</sup> reaction was carried out at 110 ◦C for 1 h (36% conversion), and then the dip catalyst was picked up. The remaining mixture was further stirred for 5 h without the catalyst and a slight increase in conversation (36% to 50%) was observed, indeed suggesting that there was a small amount of Cu species leached out from the catalyst into the reaction mixture, which is consistent with the result of the ICP-AES analysis.

**Scheme 3.** Reusability of CuII/I@CMC-PANI dip catalyst in model A<sup>3</sup> reaction a. a Reaction conditions: *p*-chlorobenzaldehyde (1.0 mmol), morpholine (1.2 mmol), phenylacetylene (1.5 mmol), CuII/I@CMC-PANI dip catalyst (2.7 mol% of Cu), toluene (2 mL), at 110 ◦C. b Isolated yields. c Reacted for 6 h. d Reacted for 10 h.
