# Naphthalene-Based Polymers as Catalytic Supports for Suzuki Cross-Coupling
## 2 Results
### Characterization of the Catalysts  
Synthesized and reduced Pd-containing catalysts (1%-Pd/NA60-R, 1%-Pd/NA120-R, 1%-Pd/NNA120-R, 1%-Pd/SNA120-R, 1%-Pd/NL60-R) were analyzed by DRIFTS in order to find out if any changes occurred during the treatment with NaBH\({}_{4}\). Normalized IR-spectra of the catalysts 1%-Pd/NA120-R and 1%-Pd/NL60-R in comparison with the IR-spectra of corresponding polymers are shown in Figure 9.  
It can be seen that the treatment with NaBH\({}_{4}\) had no visual effect on the polymers' structure. The same was observed for 1%-Pd/NA60-R. The increase in intensity of the absorption bands at 2924 cm\({}^{-1}\) (which corresponds to CH\({}_{2}\)-groups), at about 3500 cm\({}^{-1}\) (which corresponds to OH-groups), and at 1730 cm\({}^{-1}\) (which likely corresponds to ester groups Ar-C(O)-O-R) can be due to the procedure of catalysts' preparation and reduction, i.e., the THF and the product of its hydrolysis could remain in the polymer pores. Figure 8: High-resolution XPS spectra of N 1s in NNA120 (**a**) and S 2p in SNA120 (**b**). In the IR-spectrum of 1%-Pd/NNA120-R (Figure 9(b)), the absorption bands are the same as for SNA120. However, similarly to 1%-Pd/NA120-R and 1%-Pd/NLR60-R, the intensity of the absorption bands corresponding to CH\({}_{2}\)-, OH-, and ester groups increased. This could be explained by the strong adsorption of solvents (THF) on the polymer. In the case of 1%-Pd/NNA120-R (Figure 9(a)), there were some noticeable differences in the corresponding IR-spectra: a new band at ca. 3390 cm\({}^{-1}\) occurred that can be attributed to the stretching vibrations of N-H forming hydrogen bonds. Additionally, the absorption band at 1619 cm\({}^{-1}\) appeared, which can be referred to deformation vibrations of N-H of amino-groups. Thus, during the formation of Pd NPs, partial reduction of the nitro-groups of NNA120 occurred. STEM was carried out for the reduced Pd-containing catalysts (1%-Pd/NA60-R, 1%-Pd/NA120-R, 1%-Pd/NNA120-R, 1%-Pd/SNA120-R, and 1%-Pd/NL60-R). Figure 11 represents the HAADF STEM image of 1%-Pd/NA60-R and the corresponding EDX mapping. As can be seen, a non-uniform distribution of palladium occurred,  
Figure 10: Comparison of the normalized IR-spectra: NNA120 and 1%-Pd/NNA120-R (**a**); SNA120 and 1%-Pd/SNA120-R (**b**). Figure 9: Comparison of the normalized IR-spectra: NA120 and 1%-Pd/NA120-R (**a**); NL60 and 1%-Pd/NL60-R (**b**). which was likely due to microporosity along with the relatively high hydrophobicity of NA60. Huge aggregates of polydisperse Pd NPs with a mean diameter of 16.5 \(\pm\) 7.3 nm were formed after the reduction. 1%-Pd/NA120-R (Figure 12a) as well as 1%-Pd/NL60-R (Figure 12b) revealed more uniform Pd distribution as compared with 1%-Pd/NA60-R and lower diameters of Pd NPs (12.1 \(\pm\) 4.1 nm for 1%-Pd/NA120-R and 9.9 \(\pm\) 2.6 nm for 1%-Pd/NL60-R). In the case of 1%-Pd/NL60-R, the smaller diameter and better distribution of Pd NPs can be due to the relatively higher oxygen content (6.9 at.%) as compared with 1%-Pd/NA120-R (4.1 at.%). The smallest Pd NPs (3.0 \(\pm\) 1.3 nm) with the narrowest NP size distribution were found in the case of 1%-Pd/NNA120-R (Figure 12c) in spite of the meso-macroporous structure of the polymer (NNA120). In the case of 1%-Pd/SNA120-R, Pd NPs with a mean diameter of 7.5 \(\pm\) 3.3 nm and a broad size distribution were formed after the reduction of Pd acetate in meso-macroporous SNA120 (Figure 12d), which were still smaller as compared with NPs formed in NA120-R and NL60-R. Some correlation can also be found between the oxygen content on the surface of initial polymers and the mean diameter of Pd NPs formed after the reduction with sodium borohydride (Figure 13). Figure 11: HAADF STEM image (scale 300 nm) of 1%-Pd/NA60-R(**a**) and EDX mapping of C (**b**), Pd (**c**), Na (**d**), Cl (**e**), and O (**f**). Figure 12: Bright-field STEM images of the reduced samples1%-Pd/NA120-R (**a**), 1%-Pd/NL60-R (**b**), 1%-Pd/SNA120-R (**d**) and HAADF STEM image of 1%-Pd/NNA120-R (**c**) (scale 50 nm).