## 3 Results and Discussion
### Catalytic Activity  
#### 3.8.1 Effect of PdAS Loading  
The C-C coupling reaction of I-Ph with MA to produce MCIN was used to evaluate the catalytic activity of the mesoporous PdAS(x)-MA resins. Several experimental conditions have been reported for such a transformation, including a reaction temperature of 80-120 \({}^{\circ}\)C, different solvents (H\({}_{2}\)O, toluene, dimethylacetamide, DMF, and EtOH), and a range of bases (K\({}_{2}\)CO\({}_{3}\), Na\({}_{2}\)CO\({}_{3}\), Na(CH\({}_{3}\)CO\({}_{2}\)), pyrrolidine, and TEA) [59; 60; 61; 62; 63; 64]. Thus, to evaluate the suitability of the PdAS(x)-MA resins as catalysts for the selected C-C coupling reaction, their catalytic activities were determined at 120 \({}^{\circ}\)C using TEA as the base and DMF as the solvent. A control experiment was also carried out in the absence of a catalyst over 10 h, and no I-Ph conversion or product formation was observed. In addition, the homogeneous Pd(CH\({}_{3}\)CO\({}_{2}\))\({}_{2}\) and Pd-SALOPHEN catalysts were evaluated under the same reaction conditions for comparison. Figure 7a shows the I-Ph conversion-time profiles for the homogeneous Pd(CH\({}_{3}\)CO\({}_{2}\))\({}_{2}\) and Pd-SALOPHEN catalysts, and for the heterogeneous PdAS(x)-MA resins, where the catalytic activity decreased in the order of: Pd(CH\({}_{3}\)CO\({}_{2}\))\({}_{2}\)\(\sim\) PdAS(10)-MA \(>>\) PdAS(5)-MA \(\sim\) Pd-SALOPHEN \(>\) PdAS(2)-MA \(>\) PdAS(1)-MA. In addition, the obtained 100% selectivity toward the desired MCIN product indicated the absence of geminal coupling (see Scheme 1). This behavior has been attributed to the presence of TEA, which prevents the competitive I-Ph homo-coupling reaction taking place [65]. The time required to reach an iso-conversion of 5% I-Ph conversion as estimated from the exponential trend curves of the PdAS(x)-MA catalysts (Figure S3) indicates the same dependence on the immobilized PdAS content. Figure 7: Kinetic profiles for the coupling of I-Ph with methyl acrylate to produce methyl cinnamate (MCIN) using the Pd-based catalysts. (**a**) Open square: Pd(CH\({}_{3}\)CO\({}_{2}\))\({}_{2}\); open triangle: Pd-SALOPHEN, fill circle: PdAS(1)-MA, fill diamond: PdAS(2)-MA, fill pentagon: PdAS(5)-MA, and fill inverse triangle: PdAS(10)-MA. (**b**) Hg(0) poisoning test for Pd-SALOPHEN catalyst and (**c**) Hg(0) poisoning test for Pd(CH\({}_{3}\)CO\({}_{2}\))\({}_{2}\) catalyst. We found that a large I-Ph conversion was obtained for both Pd(CH\({}_{3}\)CO\({}_{2}\))\({}_{2}\) and PdAS(10)-MA, with the maximum conversion being reached after 30 min. Indeed, the catalytic results summarized in Table 3 indicate the dependence of the I-Ph conversion on the PdAS(x) content. This behavior can be explained by considering the catalytic mechanism of the Pd-catalyzed C-C cross-coupling reaction. The accepted catalytic cycle for the Heck reaction proposed by [PERSON] is summarized in Scheme 2 [7]. The superior catalytic activity exhibited by Pd(CH\({}_{3}\)CO\({}_{2}\))\({}_{2}\) was attributed to the formation of atomic Pd particles during the catalytic transformation. Indeed, a study by [PERSON] supported the formation of such particles, and this was explained by the fact that in the coupling of I-Ph with electron withdrawing olefins, alkene insertion is the rate determining step. When I-Ph is no longer present in the reaction media, Pd colloid formation takes place spontaneously [66]. This behavior was confirmed in our experiments by the detection of metallic Pd nano- and micro-particles after to the Heck reaction, as shown in Figure 8a. Figure 8: _Cont._