## Discussion
### Preparation of the TBTA Monomer and Supported Catalysts
Moreover, cost considerations led to disregard routes based on the grafting of TBTA units on commercial macroporous resins, in favor of the co-polymerization of the TBTA monomer **3** with technical divinylbenzene (DVB) as a cheap cross-linking agent. Even though the preparation of **3** has been reported in the literature [20; 21], at the beginning of this work, we set out to find a more convenient and scalable route for its synthesis. In particular, the goal was to avoid the use of expensive reagents and multiple chromatographic purification steps required by the published preparations of the TBTA monomer **3**, or its direct precursor **4**[17; 20; 21; 22; 23]. After exploring alternative routes, a straightforward procedure was identified for converting dipropargylamine (**5**) into **3**, in three high-yielding steps (Scheme 1). The key point of the whole sequence was the alkylation of the intermediate **6** with propargyl bromide that, after some optimization work, was found to proceed much better than anticipated [39]. This allowed **4** to be obtained in a nearly quantitative yield by simple precipitation of the crude product with water and subsequent recrystallization from AcOEt. Thanks to the high yield in the initial CuAAC reaction between **5** and benzylazide, the whole reaction sequence could be scaled-up in an effortless manner to provide 11.5 g of pure **4**. The subsequent CuAAC reaction between **4** and 4-azidomethylstyrene, followed by the removal of copper species through aqueous ammonia work-up, afforded the monomer **3** in an essentially quantitative yield. Because the NMR purity of **3** appeared to be high, the freshly prepared monomer was used directly in the crude form. Having achieved the preparation of **3** through a high-yielding and chromatography-free synthetic sequence, its immobilization in styrene-type resins could be explored. This aim was pursued by following two alternative routes: (_a_) The co-polymerization of **3** and DVB in a poly(vinyl alcohol)-stabilized aqueous suspension, to give resin beads **P7**, and (_b_) Frechet-type co-polymerization of the same monomers inside stainless-steel tubular molds [40; 41; 42; 43], which afforded the monolithic resins **M7**. As confirmed by the evidence detailed in the Results section, both approaches proved effective (\(>\)87% yield) towards the goal of high incorporation of the functional monomer in the cross-linked polymeric network. At the same time, and in spite of the identical co-monomer composition (**3**:DVB = 10:90), differences were observed in the swelling and morphological properties of the various resins and in their ability to adsorb Cu(I) or Cu(II) salts. Overall, the swelling ratios of **M7** and **P7** in THF (_sr_ = 1.3 and _sr_ = 1.5, respectively) and the SEM images suggest a more rigid polymer architecture for the monoliths than for the resin beads. Concerning the specific surface area deduced from N\({}_{2}\) adsorption measurements (**M7**: \(S_{\text{BET}}\) = 435 m\({}^{2}\) g\({}^{-1}\); **P7**: \(S_{\text{BET}}\) = 273 m\({}^{2}\) g\({}^{-1}\)), the results look somewhat counterintuitive in view of the use of a larger amount of 1-dodecanol under the mold polymerization conditions. In fact, being a bad solvent for the growing polystyrene chains, this porogenic agent was expected to reduce \(S_{\text{BET}}\) as a consequence of the shift of the porosity distribution towards the macroporc domain [44]. Therefore, the observation of an experimental trend, which is the opposite of the predicted one, points to the occurrence of additional phenomena, possibly linked to the presence of the aqueous dispersing phase during the suspension polymerization process. Both **P7** and **M7** demonstrated a good to excellent ability to adsorb CuCl or CuX\({}_{2}\) salts (X = OTf or 1/2 SO\({}_{4}\)) dissolved in suitable solvents.