## 5 Conclusions  
In summary, this paper describes a convenient approach to polystyrene-supported TBTA-Cu(I) catalysts suitable for continuous-flow CuAAC applications. In our opinion, the main merit of the synthetic route disclosed herein is the possibility of its easy and affordable scale-up. This advantage concerns not only the synthesis of the functional monomer **3**, but also its covalent immobilization within the insoluble polymer network through robust radical-copolymerization with cheap divinylbenzene. Irrespective of the technique and conditions adopted for the purpose, either suspension or mold-copolymerization, the resulting highly cross-linked resins (**P7** and **M7**, respectively) have been shown to possess swelling and textural properties that made them fit for applications in batch and in flow. In this regard, it is worth noting that in several circumstances, **P7** and **M7** were used in liquid media with a high volume fraction of MeOH or H\({}_{2}\)O, which are two thermodynamically bad solvents for the polystyrene chains. The good results that were nonetheless observed under these conditions demonstrate the suitability of the macromolecular structure (most likely, the high \(S_{\mathrm{BET}}\) values) of the supported ligands developed in this work. After charging **P7** and **M7** with Cu(I) or Cu(II) salts (and, in the case of the latter, reduction with sodium L-ascorbate), the supported complexes showed excellent activity in the copper-catalyzed Huisgen cycloaddition of azides to polar alkyne substrates. Following an initial screening in batch, most of these CuAAC reactions were performed in continuous-flow reactors, either of the monolithic or packed-bed type. In general, good results were obtained with both reactor architectures, with the monolithic ones showing better specific activity, but also some propensity towards clogging. The CuAAC runs in batch demonstrated the possibility to reach high conversions at room temperature, with calculated space-time yields that, in some cases, exceeded 240 g L-1 h-1. Moreover, at least in the CuAAC processes that led to mono-triazole products, the catalytic flow devices showed a reasonable durability. In some examples, this allowed accumulated turnover numbers larger than 400 with respect to the amount of copper initially loaded onto the functional resin to be easily attained. In view of the results summarized above, work is currently aimed at increasing the reactivity of the less polar alkyne substrates, further reducing metal leaching, and improving the permeability of the monolithic reactors. Progress in these directions will be reported in due course. **Supplementary Materials:** The following are available online at [[http://www.mdpi.com/2073-4344/10/4/434/s1](http://www.mdpi.com/2073-4344/10/4/434/s1)]([http://www.mdpi.com/2073-4344/10/4/434/s1](http://www.mdpi.com/2073-4344/10/4/434/s1)): Additional experimental details; NMR spectra of **3**, **4**, **6**, and of the 1,2,3-triazole products from the CuAAC runs: typical GC-MS chromatogram for the benchmark CuAAC reaction; Figure S1: Schematic of the continuous-flow reactor used in the CuAAC runs; Figure S2: Appearance and SEM images of the resin materials; Figure S3: FT-IR spectra of **P7** and **M7**; Figure S4: N\({}_{2}\) adsorption-desorption isotherms of **P7**; Figure S5: N\({}_{2}\) adsorption-desorption isotherms of **M7**; Figure S6: N\({}_{2}\) adsorption-desorption isotherms of **M7**-Cu(OTf)\({}_{2}\); Figure S7: EDS spectra and mapping of the Cu content in **M7**-Cu(OTf)\({}_{2}\). **Author Contributions:** Conceptualization, A.M.; validation, G.A., D.S., and A.M.; investigation, A.P., G.A., M.P., A.L., M.C., F.O., M.M., D.S., and A.M.; resources, A.M. and C.E. ; writing--original draft preparation, A.M.; writing--review and editing, A.M. and C.E. ; visualization, M.M. ; supervision, A.M.; project administration, A.M.; funding acquisition, C.E. and A.M. All authors have read and agreed to the published version of the manuscript.