The catalytic activity of Au-polyCAT was examined in the context of the intramolecular ring closing of alleneol 3 to form furan 4 (Fig. ). A solution of 3 in CDCl3 (0.05 M) containing tetrakis(trimethylsilyl)silane as an internal standard was added to a 2 mL reaction solution containing a 400 mg Au-polyCAT gel (0.016 mmol Au-CL, 20 mol% relative to alleneol 3). After 48 h, ~90% conversion of 3 to 4 was observed by 1 H NMR spectroscopy (Fig. ). Moreover, the Au-polyCAT was cycled through 7 rounds of the same reaction without loss of activity and achieved 60% conversion after 10 cycles giving a TON of 41. By contrast, and as expected based on the work of Reek and colleagues, the reaction reached only 20% conversion when Au-CL was used as the catalyst (Fig. ), supporting the presence of well-assembled MOC junctions within Au-polyCAT. A key potential advantage of the polyCAT system is that through decoupling of the catalyst environment from the polymer support, it could enable catalytic transformations in solvents or conditions where the catalysts are not otherwise compatible. For example, Au-CL and Au-MOC are not soluble in water; however, due to the polar nature of PEG-PL, Au-polyCAT swells extensively (swelling ratio of 4.4 in D2O). As a result, Au-polyCAT outperformed Au-CL and Au-MOC in the cyclization of 5 to 6 in D2O (Fig. ), achieving 96% conversion in 8 h compared to 1% for Au-CL and 21% for Au-MOC (Fig. . While water-soluble gold(I) N-heterocyclic carbene and triphenylphosphine complexes have been reported for analogous cyclization reactions, catalyst recovery is challenging and has not been demonstrated for these homogeneous systems. By contrast, Au-polyCAT could be cycled at least 12 times, maintaining >94% (Fig. ) conversion and achieving a TON of 115. An increase in swelling and a 3-fold decrease in G′ was observed after these 12 cycles, suggesting some mechanical wearing of the material (Fig. ). To rule out catalyst leeching from the network due to gel degradation over these 12 cycles, substrate 4 was added to the supernatant of an Au-polyCAT-catalyzed reaction; after 8 h, <5% of 4 had cyclized to the lactone product (<15% after 24 h), indicating that the catalytic activity of gel degradation products is negligible. Altogether, these results highlight the potential to use polyCATs under conditions that are not compatible with homogeneous catalyst analogues (e.g., aqueous conditions wherein the catalysts are not soluble) and for facile catalyst recycling.