The rate constants (Figure ) were determined by fitting the data from Figure to a pseudofirst-order kinetic model concerning the concentration of 4-NP (Figure ). The turnover frequencies (TOF) for investigated samples (Figure ) were calculated using the linear range of substrate conversion at the beginning of the reaction, taking the end of the induction period as time 0. The TOF value is given with respect to one atom of Au, hence its unit is h -1 atomAu -1 . The benchmark sample Au10 has a TOF value of 3888 h -1 atomAu -1 , which is comparable to the value reported in the literature. Notably, the K,NaPHI2 catalyst exhibits a remarkably high TOF value of 6149 h -1 atomAu -1 , which is superior to TOFs of the benchmark Au10 (3888 h -1 ), KMel0.3 (4464 h -1 ), KCya0.3 (3498 h -1 atomAu -1 ), and KCA0.3 (2276 h -1 atomAu -1 ), as shown in Figure . The sample KCA0.3, comprising a triazine-based stabilizer, possesses the lowest TOF value, which is likely because KCA leads to larger Au NPs. Moreover, among the proposed stabilizers, KCA has the highest density of negatively charged groups where all carbons bear one negatively charged O -group. Therefore, the AuNPs surface is likely crowded by the stabilizing molecules, partially blocking the surface catalytic activity. The outstanding catalytic performance of the Au NPs stabilized by K,Na-PHI can be, in our view, attributed to two main effects. Firstly, K,Na-PHI favours the formation of ultrasmall Au NPs, allowing for higher specific surface area and more optimal utilization of Au atoms. Secondly, the flexible and extended framework structure of the polymeric K,Na-PHI enables both effective stabilization and -at the same timefacilitates the diffusion of reactants and products to and from the surface of gold NPs. ), and 2.5 mL distilled water were mixed into a cuvette at ambient conditions. Then, the UV-Vis spectrum was recorded, followed by the addition of 0.025 mL of AuNP catalyst (1.14 mg L -1 ) and shaking quickly the cuvette before recording the subsequent spectra.