Ce no3 3

All Gd/CeO₂ catalysts were prepared by a modified hydrothermal method.^[43] Briefly, 0.09 mmol of Ce(NO₃)₃ (Sigma‐Aldrich, USA) was dissolved in 30 mL of deionized water in polytetrafluoroethylene vessels. After the complete dissolution of cerium nitrate, 0.005 mmol of Gd(NO₃)₃ (Sigma‐Aldrich, USA), dissolved in 10 mL of deionized water, was added to the Ce(NO₃)₃ solution. Under magnetic stirring, ammonium hydroxide (0.1 m, Sigma‐Aldrich, USA) was added dropwise to complete the precipitation (final pH = 10) and stirred at 160 °C for 24 h. The products were collected by centrifugation, washed with deionized water, and redispersed in water to form a 1.0 mg mL⁻¹ solution. Then, 20 mL of an aqueous solution of polyvinylpyrrolidone (0.5 g, PVP 55 000 Da, Sigma‐Aldrich, USA) was added to 10 mL of the Gd/CeO₂ solution and stirred for 24 h. The PVP‐modified Gd/CeO₂ was finally separated by centrifugation at 12000 rpm for 30 min, washed with pure water three times, and dispersed in pure water for future use.

Rhodamine B, ethylene diamine, exo-3,6-Epoxy-1,2,3,6-tetrahydrophthalic anhydride, triethyl amine and Hoveyda-Grubbs 2nd generation catalyst (HG2). All metal nitrate salts such as NaNO₃, KNO₃, Mg(NO₃)₂, Al(NO₃)₃, Cu(NO₃)₂, Zn(NO₃)₂, Co(NO₃)₂, Ni(NO₃)₂, Zr(NO₃)₃, Ce(NO₃)₃, La(NO₃)₃, Cd(NO₃)₂, Hg(NO₃)₂, Pb(NO₃)₂ and LiNO₃ were purchased from Sigma-Aldrich. Solvents were purified by standard techniques prior to use for all synthesis. ¹H NMR and ¹³C NMR spectra were recorded on AV 400 MHz Bruker or AV 600 MHz Bruker NMR spectrometer using CDCl₃ and CD₃CN as the solvent at 298 K. Tetra methyl silane (TMS) as an internal standard for ¹H NMR. GPC analysis were carried out using a Viscotek GPC Max VE 2001 instrument with Viscotek TDA 302 tripe array detector Viscotek Org Guard column. UV–Vis spectra were recorded on a Perkin Elmer Lambda 950 UV–Vis spectrometer, using quartz cells of 10 mm path length at 273 K. Fluorescence emission spectra were recorded on Cary eclipse fluorescence spectrophotometer, using quartz cells of 10 mm path length at 273 K. IR spectra on Perkin Elmer FT-IR spectrometer, DSC spectra on Perkin Elmer Jade DSC and TGA on Perkin Elmer Pyris 6 were recorded.