Supporting Information: Supplementary Figure 1. (a) TEM and (b) HRTEM image of the Pd nanocube seeds. Inset of (b): the FFT pattern. (c) Magnified image of the square region highlighted in (b).
Supplementary Figure 2. (a) Low- and (b) high-magnification TEM images, and (c) histogram of the size distributions of Pd nanocube seeds. (d) Low- and (e) high-resolution TEM images, and (f) histogram of the size distributions of as-prepared Pd nanocages after 1 hr of etching the Pd nanocube seeds.
Supplementary Figure 3. TEM images of a Pd nanocage obtained at three tilt angles of 0, 20, and 40. All scale bars are 5 nm. Simulated nanocage structures along with TEM images are shown above. From these images, the three-dimensional (3D) characteristics of Pd nanocages were unambiguously demonstrated.
Supplementary Figure 4. EDX spectrum of the as-prepared Pd nanocages after 1 hr etching of Pd nanocube seeds.
Supplementary Figure 5. HRTEM image of the Pd nanocage shows the single crystalline structure along the [100] axis, where {200} facets are resolved.
Supplementary Figure 6. An inverse FFT image corresponding to Fig. 4-c.
Supplementary Figure 7. FTIR spectra of CTAB crystals, and Pd nanocubes and Pd nanocages. Peak positions and widths of C-CH 2 asymmetric and symmetric stretching vibrations of the methylene chain of CTAB can be used to assess the nature of surfactant packing on solid surfaces. The lower vibrational frequency and the narrower bandwidth of the crystalline surfactant correspond to more ordered structures of the methylene chains of CTAB.
Supplementary Figure 8. (a) UV-Vis spectra of the supernatant before and after the etching treatment of Pd seeds. The UV-Vis spectrum of CTA + [PdX 4 ] 2- in octanol (116 µm) is also shown as control. (b) UV- Vis spectra of a series of CTA + [PdX 4 2- ] in the concentration from 0 to 180 mm in octanol. (c) Plots of the absorbance at 250 nm and 340 nm with the concentration of CTA + [PdX 4 2- ] in octanol.
Supplementary Figure 9. The effect of solvents on the shape evolution of 12 nm Pd seeds. Experiments were performed in (a) EG and (b) EG/octanol (1:1) solvents, respectively. All other conditions are the same with the one in Fig. 4.
Supplementary Figure 10. Typical 1 HNMR spectra of the products obtained from PhB(OH) 2 and iodotoluene via Suzuki coupling reaction catalyzed by Pd nanocages at 50 C temperature.
Supplementary Figure 11. Schematic illustration of the preparation of NovaSyn TGR resin-supported aryl iodide and its application for the three phase test. First, 4-iodobenzoic acid is conjugated with NovaSyn TGR resin 1 to produce the compound 2. Then, in the three phase test, if phenylboronic acid reacts with the compound 2 via the Suzuki coupling reaction in the presence of free Pd atoms or Pdorganic complexes as catalysts in solution, the compound 3 will be formed. If there are no homogeneous Pd active species in solution, this reaction will not be catalyzed and thus the compound 2 will remain unchanged. The product, whether compound 5 or compound 6, can be determined by GC MS after cleaving them from the resin. The compound 4 is a cleaved part of resin side.
Supplementary Figure 12. (a) Typical gas chromatogram for the final product after the three phase test and TFA cleavage (see Supplementary Fig. 11 for the reaction steps). The resin (0.01 mmol) was undergone the three phase test in the standard condition (0.6 mmol PhB(OH) 2, 0.3 mmol iodotoluene, 1 mmol K 2 CO 3, 10 µg Pd nanocages (0.03 mol%), 5 ml 80% ethanol aqueous solution, 50 C, 2 h). It should be noted that three phase tests for other samples, i.e., the sample without iodotoluene and another sample including iodobenzene (0.6 mmol PhB(OH) 2, 0.3 mmol iodobenzene, 1 mmol K 2 CO 3, 10 µg Pd nanocages (0.03 mol%), 5 ml 80% ethanol aqueous solution, 25 C, 2 h), show similar gas chromatogram. (b) Gas chromatogram of commercial biphenyl-4-carboxamide (6 in Supplementary Fig. 11). The peak at 5.03 min was assigned to biphenyl-4-carboxamide. (c) Mass spectrum of the 2.43 min peak of the chromatogram in (a). (d) Mass spectrum of the 4.01 min peak of the chromatogram in (a). Analysis of each spectrum confirms that (c) represents the dodecane internal standard, while (d) represents 4- iodobenzamide (5 in Supplementary Fig. 11). Lack of 5.03 min peak in (a) suggested that no resin-bound aryl iodide 2 was converted into biphenylamide (3 in Supplementary Fig. 11). These results indicate that no release and capture of active species (Pd atoms or Pd-organic complexes) occurs in the solution phase during the three phase tests, and the coupling reactions only take place on the nanoparticle surface.
Supplementary Figure 13. Typical 1 HNMR spectrum for the final product after the three phase test and TFA cleavage. The resin (0.01 mmol) was undergone the three phase test in the standard condition (0.6 mmol PhB(OH) 2, 0.3 mmol iodotoluene, 1 mmol K 2 CO 3, 10 µg Pd nanocages (0.03 mol%), 5 ml 80% ethanol aqueous solution, 50 C, 2 h). This spectrum supports that only unreacted reactant of aryl iodide (5 in Supplementary Fig. 11) was detected after cleaving bonds with the resin and no resin-bound aryl iodide (2 in Supplementary Fig. 11) was converted into the product of biphenylamide (3 in Supplementary Fig. 11).
Supplementary Figure 14. (a) Low- and (b) high-magnification TEM images, and (c) EDX of Au nanocube seeds. Inset of (b) is a selected-area electron diffraction (SAED) image of Au nanocubes that agrees with the diffraction pattern of Au crystals. (d) TEM images of Au nanocages after etching Au nanocubes following the same procedure used for Pd nanocage fabrication. Inset of (d) is a SAED image of Au nanocages. (e) (g) High magnification TEM images of a Au nanocage (highlighted with an arrow in (d)) obtained at different tilt angles of 0, 30, and 60 along y axis.
Supplementary Figure 15. 1 HNMR spectra of the products obtained from PhB(OH) 2 and iodobenzene via Suzuki coupling reaction catalyzed by Pd nanocages at room temperature.