*3.5. Powder XRD Patterns*

As shown in Figure S3 (Supplementary Materials), the experimental PXRD patterns of **1**–**3** were all consistent with the simulated patterns obtained from single-crystal data, which confirm the purities of the samples. The differences in the intensities were attributable to the preferred orientations.

#### *3.6. IR Spectra*

As shown in Figure S4 (Supplementary Materials), the IR spectra of **1**–**3** show a series of similar absorption bands ranging from 4000–400 cm<sup>−</sup>1. The wide absorption bands from 3528 to 3134 cm−<sup>1</sup> are assigned to the stretching vibrations of the –OH, –CH2, and –NH2 groups. The sharp absorption peaks from 3005 to 2817 cm−<sup>1</sup> are the stretching vibrations of the –CH2 and –NH2 groups. The peaks ranging from 1652–1363 cm−<sup>1</sup> are the characteristic peaks of the bending vibrations of –NH2 and –CH2 groups in **1**–**3** and the carboxylate groups of the carboxylate ligands in **2**–**3**. Four intense characteristic peaks of *v*(P–O), *v*(W–Ot), *v*(W–Ob), and *v*(W–Oc) of the Keggin-fragments are observed at 1039, 941, 842, 796, and 716 cm−<sup>1</sup> for **1**, 1033, 935, 841, 796, and 715 cm−<sup>1</sup> for **2**, and 1037, 943, 848, 796, and 710 cm−<sup>1</sup> for **3**, respectively.
