Fig. 10. Structure analysis of Ir/AP-POPs. Atomically dispersed and stable Ir metal atoms are analyzed. (A) The solid-state 13C/CP-MAS NMR spectrum of the AP-POP suggests the presence of C O, C–N, and C–Ar groups. (B) The N 1s core level XPS spectrum of the AP-POP distinguishes N in the pyridinic and amide groups in the framework. (C) The UV-vis absorbance spectra of samples with and without Ir indicate the p–p* electron transition of the conjugated polymer and show the supported Ir single atoms result in a red-shift of absorption. (D) An SEM image shows the spherical particles morphology of the AP-POP. (E and F) HAADF-STEM images of fresh (E and F) used 1.25% Ir/AP-POP indicate only the atomically dispersed Ir species on the support, even after the CO₂ hydrogenation reaction. Reproduced from ref. 115 with permission of the publisher.