Covalent Triazine Frameworks with Defective Accumulation Sites: Exceptionally Modulated Electronic Structure for Solar-Driven Oxidative Activation of Peroxymonosulfate

Abstract

Precisely tailoring the electronic structure and surface chemistry of metal-free covalent triazine frameworks (CTFs) for efficient photoactivation of oxyanions is environmentally desirable but still challenging. Of interest to us in this work was to construct artificial defective accumulation sites into a CTF network (CTF-SD x ) to synchronously modulate both thermodynamic (e.g., band structure) and kinetic (e.g., charge separation/transfer/utilization and surface adsorption) behaviors and probe how the transformation affected the subsequent activation mechanism of peroxymonosulfate (PMS). With the incorporation of terminal cyano (−CN) groups and boron (B) dopants, the delocalized CTF-SD underwent a narrowed electronic energy gap for increased optical absorption as well as a downshifted valence band position for enhanced oxidation capacity. Moreover, the localized charge accumulation regions induced by the electron-withdrawing −CN groups facilitated the exciton dissociation process, while the adjacent electron-deficient areas enabled strong affinity toward PMS molecules. All of these merits impelled the photoactivation reaction with PMS, and a 15-fold enhancement of bisphenol-A (BPA) removal was found in the CTF-SD2/PMS/vis system compared with the corresponding pristine CTF system. Mechanistic investigations demonstrated that this system decomposed organics primarily through a singlet oxygen-mediated nonradical process, which originated from PMS oxidative activation over photoinduced holes initiated by an electron transfer process, thereby opening a new avenue for designing an efficient PMS activation strategy for the selective oxidation of organic pollutants.

Fluorinated Defect-Engineered Acetylenic Polymers with Separated Active Centers for Switching the Photosensitized Activation Pathway of Peroxymonosulfate

“…This efficient pollutant elimination performance highlights the general applicability of PTEB-F 15 in oxidizing a wide range of refractory contaminants by using PMS as the oxidant. Notably, the degradation of CBZ achieved only 75%, primarily due to the electron-withdrawing groups, CONH 2 , within the CBZ molecules making them less susceptible to the electrophilic attack of 1 O 2 , thereby leading to relative sluggish elimination efficiency in the 1 O 2 -dominated degradation system. − …”

Donor–acceptor sp2covalent organic frameworks for photocatalytic H2O2production and tandem bisphenol-A degradation

“…Such high VBM values further indicated the suitability of the COFs to oxidize BPA into degradation products (0.77 V, vs. NHE at pH = 7). 36…”

Internal Electric Field and Adsorption Effect Synergistically Boost Carbon Dioxide Conversion on Cadmium Sulfide@Covalent Triazine Frameworks Core–Shell Photocatalyst

“…[ 60 ] The latter corresponds to the N─C═N bond of the triazine rings. [ 61,62 ] Moreover, the N 1s spectrum of pure CTF‐HUST‐1, shown in Figure 7d, can be resolved into two peaks. The stronger peak (398.92 eV) is attributed to pyridinic N or triazine N in the triazine rings, and the other peak, with a binding energy of 399.95 eV, is associated with pyrrolic N originating from partial decomposition of CTF‐HUST‐1.…”