Revisiting Nitrogen Species in Covalent Triazine Frameworks

Abstract

Covalent triazine frameworks (CTFs) are porous organic materials promising for applications in catalysis and separation due to their high stability, adjustable porosity, and intrinsic nitrogen functionalities. CTFs are prepared by ionothermal trimerization of aromatic nitriles; however, multiple side reactions also occur under synthesis conditions, and their influence on the material properties is still poorly described. Here we report the systematic characterization of nitrogen in CTFs using X-ray photoelectron spectroscopy. With the use of model compounds, we could distinguish several types of nitrogen species. By combining these data with textural properties, we unravel the influence that the reaction temperature, the catalyst, and the monomer structure and composition have on the properties of the resulting CTF materials.

Evaluation of the Environmental Impact and Efficiency of N-Doping Strategies in the Synthesis of Carbon Dots

“…The contribution of C=O/C=N groups differs for all samples, being quite important for samples 1 (CA-urea) and 4 (CA-acetonitrile) with 36 and 32% respectively, moderate in sample 2 with 23% and relatively small in CDs 3 (CA-DMF) with only 12%. CDs 5 (CA-pyridine) presents a different peak deconvolution around 289 eV as it could be split into two small peaks, with contributions attributed to C=O/C=N at 288.5 eV and to carboxylate (O-C=O) or amide carbon (N-C=O) at 289.3 eV [48,[55][56][57][58], with 6% and 8% respectively thus giving an overall contribution of 14% for the peak at 289 eV. The presence of π-conjugated groups (C=O, C=N, O-C=O and N-C=O) has a potential impact on the photoluminescence efficiency of CDs [59][60][61][62].…”

“…The two first samples present dominant contributions from pyrrolic N group (~89%) and small contribution from graphitic N group (~11%). Additionally, another peak is found in sample 3 at~402 eV, which can be attributed to N-O bond [57,64]. Due to the quite small amount of N-doping (0.6 and 1.6%), the N 1s spectra of samples 4 and 5 were not analyzed.…”

Covalently Conjugated Gold–Porphyrin Nanostructures

“…A careful fitting of the experimental profile required five Gaussian components centered at 397.9, 398.6, 399.5, 399.9, and 400.4 eV. The component at 397.9 eV is assigned to the ionization of the two non-protonated imine nitrogens of the porphyrin core, that at 398.6 eV to the six triazine ring nitrogen atoms, that at 399.5 eV is assigned to the four –NH 2 triazine substituents, that at 399.9 eV is assigned to the two protonated pyrrole nitrogens of the porphyrin core and to the two –NH- groups bound to the triazine moiety and, finally, that at 400.4 eV is consistent with the two O=C(Ar)-NH- amide functionalities [ 5 , 55 , 57 , 58 , 59 , 60 , 61 , 62 ].…”

Integration of an N‐Heterocyclic Carbene Precursor into a Covalent Triazine Framework for Organocatalysis

“…Deconvolution of the N 1 s spectra revealed the existence of pyridinic nitrogen with a binding energy (BE) of approximately 398.4 eV, which reflects nitrogen atoms from the triazine cores of the polymeric network . More importantly, the presence of imidazolium nitrogen atoms (BE≈401.7 eV, only one signal can be detected due to resonance) provided clear evidence of an (partially) intact structure bearing cationic imidazolium moieties . Interestingly, an additional signal at a BE of approximately 400.0 eV could be observed that most probably stems from a by‐product as a consequence of decomposition processes (see also Figure S13 in the Supporting Information for N 1 s XPS spectrum of the monomer and further explanation).…”

“…High‐resolution nitrogen N 1 s spectra were recorded to distinguish between the two nitrogen species, which should be present within the imid‐CTF (Figure b). Deconvolution of the N 1 s spectra revealed the existence of pyridinic nitrogen with a binding energy (BE) of approximately 398.4 eV, which reflects nitrogen atoms from the triazine cores of the polymeric network . More importantly, the presence of imidazolium nitrogen atoms (BE≈401.7 eV, only one signal can be detected due to resonance) provided clear evidence of an (partially) intact structure bearing cationic imidazolium moieties .…”