Triaminopyrimidine Based Porous Organic Polymers: Synthesis, Characterization and Catalytic Applications in One‐pot Room Temperature Synthesis of Dihydropyranopyranes

Shunmughanathan, Murugesan; Madankumar, Natarajan; Pitchumani, Kasi

doi:10.1002/slct.201803483

“…The TG-DSC curve ( Figure S3 ) and powder XRD patterns of i-POF are similar to other i-POF materials, particularly the related 2,4,6-triaminopyrimidine- and melamine- i-POFs, with the material being stable up to 300 °C [ 23 ] and its amorphous characteristics ( Figure 3 left) confirmed by the broad band at 22° observed in the powder XRD patterns. The corresponding d spacing value was 0.4 nm [ 8 , 22 , 23 , 30 ]. Scanning electron microscopy (SEM) ( Figure 3 —right) revealed aggregated particles of variable size with no defined morphology [ 20 , 23 ].…”

Section: Resultssupporting

confidence: 57%

“…It is also possible to observe N–H stretching at 3406 and 3230 cm −1 (free and hydrogen-bonded, respectively) and N–H bending at 1620 cm −1 . The bands at 1577 cm −1 and 1420 cm −1 correspond to pyrimidine ring C=N stretching and residual imine and C–N stretching, respectively [ 8 , 23 ].…”

Section: Resultsmentioning

confidence: 99%

“…The corresponding d spacing value was 0.4 nm [ 8 , 22 , 23 , 30 ]. Scanning electron microscopy (SEM) ( Figure 3 —right) revealed aggregated particles of variable size with no defined morphology [ 20 , 23 ].…”

Section: Resultsmentioning

confidence: 99%

“…Because of its versatility, this reaction is widely used. It involves the reaction of amines (e.g., 1,3,5-triazine-2,4,6-triamine (melamine), 1,4-bis-(2,4-diamino-1,3,5-triazine)-benzene,1,2,4,5-benzenetetramine, 2,3,6,7,10,11-hexaaminotriphenylene,2,3,6,7,14,15-hexaaminotriptycene, and 2,4,6-triaminopyrimidine) with aldehyde or ketone compounds (e.g., terephthalaldehyde, isophthalaldehyde, thieno[2,3-b]thiophene-2,5-dicarboxaldehyde, 1,3,5-benzenetricarboxaldehyde, and 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde) without expensive catalysts [ 8 , 16 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. The obtained porous network materials may be crystalline (crystalline covalent organic frameworks (COFs)) or amorphous (imine-linked polymer organic frameworks (i-POFs)).…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of an Imine-Linked Polymer Organic Framework for Storage and Release of H2S and NO

Carvalho

¹

,

Pires

²

,

Moiteiro

³

et al. 2023

Materials

4

0

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Hydrogen sulfide (H2S) and nitric oxide (NO) are especially known as toxic and polluting gases, yet they are also endogenously produced and play key roles in numerous biological processes. These two opposing aspects of the gases highlight the need for new types of materials to be developed in addition to the most common materials such as activated carbons and zeolites. Herein, a new imine-linked polymer organic framework was obtained using the inexpensive and easy-to-access reagents isophthalaldehyde and 2,4,6-triaminopyrimidine in good yield (64%) through the simple and catalyst-free Schiff-base reaction. The polymeric material has microporosity, an ABET surface area of 51 m2/g, and temperature stability up to 300 °C. The obtained 2,4,6-triaminopyrimidine imine-linked polymer organic material has a higher capacity to adsorb NO (1.6 mmol/g) than H2S (0.97 mmol/g). Release studies in aqueous solution showed that H2S has a faster release (3 h) from the material than NO, for which a steady release was observed for at least 5 h. This result is the first evaluation of the possibility of an imine-linked polymer organic framework being used in the therapeutic release of NO or H2S.

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“…6H2O at temperatures between 800 to 1000°C. TAP has been used previously as C-dopant in polymeric semiconductors and covalent organic materials to improve electronic conductivity and photocatalytic performance, [36,37] however its use as building block for conductive carbon-based electrocatalysts remains in its infancy, [38] and its polymerization pathway has not been elucidated up to date. In this work we selected TAP due to its structural similarities to melamine (Figure S1); melamine serves as precursor to the polymeric semiconductor graphitic carbon nitride (Figure S2), [39] which has been widely explored as a platform for single and dual atom catalysts.…”

Section: Resultsmentioning

confidence: 99%

FeNC Oxygen Reduction Electrocatalyst with High Utilisation Penta-coordinated sites

Barrio

¹

,

Pedersen

²

,

Sarma

³

et al. 2022

Preprint

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Atomic Fe in N-doped carbon (FeNC) electrocatalysts for oxygen (O2) reduction at the cathode of proton exchange membrane fuel cells (PEMFCs) are the most promising alternative to platinum-group-metal catalysts. Despite recent progress on atomic FeNC O2 reduction, their controlled synthesis and stability for practical applications remains challenging. A two-step synthesis approach has recently led to significant advances in terms of Fe-loading and mass activity; however, the Fe utilisation remains low owing to the difficulty of building scaffolds with sufficient porosity that electrochemically exposes the active sites. Herein, we addressed this issue by coordinating Fe in a highly porous nitrogen doped carbon support (~3295 m2 g-1), prepared by pyrolysis of inexpensive 2,4,6-triaminopyrimidine and a Mg2+ salt active site template and porogen. Upon Fe coordination, a high electrochemical active site density of 2.54×10^19 sites gFeNC-1 and a record 52% FeNx electrochemical utilisation based on in situ nitrite stripping was achieved. The Fe single atoms are characterised pre- and post-electrochemical accelerated stress testing by aberration-corrected high-angle annular dark field scanning transmission electron microscopy, showing no Fe clustering. Moreover, ex situ X-ray absorption spectroscopy and low-temperature Mössbauer spectroscopy suggest the presence of penta-coordinated Fe sites, which were further studied by density functional theory calculations.

show abstract

FeNC Oxygen Reduction Electrocatalyst with High Utilization Penta‐Coordinated Sites

Barrio

¹

,

Pedersen

²

,

Sarma

³

et al. 2023

View full text Add to dashboard Cite

Atomic Fe in N-doped carbon (FeNC) electrocatalysts for oxygen (O 2 ) reduction at the cathode of proton exchange membrane fuel cells (PEMFCs) are the most promising alternative to platinum-group-metal catalysts. Despite recent progress on atomic FeNC O 2 reduction, their controlled synthesis and stability for practical applications remains challenging. A two-step synthesis approach has recently led to significant advances in terms of Fe-loading and mass activity; however, the Fe utilisation remains low owing to the difficulty of building scaffolds with sufficient porosity that electrochemically exposes the active sites. Herein, we addressed this issue by coordinating Fe in a highly porous nitrogen doped carbon support (~3295 m 2 g -1 ), prepared by pyrolysis of inexpensive 2,4,6triaminopyrimidine and a Mg 2+ salt active site template and porogen. Upon Fe coordination, a high electrochemical active site density of 2.54×10 19 sites g FeNC -1 and a record 52% FeN x electrochemical utilisation based on in situ nitrite stripping was achieved. The Fe single atoms are characterised pre-and post-electrochemical accelerated stress testing by aberration-corrected high-angle annular dark field scanning transmission electron microscopy, showing no Fe clustering. Moreover, ex situ X-ray absorption spectroscopy and low-temperature Mössbauer spectroscopy suggest the presence of penta-coordinated Fe sites, which were further studied by density functional theory calculations. catalysts [7,8] or introducing axial ligands. Different FeN x active site axial ligands have been recently proposed following in situ Mössbauer, x-ray absorption spectroscopy, nuclear inelastic scattering or electron paramagnetic resonance. [9,10] Some of them bearing close resemblance to biological systems, [11] such as N axially coordinated FeN 4 sites resembling heme. [12] However, spectroscopic discernibility is often challenging in these typically heterogeneous FeNC catalysts, [13] therefore experimental structure-activity correlations are hard to conclude. To overcome experimental limitations, the effect of O axial ligands on model FeNC systems has been calculated by density functional theory, [14,15] although the effect of other possible axial ligands on different Fe sites (pyridinic and pyrrolic) has not been fully considered. [16] Alternatively, to improve catalyst performance, the number of active sites can be increased, an approach which has shown significant progress in recent years. [17] To selectively form a high density of atomic Fe sites and avoid undesired Fe-induced carbothermal reduction, Fellinger and coworkers first identified that the high temperature pyrolytic step (800-1000ºC) should be decoupled from the Fe loading, by using a suitable N x site template. [17][18][19][20] The decoupled two-step synthetic approach to prepare FeNC O 2 reduction catalysts has led to remarkable progress; Mehmood et al. recently showed bulk FeN x site density (SD Mössbauer, , Eq. 1-2) up to 7.4×10 20 sites g FeNC -1 . The reported in situ nitrite strippin...

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Triaminopyrimidine Based Porous Organic Polymers: Synthesis, Characterization and Catalytic Applications in One‐pot Room Temperature Synthesis of Dihydropyranopyranes

Cited by 11 publications

References 76 publications

Evaluation of an Imine-Linked Polymer Organic Framework for Storage and Release of H2S and NO

Evaluation of an Imine-Linked Polymer Organic Framework for Storage and Release of H2S and NO

FeNC Oxygen Reduction Electrocatalyst with High Utilisation Penta-coordinated sites

FeNC Oxygen Reduction Electrocatalyst with High Utilization Penta‐Coordinated Sites

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