The Catalyst Review June 2024 - 15

Triazene-Linked Porous Organic Polymers for Heterogeneous Catalysis and Pollutant Adsorption
Porous organic polymers (POPs) are highly promising materials for heterogeneous catalysis and pollutant adsorption from aqueous medium due to their
high surface area, permanent porosity, monomer diversity, and synthetic versatility. In this work, two triazene-linked POPs were prepared under mild
reaction conditions and used as heterogeneous catalysts and adsorbents to remove dyes and heavy metals from aqueous solution.
The authors began by synthesizing two triazene-linked POPs via the N-coupling diazotization reaction between the bis-diazonium derivative of
1,3,5-tris(4-aminophenyl)triazine (TAPT) and benzidine (Bd) or 4,4'-diamino-[1,1'-biphenyl]-2,2'-disulfonic acid (Bd(SO3
and TAPT-Bd(SO3H)2-POP, respectively (Figure 1). Extensive characterization of these materials, including TAPT-Bd(SO3
H)2
g−1
Na)2
)-affording TAPT-Bd-POP
-POP, involved FTIR
spectroscopy, Raman spectroscopy, CP/MAS 13C NMR spectroscopy, and thermogravimetric analysis. The results of these studies indicated high BET
surface area, porosity, and thermal stability. TAPT-Bd-POP exhibited the highest BET surface area (133 ± 2 m2
(10.4 nm) among the materials studied.
Using these triazine POPs as catalysts
for the Henry, Knoevenagel, and
Biginelli reactions resulted in good-toexcellent
performance. For example,
when used in the Knoevenagel
condensation between ethyl
cyanoacetate and aromatic aldehydes
(Table 1), the results indicate that,
overall, TAPT-Bd-POP is a more
efficient catalyst compared to
TAPTBd (SO3
Na)2
-POP.
Triazene POPs were evaluated as
adsorbents for organic dyes and heavy
metals in an aqueous solution. Four
different organic pollutants were
chosen as models to evaluate the
adsorption performance in relation to
the adsorbates' charge and molecular
size. Two cationic adsorbates (at
the working pH of 5 and 5−6) of
different sizes were used-methylene
blue (MB, pKa 3.869,70) and crystal
violet (CV; pKa1
1.15 and pKa2
1.80).
Phenol red was used as the anionic
model (PhR, pKa 7.973), and phenol
as the neutrally charged pollutant
with the smallest dimensions (PhOH,
pKa 9.970). Copper (II) nitrate and
sodium dichromate solutions were
used for heavy-metal adsorption.
The adsorption performance of
triazene POPs was found to be very
satisfactory compared to other POP
adsorbents exhibiting maximum
adsorption capacities up to 953 ± 71
mg g−1
Na)2
-POP is
Figure 1. Syntheses and structures of TATP-Bd-POP and TAPT-Bd(SO3
applications in heterogeneous catalysis and pollutant removal.
H)2-POP and their respective
) and lowest BET average pore diameter
Table 1. Triazene POP-Catalyzed Knoevenagel Condensation Between Ethyl Cyanoacetate and Aromatic
Aldehydes
for the adsorption of methylene
blue. Preliminary results indicate
that TAPT-Bd-(SO3
significantly more efficient in removing
cationic pollutants, while TAPT-BdPOP
was more efficient in removing
anionic pollutants. Machado TF,
Artur JM, Serra, MES, et al. (2024). ACS Appl. Polym. Mater. https://doi.org/10.1021/acsapm.4c00225.
The Catalyst Review
June 2024
15
https://www.doi.org/10.1021/acsapm.4c00225
The Catalyst Review June 2024

Table of Contents for the Digital Edition of The Catalyst Review June 2024
