2 research outputs found
Non-Noble-Metal-Based Porphyrin Covalent Organic Polymers as Additive-/Annealing-Free Electrocatalysts for Water Splitting and Biomass Oxidation
Though
metalloporphyrins have proved their efficiency as a class
of efficient electrocatalysts, their practical use is often restricted
due to poor stability and lack of an effective electrochemical surface.
Combining metalloporphyrins in the skeleton of covalent organic polymers,
though, is an effective strategy for developing efficient electrocatalysts
for OER and HER; due to the restricted conductivity of such materials,
addition of external additives or annealing is a must, which increases
the cost of the material development. Here, we report two metalloporphyrin-based
covalent organic polymers, COP-POR-Ni and COP-POR-Co, which work as
excellent annealing- and additive-free electrocatalysts for overall
water splitting in an alkaline medium. The polymers achieved a current
density of 1 mA/cm2 at 300 and 370 mV with turnover frequencies
(TOFs) of 9.1 × 10–3 and 2.68 × 10–3 s–1 at 2 mA/cm2 for
COP-POR-Ni and COP-POR-Co, respectively, for alkaline water oxidation.
The catalysts are also active for the selective conversion of 5-hydroxymethylfurfural
(HMF), a plant biomass carbohydrate, oxidation to a platform chemical
2,5-furandicarboxylic acid (FDCA) with the coproduction of hydrogen
at the cathode. HER activity was also achieved with overpotentials
of 468 and 348 mV at a current density of 1 mA cm–2 for COP-POR-Ni and COP-POR-Co in an acidic medium, respectively
A Siderophore Mimicking Gelation Component for Capturing and Self-Separation of Fe(III) from an Aqueous Solution of Mixture of Metal Ions
The carbohydrazide-based gelation component N2,N4,N6-(1,3,5-triazine-2,4,6-triyl)tris(benzene-1,3,5-tricarbohydrazide)
(CBTC) was synthesized and characterized using various
spectroscopic tools. CBTC and trimesic acid (TMA) get self-assembled to form metallogel with Fe3+, specifically through various noncovalent interactions in
a DMSO and H2O mixture. The self-assembly shows remarkable
specificity toward Fe(III) among different transition metal salts.
It is pertinent to point out that the binding specificity for Fe3+ can also be found in nature in the form of
siderophores, as they are mainly involved in scavenging iron selectively
from the surroundings. DFT studies have been used to investigate the
possible interaction between the different components of the iron
metallogel. To determine the selectivity of CBTC for
iron, CBTC, along with trimesic acid, is used to interact
with other metal ions, including Fe(III) ions, in a single system.
The gelation components CBTC and TMA selectively
bind with iron(III), which leads to the formation of metallogel and
gets separated as a discrete layer, leaving the other metal ions in
the solution. Therefore, CBTC and TMA together
show iron-scavenging properties. This selective scavenging property
is explored through FE-SEM, XPS, PXRD, IR, and ICP-AES analysis. The
FE-SEM analysis shows a flower-petal-like morphology for the Fe(III)
metallogel. The resemblance in the CBTC-TMA-Fe metallogel
and metallogel obtained from the mixture of different metal salts
is established through FE-SEM images and XPS analysis. The release
of iron from the metallogel is achieved with the help of ascorbic
acid, which converts Fe3+ to Fe2+. In biological
systems, iron also gets released similarly from siderophores. This
is the first report where the synthesized gelation component CBTC molecule is capable of scavenging out iron in the form
of metallogel and self-separating from the aqueous mixture in the
presence of various other metal ions