Pyrene Bearing Azo-Functionalized Porous Nanofibers for CO₂ Separation and Toxic Metal Cation Sensing

Abstract

A novel luminescent azo-linked polymer (ALP) has been constructed from 1,3,6,8-tetra(4-aminophenyl)pyrene using a copper(I)-catalyzed oxidative homocoupling reaction. The polymer displays high porosity with a Brunauer–Emmett–Teller surface area of 1259 m 2 g –1 and narrow pore size distribution (1.06 nm) and is able to take up a significant amount of CO 2 (2.89 mmol g –1 ) at 298 K and 1.00 bar with a high isosteric heat of adsorption of 27.5 kJ mol –1 . Selectivity studies applying the ideal adsorbed solution theory revealed that the novel polymer has moderately good selectivities for CO 2 /N 2 (55.1) and CO 2 /CH 4 (10.9). Furthermore, the ALP shows fluorescence quenching in the presence of Hg 2+ , Pb 2+ , Tl + , and Al 3+ ions. Compared with these ions, the ALP showed no sensitivity to light metal ions such as Na + , K + , and Ca 2+ in ethanol–water solution, clearly indicating the high selectivity of the ALP toward heavy metal ions. The exceptional physiochemical stability, high porosity, and strong luminescence make this polymer an excellent candidate as a fluorescent chemical sensor for the detection of heavy metal ions.

Covalent Organic Polymers and Frameworks for Fluorescence-Based Sensors

“…For instance, an azo-linked conjugated COP exhibited fluorescence quenching when exposed to heavy metals but showed no response to light metals such as Na + and Ca 2+ . This difference was rationalized by the hard acid nature of Na + , K + , and Ca 2+ , which leads to a low affinity for aromatic systems and azo groups …”

“…Groups of Metal Cations with Common Physical Properties. Some sensors for heavy metal cations were not specific to a particular metal such as the ones presented above but rather exhibited selectivity based on common properties of metal ions, such as valency and/or oxidation number, 43,45 atomic mass, 46 and/or metals with filled d-orbitals. 47 The utility of these systems depends on their purpose; they might be very helpful when the presence of any kind of heavy metal is of interest but less so when our interest is in a particular metal ion.…”

Redox-Active Porous Organic Polymers as Novel Electrode Materials for Green Rechargeable Sodium-Ion Batteries

“…Herein, we report the first use of highly porous azo-linked polymers (ALPs) − as a new redox active electrode material for SIBs. ALPs are highly cross-linked polymers and thus would eliminate the solubility issue, which is prominent in small organic molecules and leads to fast capacity fading.…”

Organically Functionalized Mesoporous SBA-15 Type Material Bearing Fluorescent Sites for Selective Detection of HgII from Aqueous Medium

“…The mesoporous and calcined SBA-15 was synthesized as per the reported method. 26 Chloro-functionalized SBA-15 was prepared in stirring and refluxing conditions for 24 h where 0.20 g of as-synthesized SBA-15 was taken in 10 mL of dry toluene and 0.6 mmol (0.144 g) of ClPTES was added to it dropwise under a N 2 atmosphere. A white solid was obtained after cooling the suspension at room temperature.…”

“…Porous nanomaterials with pore dimensions varying from sub-nanometer (microporous) to several nanometer (mesoporous) length scales are intensively studied over the years due to their potential in several frontline application areas and their reusability. − These solids are quite stable in water, which could make them ideal candidates for ground water purification. Among them, the mesoporous SBA-15 − material is often employed as a support to enhance the material properties due to its structural features such as high surface area with a thick pore wall, uniformly ordered pore channels, high thermal stability, optical transparency in the visible region, and high biocompatibility .…”