Selectively Confined Poly(3,4-Ethylenedioxythiophene) in the Nanopores of a Metal–Organic Framework for Electrochemical Nitrite Detection with Reduced Limit of Detection

Abstract

Poly­(3,4-ethylenedioxythiophene) (PEDOT) selectively generated in the nanopores of a zirconium-based porphyrinic metal–organic framework (MOF), NU-902, is synthesized by in situ polymerization with the coexistence of MOF crystals and excessive poly­(sodium 4-styrenesulfonate) (PSS) followed by the successive washing steps to remove the well-dispersed PEDOT:PSS from the MOF-based solid. For comparison, PEDOT-NU-902 composite with PEDOT solely present between MOF crystals and that containing both pore-confined PEDOT and interparticle PEDOT are also synthesized by physical blending method and the in situ polymerization without adding PSS, respectively. Crystallinity, morphology, porosity, and electrochemical behavior of these PEDOT-NU-902 composites are investigated. Since both PEDOT and the porphyrinic linkers of NU-902 are active electrocatalysts for nitrite oxidation, these composites along with the pristine NU-902 and PEDOT are applied for electrochemical nitrite sensors in aqueous electrolytes. The composite with PEDOT solely confined within the MOF pores can effectively reduce the nonfaradaic current originating from PEDOT while achieving a moderate catalytic faradaic current for nitrite, which results in its smallest limit of detection (LOD) for nitrite determination compared to other PEDOT-NU-902 composites and the pristine materials. The electrochemical nitrite sensor based on pore-confined PEDOT achieves a sensitivity of 133 μA/mM cm2, a linear range of up to 1.6 mM, and a LOD of 1.71 μM. By utilizing nitrite detection as a proof-of-concept demonstration here, the findings suggest the unique role of the pore-confined conducting polymers within structurally rigid MOFs in electrochemical sensors and shed the light on the design and applications of such nanocomposites for a range of electroanalytical purposes.

Carbonized Nickel-Incorporated Metal–Organic Frameworks for Methane Reforming: Post-Synthetic Modification vs Impregnation

“…Metal–organic frameworks (MOFs), a relatively new category of nanoporous materials, , have been widely utilized as heterogeneous catalysts for a range of reactions owing to their highly porous characteristics and interconnected pore structures. − However, because of the poor thermal stability of MOFs, , the direct use of crystalline and stable MOFs in methane reforming is usually not feasible due to the high operating temperatures. MOF-derived materials, which are typically composed of porous metal oxides and/or nanocarbons synthesized by pyrolyzing MOFs, − are thus more common to act as the catalysts for methane reforming. − On the other hand, cerium­(IV)-based MOFs (Ce-MOFs) belong to an emerging subclass of MOFs with a relatively high porosity and stability. , As mentioned previously that ceria and nickel are attractive support and catalytic materials for BRM, respectively, we thus reasoned that by incorporating nickel in a Ce-MOF followed by carbonization, the resulting MOF-derived nickel supported by the porous ceria and carbon should be an appealing material for BRM.…”

Sulfonate-Functionalized Two-Dimensional Metal–Organic Framework as a “Dispersant” for Polyaniline to Boost Its Electrochemical Capacitive Performance

“…ICP-OES experiments were conducted to quantify the polymer-to-MOF ratios in all composites according to the method reported previously; , also see the Experimental Section for details. The results are shown in Table S1.…”

“…1 H nuclear magnetic resonance (NMR) measurements were performed on a Bruker Avance 600 NMR, and the experimental details can be found in our previous work. , ICP-OES data were gained by using a JY 2000–2 instrument (Horiba Scientific). For ICP-OES quantification, 5.0 mg of the MOF or MOF–PANI composite was accurately weighted and digested according to the procedure reported in our previous work. , After digestion, the resulting clear solution was diluted by adding 3 wt % of HNO 3 (aq) to 40 mL prior to ICP-OES measurements. Inductively coupled plasma-mass spectrometer (ICP-MS, Thermo-Element XR) was used to quantify the sulfur-to-zirconium ratios present in the materials.…”

“…For ICP-OES quantification, 5.0 mg of the MOF or MOF−PANI composite was accurately weighted and digested according to the procedure reported in our previous work. 40,60 After digestion, the resulting clear solution was diluted by adding 3 wt % of HNO 3 (aq) to 40 mL prior to ICP-OES measurements. Inductively coupled plasma-mass spectrometer (ICP-MS, Thermo-Element XR) was used to quantify the sulfur-tozirconium ratios present in the materials.…”

Zirconium Phosphate-Incorporated Polyaniline–Graphene Oxide Composite Modified Electrodes for Effective and Selective Detection of Nitrite

“…When appropriately adorned with a suitable material, it has the capacity to expedite the electrode process considerably, markedly lowering the overpotential observed on the bare electrode . The literature review on electrochemical sensors for the nitrite assay reveals the use of several functional nanomaterials such as carbon-based nanomaterials, , metal nanoparticles, , metal–organic frameworks (MOFs), , polymers, − and nanocomposites. , Nanoparticles have been used for electrode modification in electrochemical analysis because of the qualities such their enhanced active surface area, electrocatalytic action, and mass transfer . With these advantages, compared to the majority of electrodes, a greater analytical performance can be achieved by nanomaterial-modified electrodes.…”