Dual-Functional Metal–Organic Framework for Luminescent Detection of Carcinoid Biomarkers and High Proton Conduction

Abstract

It remains a challenge to exploit dual-functional metal–organic frameworks (MOFs) for applications, including luminescence detection and proton conduction. With the deliberate selection of the bifunctional organic ligand 5-sulfoisophthalic acid monosodium salt (NaH2bts), and the phosphonic acid ligand N,N′-piperazine (bismethylenephosphonic acid; H4L), a robust three-dimensional (3D) noninterpenetrating dual-functional MOF, [Tb­(H2L)­(H2bts)­(H2O)]·H2O (1), has been synthesized hydrothermally. On the basis of the excellent thermal and chemical as well as superior luminescence stabilities in water and solutions with different pHs, 1 can serve as the simple, rapid, and highly selective and sensitive luminescence detection of the carcinoid biomarkers 5-hydroxytryptamine (HT) and its metabolite 5-hydroxyindole-3-acetic acid (HIAA) with detection limits of nanomolar magnitude in water and in simulated blood plasma and urine systems. Due to the change in the signals that could be readily differentiated by the naked eye under a UV lamp, a portable test paper has been developed. The probable quenching mechanisms are discussed in detail. In addition, a great number of hydrogen-bonding networks are formed among the uncoordinated carboxylic oxygen atoms, sulfonate oxygen atoms, protonated nitrogen atoms, and water molecules, which provide potential proton-hopping sites for proton conduction, leading to a maximum proton conductivity of 2.3 × 10–4 S cm–1 at 368 K and 95% relative humidity. The above results suggest that rationally designed dual-functional MOFs can open an avenue for the development of occupational diagnostic tools and alternative energy technology.

Water-Mediated Proton Conduction in Metal–Organic Frameworks with High Water Stability Constructed by a Terpyridine Tricarboxylate Ligand

“…For instance, the σ values of H 3 tcpb-H 2 O increased from 8.41 × 10 –5 to 1.90 × 10 –3 S·cm –1 with increasing RH (68–98% RH) at the fixed 100 °C. It is not difficult to find that the σ value of H 3 tcpb-H 2 O enhanced from the lower RH to the higher RH at a given temperature by 2 to 3 orders of magnitude, which is quite normal and reasonable for the proton conductor. , …”

Two Stable Cd-MOFs as Dual-Functional Materials with Luminescent Sensing of Antibiotics and Proton Conduction

“…74,75 To further verify the IFE mechanism, ultraviolet absorption titrations were performed. 28,66 As shown in Figure S15, as the amount of CAP gradually increased, the absorption intensities of 1 and 2 were obviously enhanced. The more excitation light could be absorbed with the increase of CAP concentration, resulting in luminescent quenching.…”

“…Second, it can be found there is an obvious overlap between the excitation spectra of 1 and 2 and the absorption spectrum of CAP (Figure ), demonstrating the presence of IFE. , To further verify the IFE mechanism, ultraviolet absorption titrations were performed. , As shown in Figure S15, as the amount of CAP gradually increased, the absorption intensities of 1 and 2 were obviously enhanced. The more excitation light could be absorbed with the increase of CAP concentration, resulting in luminescent quenching.…”

High‐Performance All‐Solid‐State Proton Rectifier Using a Heterogeneous Membrane Composed of Coordination Polymer and Layered Double Hydroxide

“…This must be a reflection of the concentration of water in the pores, which can serve as hopping sites for protons originating from the uncoordinated carboxylic groups (Figure S1). [22] The Mg-Al-LDH-(NO 3 ) membrane also showed humidity-dependent proton conductivity (Figure 3f); however, the conductivity change is less pronounced than that of the Cu 2 (CuTCPP) membrane. The presence of hydroxyl groups at higher concentrations than the proton species in Cu 2 (CuTCPP) appears to be a part of the reason for humidity-independent conduction.…”