Fabrication of Robust and Porous Lead Chloride-Based Metal–Organic Frameworks toward a Selective and Sensitive Smart NH₃ Sensor

Abstract

Organolead halide materials have shown promising optoelectronic properties that are suitable for light-emitting diodes (e.g., strong photoluminescence, narrow emission width, and high charge carrier mobility). However, the vast majority of them have no open porosity or open metal sites for host−guest interactions and are therefore not widely applicable in intrinsic fluorescent sensing of small molecules. Herein, we report a lead chloride-based metal−organic framework (MOF) with high porosity and stability and promising photoluminescent characteristics, performing as a sensitive, selective, and long-term stable fluorescence probe for NH 3 . For the first time, a homemade dynamic realtime photoluminescence monitoring system was developed, which showed that our haloplumbate-based MOF has an immediate response and an extremely low limit of detection (12 ppm) toward NH 3 . A variety of experimental characterization and theoretical calculations evidenced that the photoluminescence quenching was ascribed to the coordination between NH 3 guests and exposed Pb 2+ centers in MOFs. Moreover, a portable on-site smart NH 3 detector was designed based on this haloplumbate-MOF using a 3D printer, and the quantitative recovery experiment demonstrated the effective detection of NH 3 in the range of 15−150 ppm. This study opens a new pathway to design organolead halide-based MOFs to perform on-site chemical sensing of small molecules and shows their high potential to monitor safety concentrations of NH 3 in different industrial sites.

Organolead Halide-Based Coordination Polymers: Intrinsic Stability and Photophysical Applications

“…The chemical functionalization of MOFs is successful by isoreticular synthesis with 2-aminoterephthalic acid (NH 2 -bdc), which is a typical precursor for postsynthetic modification (Figure 2b). 38 The expansion of MOF porosity is realized by using longer linker containing two phenylene ring, biphenyl-4,4′-dicarboxylate. In this case, the 1D SBUs are symmetric, and present the chemical compositions of [Pb 3 X 2 ] 4+ (X = Cl − /Br − ).…”

“…Our group reports a 1D porous coordination polymer based on [Pb 3 Cl 2 ] 4+ chains as SBUs, exhibiting linear dependence between PL intensity and NH 3 concentration (0∼400 ppm) with a low detection limit of 12 ppm. 38 Owing to the confined porosity and the mechanism of Pb-NH 3 coordination, the material demonstrates high selective responses over competing interferents, e.g. organic amines and other gaseous molecules (N 2 , CO 2 and O 2 ).…”

“…Interestingly, unlike the well-defined symmetric metal-oxo SBUs in the benchmark MOFs, the lead halide-based SBUs are highly asymmetric and possess distorted square [Pb 2 X 2 ] 2+ (X = Cl – /Br – /I – ) units that are linked by μ 2 -X – into zigzag chains (Figure c). The chemical functionalization of MOFs is successful by isoreticular synthesis with 2-aminoterephthalic acid (NH 2 -bdc), which is a typical precursor for postsynthetic modification (Figure b) . The expansion of MOF porosity is realized by using longer linker containing two phenylene ring, biphenyl-4,4′-dicarboxylate.…”

Supramolecular FeII4L4 cage for fast ammonia sensing

“…For comparison, we summarized the sensing performance and detection technology of the MOC-1 sensor and other traditional NH 3 sensors such as the metal oxide conducting polymer, and MOFs, as listed in Table S8 (ESI †). This result indicated that MOC-1 exhibited high detection sensitivity towards NH 3(g) at r.t. and the smartphone-based analytical method was simple, convenient and time-saving without complicated detection technologies and sophisticated instrumentation such as fluorescence spectroscopy 29 and resistance measurement. 4 57 Fe Mo ¨ssbauer spectroscopy measurements on MOC-1 and MOC-1@NH 3 were run to assess the sensing mechanism and probe the spin and oxidation states of this material (Table 1).…”

Isoreticular Postsynthetic Modification of Robust Organocopper(I) Halide Hybrids for Enhanced Broad-Band Emission and Turn-On NH3 Sensing

“…It is more challenging to finely tune the structures and emissive properties of these solids at the molecular level while preserving the parent lattice structure. , Very few postsynthetic treatments (e.g., light or CH 2 Cl 2 ) have been reported to “turn-on” the self-trapped emission of organometal halide hybrids but involving a drastic structural change and not being air-stable to perform photoactive applications. , For photoluminescence sensing of NH 3 , the vast majority of the previously reported materials undergo the “turn-off” process without reusability or employ perovskite quantum dots that may decompose under ambient conditions. − Herein, we report two organometal halide crystalline materials with 1D deformable [Cu 2 X 2 ] (X = Cl or Br) chains, which are linked by 1 H -pyrazole-4-carboxylic acid (PyC). Both of the materials demonstrate enhanced self-trapped emission upon chemical treatment with 500 ppm NH 3 , exhibiting a substantial increase of the PLQY from 5–5.5 to 60–75%.…”