Highly Water‐Stable Lanthanide–Oxalate MOFs with Remarkable Proton Conductivity and Tunable Luminescence

Abstract

Although proton conductors derived from metal-organic frameworks (MOFs) are highly anticipated for various applications including solid-state electrolytes, H sensors, and ammonia synthesis, they are facing serious challenges such as poor water stability, fastidious working conditions, and low proton conductivity. Herein, we report two lanthanide-oxalate MOFs that are highly water stable, with so far the highest room-temperature proton conductivity (3.42 × 10 S cm ) under 100% relative humidity (RH) among lanthanide-based MOFs and, most importantly, luminescent. Moreover, the simultaneous response of both the proton conductivity and luminescence intensity to RH allows the linkage of proton conductivity with luminescence intensity. This way, the electric signal of proton conductivity variation versus RH will be readily translated to optical signal of luminescence intensity, which can be directly visualized by the naked eye. If proper lanthanide ions or even transition-metal ions are used, the working wavelengths of luminescence emissions can be further extended from visible to near infrared light for even wider-range applications.

Structure Engineering of a Lanthanide‐Based Metal–Organic Framework for the Regulation of Dynamic Ranges and Sensitivities for Pheochromocytoma Diagnosis

“…However, the literature has seen little exploration regarding the engineering of the MOF structure properties to regulate the dynamic ranges and sensitivities of MOF‐based probes, though they have been widely investigated and developed for detecting various analytes. [ 18–30 ] Moreover, only a few of these MOF‐based sensors are used for recognizing disease‐related markers, [ 23,24,28 ] and they are also limited to an unoptimizable detection range with insufficient responses to small changes of the targets concentration, which is unsatisfactory for precise diagnosis of disease. Herein, we report a novel strategy to engineer a luminescent lanthanide‐based metal–organic framework (Eu‐ZnMOF) biosensor with tunable detection performances for tracing the overexpressed VMA in urine ( Scheme ).…”

Metal–Organic Frameworks as a Versatile Platform for Proton Conductors

“…Oxalate‐based MOF is a typical class of proton conductors that have been extensively studied. [ 73–77 ] Among these, ferrous oxalate dihydrate [Fe(ox)·2H 2 O] [ 73 ] is worth mentioning, which was constructed by the Fe(II) ions, oxalate ions and coordinated water molecules. At 25 °C and 98% RH, Fe(ox)·2H 2 O exhibited a high proton conductivity, with the σ value of 1.3 × 10 −3 S cm −1 .…”

Understanding geology through crystal engineering: coordination complexes, coordination polymers and metal–organic frameworks as minerals

“…Not much is known about the physico-chemical properties of zhemchuzhnikovite, stepanovite or deveroite, but analogies with synthetic systems raise the very exciting prospect that such MOF minerals could exhibit highly sophisticated and functional properties, such as excellent proton conductivity, selective adsorption of different small molecules, possibly coupled with luminescence in the case of lanthanide-based MOFs (Zhang, Xie et al, 2017). For example, both the overall structure and the arrangement of hcb-layers in zhemchuzhnikovite are strikingly similar to those seen in analogous zincbased MOFs reported by the Kitagawa group (Sadakiyo et al, 2014).…”