A dual-function Cd-MOF with high proton conduction and excellent fluorescence detection of pyridine

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 51; no. 17; pp. 6687 - 6695
• Main Authors: Wu, Guo-Mei, Zhang, Ming-Yue, Wang, Feng-Dong, Zhang, Chen-Xi, Wang, Qing-Lun
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 03.05.2022
• Subjects: Cadmium; Chitosan; Fluorescence; Fluorescent Dyes; Fluorescent indicators; Fuel cells; Hydrogen bonds; Metal-organic frameworks; Metal-Organic Frameworks - chemistry; Phosphonates; Proton conduction; Protons; Pyridines; Relative humidity; Water
• ISSN: 1477-9226; 1477-9234; 1477-9234
• DOI: 10.1039/d2dt00193d

Metal-organic frameworks have great potential in the field of proton conducting materials and fluorescent probes due to their structural tunability and designability. A novel water-stable metal organic framework material [Cd 2 (Hdpb)(H 2 O) 3 ] (Cd-MOF) was synthesized based on H 5 dpb (H 5 dpb = 3,5-diphosphonobenzoic acid) and Cd 2+ ions. Cd 2+ ions are connected with phosphonates and carboxyl groups of H 5 dpb to form an infinitely extended 1D chain, which is further connected by the Hdpb 4− ligand and coordinated water to form a three-dimensional network structure. There are hydrogen bond networks in the 3D structure of the Cd-MOF, which are favorable for proton transfer, achieving its maximum proton conductivity of 2.97 × 10 −3 S cm −1 at 338 K and 98% relative humidity (RH). To realize its application in fuel cells, the Cd-MOF was introduced into the chitosan (CS) matrix, and a series of composite membranes (Cd-MOF@CS- X ) with high proton conductivity were obtained. The results of AC impedance show that the proton conductivity of Cd-MOF@CS-5 reaches 3.55 × 10 −1 S cm −1 at 358 K and 98% RH, which is comparable to the highest values reported for MOF-polymer complexes. Moreover, the Cd-MOF can be used as a selective fluorescent probe for pyridine detection, and its detection limit can reach 1.0 × 10 −6 M. A bifunctional MOF with proton conduction and pyridine recognition is reported for the first time, and has important reference value for the practical application of functional MOFs in both electrochemical and luminescence sensing. A dual-functional Cd-MOF with high proton conductivity (2.97 × 10 −3 S cm −1 ) and selective recognition of pyridine (LOD = 1.0 × 10 −6 M) was obtained. Its composite membrane Cd-MOF@CS-5 has an ultra-high proton conductivity of 3.55 × 10 −1 S cm −1 .