جنبه های الکتروشیمیایی مدرن برای سنتز محصولات ارگانیک ارزش افزوده The Applications of Metal-Organic Frameworks in Electrochemical Sensors

1. Introduction The research on the synthesis and applications of metal-organic frameworks (MOFs), which are also known as porous coordination polymers, has been growing tremendously over the past few decades. MOFs exist as extended crystalline lattices comprising coupling units (metal centers or clusters) coordinated by electron-donating organic ligands. MOFs have the large internal pore volumes (up to 90% free volume) with well defined pore sizes and highest specific surface areas (beyond a Langmuir surface area of 10 000 m2 g -1 ) among the reported porous materials, which play a crucial role in functional applications, typically in gas storage and separation, drug delivery, and sensing.[1,2] Furthermore, their pore sizes of the microporous characters could be tuned from several angstroms to several nanometers based on the length control of the rigid organic linkers. Plenty of metal ions, organic linkers and structural motifs provide an essentially infinite number of possible combinations.[3,4] Thus, their structures could be designed for the different target molecules by the selection of the coordination nodes and organic linkers. Importantly, versatile framework functionalities beyond the accessible porosity could be produced from the metal centers (eg. electricity, catalysis, magnetism), organic ligands (eg. luminescence, fluorescence, chirality) or a combination of both.[5–8] Electrochemical sensors are widely applied for a range of applications including environmental monitoring, food quality control, medical diagnostics, and chemical treat detection. The sensitivity and selectivity are important elements to consider in optimizing the performance and utility of the electrochemical assay. The high porous and surface areas of MOFs could load the guest molecules and/or catalyze the targets with high catalytic activity, which affords inherent sensitivity for the electrochemical detection.[9] The porosity of MOF-based materials permits guest molecules to diffuse into the bulk structure, and the shape and size of the pores produce to shape- and size-selectivity over the incorporated guests.[9–11] Another source of selectivity is chemically specific interactions between the guest molecules and MOFs via hydrogen bonding, π-π interactions, open metal sites, and van der Waals interactions.