Synthesis of Yolk/Shell heterostructures MOF@MOF as biomimetic sensing platform for catechol detection

Metal-organic frameworks (MOFs) have potential as heterogeneous biomimetic catalysts due to their high surface area, tunable porosity, and diversity of metals and functional groups. However, the activity and substrate specificity of pure monomeric MOFs still must be improved. Here, a size-selective MOF coating on the external surface of a biomimetic MOF is used to overcome these limitations of pure monomeric MOFs. The synthesis process of the biomimetic material involved first the coating of porous coordination network (PCN-222) cores with polyvinylpyrrolidone (PVP) as a structure-directing agent and then the modification of zeolitic imidazolate frameworks (ZIF-8). The yolk/shell PCN-222@ZIF-8-based sensor showed high selectivity for catechol but not for dopamine or L-DOPA. The PCN-222@ZIF-8 hybrid material-based sensor displayed 10 times more sensitivity than the PCN-222-based sensor, with low limit of detection (LOD) at 33 nmol L-1. Thus, ZIF-8 is a shell which allows the diffusion of specific substrate to the active sites of the PCN-222 and enriches the substrate. Furthermore, the PCN-222@ZIF-8 exhibits solvent adaptability, which overcomes the drawback of the natural HRP enzyme. This work opens a new avenue for construction of MOF@MOF biomimetic sensors and other applications.