Fabrication of an NH2-MIL-88B photonic film for naked-eye sensing of organic vapors

Metal-organic frameworks (MOFs) as thin films have gained considerable attention in recent years because of their potential applications in different fields. However, preparation of integrated photonic MOF films still remains a major challenge. This study reports an approach for the fabrication of NH2-MIL-88B photonic films with potential for general application to other MOF films based on the simple spin-coating technique. A systematic study on the effect of MOF suspension concentration, rotation speed, and rotation cycles on the thickness and optical quality of coated films is presented. Moreover, the sensing performance of the NH2-MIL-88B photonic film deposited on a silicon wafer is evaluated using ultraviolet-visible reflection analysis and an optical digital camera, revealing the selective response to various organic vapors. More importantly, such selective sensing behavior can be easily and rapidly visualized by the naked eye.