Fabrication and Surface Modification of Niobium Metal–Organic Framework Membrane and its Gas Sensing Application

Abstract The niobium metal–organic framework (Nb‐MOF = [Nb 2 (bdc) 2 (NDI)] n ) membrane, constructed from terephthalic acid(bdc) and 1,8,4,5‐naphthalenetetracarboxdiimide (NDI), is in this work grown on the surface of lithium niobate (LiNbO 3 ) film composite optical waveguide (COWG) substrate using UV‐light illumination method. After growing for 20 min, the Nb‐MOF membrane forms as a graphene‐like structure with 50 nm pore size and 96 nm thickness. At room temperature (25 °C), in terms of COWG sensors, Nb‐MOF exhibits the greatest response to H 2 S and SO 2 , followed by ethylenediamine (EDA) and NO 2 , coexistence with 15 kinds of benzenes, amines, and acidic gases. In order to improve its response selectivity, the spirooxazine (SP) is embedded into the Nb‐MOF frame, and a SP@Nb‐MOF membrane COWG with smooth‐snowflake imprinted surface is obtained. In gas sensing performance, the obtained COWG shows the greatest response to H 2 S, while the response of SO 2 , NO 2 , and other gases are obviously diminished. When the SP@Nb‐MOF membrane exposes to H 2 S gas, proton‐transfer and morphology modulation are induced. The presented sensor also shows a wide detection range (1 × 10 4 –0.1 ppb), fast response (4 s), and long‐term stability of 120 d to H 2 S at room temperature (25 °C) and 25% relative humidity.