Owing to superior sorption properties, structural variability, and versatility, metal-organic frameworks (MOFs) are used as sensing materials with both high selectivity and sensitivity. Herein, integrating a MOF with a polymer, a multilayered photonic crystal (PC) sensor, which is composed of NH2-MIL-88B nanocrystals and poly(styrene-acrylic acid) nanoparticles, is fabricated. Synthetically, by taking advantage of the sensitive breathing effect of the MOF and excellent stimuli-response of the copolymer, the sensor outputs significant optical signals that can be visually recognized and captured with the assistance of the spectrum with the detection limits of 3.70, 0.87, 0.42, and 0.22 g/m3 when exposed to benzene, toluene, ethylbenzene, and xylene (BTEX), respectively. Thanks to the porous construction and ultrathin feature, the PC sensor reaches a sensing balance within 3 s in BTEX streams and restores its initial state immediately after the rapid volatilization of the vapors. The function of the MOF material is confirmed by comparing the sensing properties of MOF/polymer PC with those of the SiO2/polymer one. In addition, as the designed MOF/polymer-based PC sensor shows different spectrum characteristics compared with those of other reported MOF-based ones, finite element simulation technology is adopted to help explain the relationship between optical property and material structure feature of the multilayered PC structure.
Keywords: colorimetric sensing; flexible MOFs; functional polymer; optical properties; photonic crystals.