Spin-crossover metal-organic frameworks: promising materials for designing gas sensors

We present a quantitative study of the sensing behavior of micro-patterned gratings based on the metal-organic framework type spin crossover complex Fe(bpac)[Pt(CN)(4)] (1) in the presence of vapors of various organic compounds. The gratings of 1 were fabricated by combining a sequential assembly technique and a photolithographic method. The guest absorption driven change of the spin state and the associated variation of the refractive index were in situ monitored by optical diffraction on a grating of 1. Our sensor is characterized by good reversibility, room temperature operation, a low limit of detection (similar to 30 ppm for molecules of iodobenzene) as well as a linear dynamic range of detection (from 300 to 1500 ppm). The possibility of selectively desorbing the analytes by thermal annealing confers also selectivity to the sensor.