Low-cost inkjet printing of metal-organic frameworks patterns on different substrates and their applications in ammonia sensing

Due to their vivid material properties, metal-organic frameworks (MOFs) have been successfully proven useful in a wide variety of applications. In recent years, MOFs have been explored in electrical, electronic, and optical devices as well. The fabrication of such devices requires a controlled growth of thin films of MOFs on diverse substrates. In the present work, we demonstrate a simple way of inkjet printing for the patterning of thin films of transition metals and Terbium (Tb) MOFs on substrates like paper and flexible PET (polyethylene terephthalate). In particular, inkjet printing of Cr-MIL-101, Mn-BDC, Fe-MIL-101, Co-MOF-71, and Ni-BDC MOFs is one of the novel aspects of this work. The printed patterns have been characterized with different instrumental techniques. The studies have confirmed that the inkjet printing technique can conveniently facilitate the growth of homogeneous MOF thin film patterns with intact structural and functional characteristics. The experiments have also proven that the basic characteristics of the patterned MOFs remains stable for months. Two printed patterns, i.e., one Mn- and one Tb- based MOF films, have been demonstrated as colorimetric/fluorescent sensing strips for easy detection of ammonia vapor with reasonable sensitivity. The films have facilitated the detection of ammonia over 5-80 ppm with a low limit of detection of 0.3 ppm.