Flexible luminescent non-lanthanide metal-organic frameworks as small molecules sensors

Toxic, carcinogenic, and hazardous materials are omnipresent, generally obtained by anthropogenic activities, industrial activities, aerobic and anaerobic degradation of waste materials and are harmful to human health and environment. Thus, sensing, colorimetric detection, and subsequent inclusion of these chemicals are of prime importance for human health and environment. In comparison to other classes of highly porous materials, luminescent metal-organic frameworks (LMOFs) have chromophoric organic ligands, high surface area, high degree of tunability and structural diversity. They have received scientific interest as sensory materials for device fabrication to detect and sense toxic small molecules. Especially, as soft-porous materials exhibiting a degree of flexibility or dynamic behaviour, flexible LMOFs are promising for selective detection and sensing, and for encapsulation of toxic and health hazardous molecules. Such flexible LMOFs offer a potential platform for selective adsorption/separation, molecular recognition, and sensing application. In this perspective, we highlight the advantages of flexibility of LMOFs for selective detection and sensing, and inclusion of toxic small molecules (solvents, anions, halobenzenes, aromatics, aromatic amines, nitro-explosives and acetylacetone). In addition, the principles and strategies guiding the design of these MOF based materials and recent progress in the luminescent detection of toxic small molecules are also discussed. In this perspective we limit our discussion on the 'non-lanthanide' based luminescent MOFs that have flexibility in the framework and show small molecule sensing applications.