Synthesis of novel nanoporous metal-organic gels with tunable porosity and sensing of aromatic compounds

Herein we report the bottom up design of novel porous metal-organic gels (MOGs) Fe-ndc (H₂ndc – 2,6-naphthalene dicarboxylic acid) and Fe-btc (H₄btc - 1,2,4,5-benzenetetracarboxylic acid) based on Fe³⁺. The effective strategy to obtain MOGs with controllable porosity by changing the concentrations of precursors was studied. The MOGs were dried in vacuum and the resultant xerogels were fully characterized using PXRD, TGA, FT-IR spectroscopy and SEM techniques. The resultant materials demonstrated a wide range of BET surface area 0–290 m²/g. Presence of micro (<2 nm), meso (2–50 nm) and macropores (>50 nm) in obtained xerogels was found. Furthermore, Fe-ndc demonstrated strong dependence of photoluminescence properties on the nature of the guest molecules. A unique enhancement effect of maximum luminescence intensity of the host framework Fe-ndc in the presence of toluene (862%). Introduction of benzene led to just 42% increase of luminescence intensity of material compared to Fe-ndc. Quenching effects of maximum luminescence intensity of the host framework upon introduction of nitrobenzene (67%) and 1,3-dinitrobenzene (46%) were found. These features make Fe-ndc an efficient fluorescent material for selective detection of hazardous highly energetic aromatic compounds.