The Use of Lanthanide-MOFs for the Detection of VOCs Derived from Tire Burning and Crude Oil Emissions

Graduate #49
Discipline: Chemistry and Chemical Sciences
Subcategory: Pollution/Toxic Substances/Waste

Carlos L. Crawford Jr. - North Carolina A&T State University

Volatile organic compounds emitted from the tire burning and crude oil emissions have impacted many areas across the United States. These pose serious mutagenic and carcinogenic concerns to communities which spur the need for sensors designed to detect the various compounds emitted from these anthropogenic sources. We hypothesize that lanthanide metal organic frameworks (LnMOFs) could be used to detect these various VOCs through the manipulation of physical properties and affinities between lanthanides and N,O-heterocycles to effectively sensitize lanthanide luminescence by overcoming their forbidden f-f transitions.

LnMOFs containing europium, terbium and organic ligands bathophenanthroline, dibenzothiophene, and 4-amino-2-(1-piperidinyl)pyrimidine-5-carbonitirle (4APPC), were synthesized to access their viability as sensors. These complexes were synthesized through the use of green chemistry techniques, mechanochemical, and hydrothermal methods and studied through Gaussian 09 computational chemistry modeling software. The Eu-bathophenanthroline and TbAu(CN)2DBT complexes show sensitized luminescence of the europium 5D0 <> 7F1,2 peaks, while alteration of the dibenzothiophene emission has been observed in the later system. These results were further characterized by FT-IR, UV-Vis Spectroscopy, and X-ray Diffraction. The Tb-4APPC complex shows ineffective terbium sensitization with energy being back transferred to enhance the 4APPC emission at 510nm. The 4APPC ligand showed interesting solid state luminescence switching going from a green emission (518nm, 576nm) in its powder form to a blue emission (443nm, 480nm) in its crystalline form. These differences are due to the difference in packing with green emission arising from π-π stacking interactions and the blue emission from H-bonding interactions. This difference in solid state luminescence contributes to new switchable luminescent devices. Future research will expound on selectivity of these sensors along with the various avenues that solid state luminescence switching has available for our framework sensor devices.

Not Submitted

Funder Acknowledgement(s): This research was funded through the Title III program grant.

Faculty Advisor: Zerihun Assefa, zassefa@ncat.edu