Inicio 9 Research topics 9 Lanthanide-based field-deployable metal-organic frameworks (MOF) for selective NO2 detectors

RESEARCH PROGRAMMES

P1: Organic nanosystems for Light harvesting and Energy Conversion

RESEARCH SUPERVISOR(S)

Dr Juan Cabanillas Gonzalez
Research Group website: https://juancabanillas.wixsite.com/research

Dr Jose Sanchez Costa
Research Group website: https://www.nanociencia.imdea.org/switchable-nanomaterials-group/group-publications

RESEARCH TOPIC DESCRIPTION

Among the hazardous gases released from fossil fuels combustion, nitrogen dioxide (NO2) and related nitrogen oxides, (NOx), are some of the most dangerous. Any NOx form can cause serious damage to the respiration system when breathed at levels beyond 1 ppm. The most common effects are lung tissues damage and aggravation of respiratory diseases or heart conditions. NOx also plays a role in the chemistry of the atmosphere, contributing to ozone formation, smog and acid rain. Air quality monitoring of NOx in urban areas is therefore necessary due to the daily massive production of these harmful gases. Presently, there is a wide range of NO2 sensors in the market, the most common being chemiresistors based on semiconducting metal oxides. [Chem. Mater. 1996, 8, 2298.] This technology, however, has some drawbacks. Sensitivity to NO2 on the ppm scale is achieved but requires heating the oxide layer over 200 ºC. [Sens. Actuators B, 2011, 157, 510.] Selectivity is poor and requires monitoring sensor arrays from different semiconducting oxides. [Small, 2006, 2, 36].

Recently, we demonstrated how two isostructural lanthanide-based metal-organic frameworks (Tb- and Eu-MOF) with 2-amino-1,4-benzene dicarboxylic acid (NH2-BDC) as organic linker undergo divergent photoluminescence (PL) quenching and enhancement respectively, upon NO2 binding (see Figure 1 for further details). This opposite behaviour was explained as due to NO2 specific binding to NH2 groups via H-bonding, leading to a strong charge transfer (CT) interaction. Outstandingly, the integration of both lanthanide centres in the same MOF is expected to lead to spectrally-dependent luminescence enhancement/quenching, a distinctive luminescence recognition pattern to detect NO2 via ratiometric luminescence measurements [J. Phys. Chem. Lett., 2020, 11, 3362]. Based on our findings, we propose the development of NO2-responsive Ln-MOFs capable to selectively reveal the presence of NO2 in low concentrations via a novel PL transduction mechanism.

POSITION DESCRIPTION

The candidate will perform synergetic research between two complementary research groups led by Dr Juan Cabanillas Gonzalez (Time-resolved optical spectroscopy) and Dr Jose Sanchez Costa (Switchable nanomaterials). The changes in the photophysical pathways of the MOFs induced by NO2-MOF interactions will be investigated with the techniques available at the Time-resolved optical spectroscopy laboratories (fs-Transient absorption spectroscopy and time-resolved photoluminescence). In the SNM group the candidate will synthesize MOFs with coordination chemistry methods. These activities will be complemented with X-ray single crystal diffraction and the study of the physical properties with NMR, HPLC, MALDI-MS, optical spectroscopy (IR, UV-vis), etc.

PARTNER ORGANIZATIONS

To achieve this project the candidate will expend a secondment period in the ALBA synchrotron, more precisely in the XALOC line to develop single crystal diffraction coupled to a gas cell (NO2, H2O and other volatile organic compounds as methanol and ethanol).


Additionally, and in case of agreement, the candidate will also travel to the Advanced Light Source in Berkeley to perform advanced training in single crystal diffraction under external perturbation (local host: Dr Simon J. Teat). One of the PI has beamline allocated to measure SCO-MOF in 2022.

Figure 1. (a) Structure of H2N-BDC-Ln MOFs featuring the BDC ligand structure (upper left), a dinuclear Ln cluster (upper right), and ligand coordination to the Ln ions (below). (b) Diagram of the energy levels of H2N-BDC and different Ln (Gd3+, Tb3+ and Eu3+). ET (solid lines) and back-transfer transitions (dashed lines), respectively, before (blue lines) and after (orange lines) NO2 binding are indicated. (c) Calculated energy of T1 of H2N-BDC vs charge transfer. (d) Illustration of the ligand/NO2 configuration used for the CASSCF/CASPT2 calculation. (e) PL quenching and enhancement in H2N-BDC-Tb and H2N-BDC-Eu respectively upon 5 ppm NO2 exposure.