Ko, Michael
Submitted to the Faculty in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry.
DISSERTATION ABSTRACT:
Since the discovery of electrically conductive two-dimensional (2D) metal–organic frameworks (MOFs), the synthetically tunable properties and intrinsic porosity of these materials make them promising for multifunctional sensing devices. The focus of my work is on a class of 2D MOFs based on a triphenylene core (2,3,6,7,10,11- hexahydroxytriphenylene, HHTP and 2,3,6,7,10,11-hexaiminotriphenylene, HITP) coordinating to divalent Cu or Ni metal nodes forming M3HXTP2 MOF analogs (M = Ni, Cu; X = NH, HITP or O, HHTP). Chapter 2 describes a simple strategy for device fabrication, using mechanical abrasion, enabling the chemiresistive sensing of NH3, H2S, and NO. The value in this contribution is threefold. First, the technique may be applicable to a wide range of materials, both semiconductors and possibly insulators. Second, the rapid prototyping method enables direct deposition using mechanical abrasion on a wide range of substrates. Third, the integration of the MOF-based sensing material into devices is entirely solvent-free, which can preserve device substrates sensitive to harsh solvents. Chapter 3 describes a new strategy of MOF synthesis termed oxidative restructuring that feature several innovative characteristics that advance the field of MOF integration. First, oxidative restructuring enables the facile integration of Cu3HHTP2 and Cu-BTC onto prepatterned Cu layer on multiple substrates. Second, we detail spectroscopic evidence that provides insight into the interaction between Cu3HHTP2 and NO using diffuse reflectance infrared fourier transform spectroscopy and X-ray photoelectron spectroscopy. Third, Cu3HHTP2 MOF devices demonstrated the highest dynamic loading capacity of NO and functioned as chemiresistive sensors for the detection of NO and H2S. Chapter 4 describes the implementation of 2D MOF based electrodes to enable the voltammetric detection of biologically relevant analytes. First, strategic selection of redox active analytes combined with the electrochemical methods, allowed us to investigate the intrinsic electrochemical properties of M3HXTP2 MOF analogs (M = Ni, Cu; X = NH, HITP or O, HHTP). Second, this demonstrated one of the first uses of 2D MOFs in solution phase detection with nanomolar detection at 63 ± 11 nM for dopamine and 40 ± 17 nM for serotonin. Taken together, chapters 1-4 advance the field of conductive metal–organic frameworks by providing insight in molecular engineering of MOFs that guides the iii structure property relationships to enable precise function for chemical detection and provides strategies for the strategic integration of MOFs on substrates.