RESUMO
The chemistry of metal-organic frameworks (MOFs) has the potential to introduce high school and undergraduate students to the fundamental chemical principles of structure and bonding, enhance the development of skills in synthesis and crystal growth, and promote hands-on experience with gas capture and host-guest chemistry of emerging materials with desirable environmental applications. However, most available experiments in the pedagogical literature involving MOFs require laboratory equipment and the use of hazardous chemicals to facilitate crystal growth and the study of structure-property relationships. To remedy this gap in the literature, this paper describes an adapted experimental approach designed specifically for a household environment or low-resource laboratory to grow, activate, and use cyclodextrin-based MOFs for CO2 uptake. This experiment implements a simple procedure that can be carried out safely without access to specialized equipment or laboratory infrastructure. Despite the simplicity of the experimental design, this experiment presents an intellectually engaging opportunity for high school and undergraduate students to explore crystal growth and nucleation, coordination chemistry, and host-guest chemistry as well as green chemistry concepts such as the choice of benign reagents and solvents, and applications of porous materials for gas uptake.
RESUMO
This paper identifies the electrochemical properties of individual facets of anisotropic layered conductive metal-organic frameworks (MOFs) based on M3(2,3,6,7,10,11-hexahydroxytriphenylene)2 (M3(HHTP)2) (M = Co, Ni). The electroanalytical advantages of each facet are then applied toward the electrochemical detection of neurochemicals. By employing epitaxially controlled deposition of M3(HHTP)2 MOFs on electrodes, the contribution of the basal plane ({001} facets) and edge sites ({100} facets) of these MOFs can be individually determined using electrochemical characterization techniques. Despite having a lower observed heterogeneous electron transfer rate constant, the {001} facets of the M3(HHTP)2 systems prove more selective and sensitive for the detection of dopamine than the {100} facets of the same MOF, with the limit of detection (LOD) of 9.9 ± 2 nM in phosphate-buffered saline and 214 ± 48 nM in a simulated cerebrospinal fluid. Langmuir isotherm studies accompanied by all-atom MD simulations suggested that the observed improvement in performance and selectivity is related to the adsorption characteristics of analytes on the basal plane versus edge sites of the MOF interfaces. This work establishes that the distinct crystallographic facets of 2D MOFs can be used to control the fundamental interactions between analyte and electrode, leading to tunable electrochemical properties by controlling their preferential orientation through self-assembly.