RESUMO
We examine the growth rates, activation energies, and hydrolytic stability of multiple 2D boronate ester covalent organic frameworks by turbidity measurements, observing a 200-fold range in stability. The rate-determining step in boronate ester 2D COF growth is not in-solution condensation, but rather interlayer polymer stacking through a nucleation-elongation process.
RESUMO
A conjugated porous polymer (CPP) that exhibits fluorescence quenching when exposed to TNT vapor was synthesized via a Sonaogashira cross-coupling reaction. Two polymerization solvents, DMF and PhMe, and two activation procedures, evacuation and lyophilization, were evaluated to optimize the response of the CPP to TNT vapor. Key differences in surface area and absorption were seen as a function of polymerization solvent and activation procedure. The polymer synthesized in DMF and activated by lyophilization had the highest surface area and the strongest response to TNT vapor. This paper demonstrates the importance of growth and activation conditions in optimizing the porosity and sensing performance of CPPs.
RESUMO
Two-dimensional layered covalent organic frameworks (2D COFs) organize π-electron systems into ordered structures ideal for exciton and charge transport and exhibit permanent porosity available for subsequent functionalization. A 2D COF with the largest pores reported to date was synthesized by condensing 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) and 4,4'-diphenylbutadiynebis(boronic acid) (DPB). The COF was prepared as both a high surface area microcrystalline powder as well as a vertically oriented thin film on a transparent single-layer graphene/fused silica substrate. Complementary molecular dynamics and density functional theory calculations provide insight into the interlayer spacing of the COF and suggest that adjacent layers are horizontally offset by 1.7-1.8 Å, in contrast to the eclipsed AA stacking typically proposed for these materials.
