Two-dimensional
covalent organic frameworks (2D-COFs) are a class
of crystalline porous organic polymers that consist of covalently
linked, two-dimensional sheets that can stack together through noncovalent
interactions. Here we report the synthesis of a novel COF, called
PyCOFamide, which has an experimentally observed pore size that is
greater than 6 nm in diameter. This is among the largest pore size
reported to date for a 2D-COF. PyCOFamide exhibits permanent porosity
and high crystallinity as evidenced by the nitrogen adsorption, powder
X-ray diffraction, and high-resolution transmission electron microscopy.
We show that the pore size of PyCOFamide is large enough to accommodate
fluorescent proteins such as Superfolder green fluorescent protein
and mNeonGreen. This work demonstrates the utility of noncovalent
structural reinforcement in 2D-COFs to produce larger and persistent
pore sizes than previously possible.
Natural and laboratory-guided evolution has created a rich diversity of fluorescent protein (FP)-based sensors for chloride (Cl−). To date, such sensors have been limited to the Aequorea victoria green fluorescent...
Nuclear magnetic resonance (NMR) spectroscopy is vital to synthesis and provides rich problem-solving opportunities to organic chemistry students. Using the theories of scaffolding, interleaving, and blocking, our research systematically explores how textbooks introduce and reinforce spectral features when teaching students to solve 1H NMR spectroscopy problems. Specifically, we investigated the 1H NMR spectral features presented in worked examples and practice problems across four undergraduate organic chemistry textbooks. We examined the frequency and ordering of spectral features to explore how the textbooks could support scaffolded instruction. Spectral features like the number of signals and chemical shift were covered by problems more frequently, while integration was covered least. Our findings suggest that textbooks do not provide sufficient practice with all 1H NMR spectral features. We observed no discernible pattern in how textbooks ordered spectral features of 1H NMR in problems, indicating that there is little systematic method to the design of textbook chapters. Implications for textbook authors and editors, instruction, and research are discussed.
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