Asymmetric Hydrophosphonylation of Imines to Construct Highly Stable Covalent Organic Frameworks with Efficient Intrinsic Proton Conductivity

Abstract

Imine-linked covalent organic frameworks (COFs) have received widespread attention because of their structure features such as high crystallinity and tunable pores. However, the intrinsic reversibility of the imine bond leads to the poor stability of imine-linked COFs under strong acid conditions. Also, their thermal stability is significantly lower than that of many other COFs. Herein, we report for the first time that the reversible imine bonds in the skeleton of COFs can be locked through the asymmetric hydrophosphonylation reaction of phosphite. The functionalized COFs not only retain the crystallinity and porous structure but also exhibit evidently improved chemical and thermal stabilities. In addition, the phosphorous acid groups generated by acidic hydrolysis attached to the skeleton endow the COFs with good intrinsic proton conductivity. Due to the diversity of phosphite derivatives and imine-linked COFs, this work may provide an avenue for extending the COF structures and functions through the asymmetric hydrophosphonylation reaction.

A Universal Grain “Cage” to Suppress Halide Segregation of Mixed-Halide Inorganic Perovskite Solar Cells

“…There is an intense peak at 2θ = 2.33° in the powder X-ray diffraction (PXRD) pattern, as shown in Figure S4c, which is in good agreement with eclipsed stacking (AA, space group P 2) according to a previous report . Together with the disappearance of −NH 2 /CO characteristic peaks and the detection of the CN group at 1622 cm –1 (Figure S5), , we can confirm that PbBr 2 can effectively catalyze the COF polymerization with average pore size of 4.39 nm, which is similar to the calculated value of 4.19 nm (Figure S4d–f). Because of the presence of electron-donating groups in COFs, there will be a strong interaction between PbX 2 and the nitrogen-containing conjugated skeleton.…”

“…There is an intense peak at 2θ = 2.33°in the powder X-ray diffraction (PXRD) pattern, as shown in Figure S4c, which is in good agreement with eclipsed stacking (AA, space group P2) according to a previous report. 26 Together with the disappearance of −NH 2 /C�O characteristic peaks and the detection of the C�N group at 1622 cm −1 (Figure S5), 26,27 we can confirm that PbBr 2 can effectively catalyze the COF polymerization with average pore size of 4.39 nm, which is similar to the calculated value of of the strong Pb−X−Pb corner-sharing coordination interaction, 28 therefore creating a negatively charged center in the hexagonal pore (Figure S6). This can be cross-checked by the detection of Pb/Br signals and peak shift to lower binding energy from the X-ray photoelectron spectroscopy (XPS) spectra of the thoroughly washed COF sample (Figure S7) and ultraviolet−visible (UV−vis) absorption spectra (Figure S8).…”

Alkoxy phosphonic acid-functionalized conjugated microporous polymers for efficient and multi-environmental proton conduction

“…Furthermore, Alkoxy side chains and H 3 PO 4 molecules are highly dynamic and mobile integrating with the hydrophilic side chains and the hydrophobic skeleton promote the microphase separation inside the CMPs, thus side chains prompt phosphonic acid groups move close to H 2 O molecules and form hydrated protons, and by the rotation of H 3 PO 4 molecules, protons can hop across the hydrogenbonding networks, promoting the mobility of protons. 26,80,81 View Article Online…”

Sulfonated covalent organic framework packed Nafion membrane with high proton conductivity for H2/O2fuel cell applications

“…Owing to the high-power density, safety, portability, and clean and efficient energy utilization technology, proton exchange membrane fuel cells (PEMFCs) showed great prospects in solving energy shortages and environmental pollution. [1][2][3][4][5][6][7][8][9][10] In this respect, constructing fuel cells with outstanding performance via proton-conducting material design is essential and urgent. At present, the Naon proton exchange membrane from Dupont is widely used in fuel cells due to its good mechanical strength, high proton conductivity in a full water state, and long service life.…”