Allosteric Modulation toward Nonionic Covalent Organic Framework Nanosheets
Hao Deng, Ying Wang, Yanqiu Lü, Zhong Gao, Yong Zhu, Bohui Lyu, Ziting Zhu, Kaiyu Wang, Febrian Hillman, Sui Zhang, Runnan Zhang, Zhongyi Jiang
Abstract
Nonionic covalent organic framework nanosheets (nCOFNs) are new-generation building blocks for diverse applications. However, the solution-phase synthesis of highly crystalline, large-sized nCOFNs remains particularly challenging, as it requires the simultaneous regulation of chemical interactions for intralayer framework construction and physical interactions for interlayer stacking. Allostery, a ubiquitous natural process for regulating the structure and activity of biomacromolecules, awaits exploration in synthetic functional materials. Herein, we showcase an allosteric modulation strategy for the solution-phase synthesis of β-ketoenamine-linked nCOFNs. The secondary amine, as an allosteric modulator, facilitates enol-keto tautomerization reversibility, affording allosteric activation for in-plane assembly, while its steric hindrance affords allosteric inhibition for out-of-plane assembly. The modulator with a high N exposure factor and moderate-size side groups can achieve an optimal balance between two allosteric effects. Consequently, a series of high-quality nCOFNs with high crystallinity and aspect ratios exceeding 1000 can be mildly synthesized under ambient conditions with yields of up to 82%. The excellent solution processability of nCOFNs enables their facile assembly into membranes that exhibit ultrahigh methanol permeance of 127 L m –2 h –1 bar –1, superior durability in continuous filtration for over 1000 h, and high efficiency in purifying high-value pharmaceuticals. Furthermore, we demonstrate the practical application potential by assembling nCOFNs into large-area flat-sheet (∼430 cm 2 ) and hollow fiber membranes.