Browsing by Author "Zhai, Tianshu"

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    Superior mechanical properties of multilayer covalent-organic frameworks enabled by rationally tuning molecular interlayer interactions
    (PNAS, 2023) Fang, Qiyi; Pang, Zhengqian; Ai, Qing; Liu, Yifeng; Zhai, Tianshu; Steinbach, Doug; Gao, Guanhui; Zhu, Yifan; Li, Teng; Lou, Jun
    Two-dimensional (2D) covalent-organic frameworks (COFs) with a well-defined and tunable periodic porous skeleton are emerging candidates for lightweight and strong 2D polymeric materials. It remains challenging, however, to retain the superior mechanical properties of monolayer COFs in a multilayer stack. Here, we successfully demonstrated a precise layer control in synthesizing atomically thin COFs, enabling a systematic study of layer-dependent mechanical properties of 2D COFs with two different interlayer interactions. It was shown that the methoxy groups in COFTAPB-DMTP provided enhanced interlayer interactions, leading to layer-independent mechanical properties. In sharp contrast, mechanical properties of COFTAPB-PDA decreased significantly as the layer number increased. We attributed these results to higher energy barriers against interlayer sliding due to the presence of interlayer hydrogen bonds and possible mechanical interlocking in COFTAPB-DMTP, as revealed by density functional theory calculations.
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    Ultrahigh resistance of hexagonal boron nitride to mineral scale formation
    (Springer Nature, 2022) Zuo, Kuichang; Zhang, Xiang; Huang, Xiaochuan; Oliveira, Eliezer F.; Guo, Hua; Zhai, Tianshu; Wang, Weipeng; Alvarez, Pedro J.J.; Elimelech, Menachem; Ajayan, Pulickel M.; Lou, Jun; Li, Qilin; NSF Nanosystems Engineering Research Center Nanotechnology-Enabled Water Treatment
    Formation of mineral scale on a material surface has profound impact on a wide range of natural processes as well as industrial applications. However, how specific material surface characteristics affect the mineral-surface interactions and subsequent mineral scale formation is not well understood. Here we report the superior resistance of hexagonal boron nitride (hBN) to mineral scale formation compared to not only common metal and polymer surfaces but also the highly scaling-resistant graphene, making hBN possibly the most scaling resistant material reported to date. Experimental and simulation results reveal that this ultrahigh scaling-resistance is attributed to the combination of hBN’s atomically-smooth surface, in-plane atomic energy corrugation due to the polar boron-nitrogen bond, and the close match between its interatomic spacing and the size of water molecules. The latter two properties lead to strong polar interactions with water and hence the formation of a dense hydration layer, which strongly hinders the approach of mineral ions and crystals, decreasing both surface heterogeneous nucleation and crystal attachment.