Zhou Xianlong, Dong Juncai, Zhu Yihan, Liu Lingmei, Jiao Yan, Li Huan, Han Yu, Davey Kenneth, Xu Qiang, Zheng Yao, Qiao Shi-Zhang
School of Chemical Engineering and Advanced Materials, The University of Adelaide, Adelaide, South Australia 5005, Australia.
Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
J Am Chem Soc. 2021 May 5;143(17):6681-6690. doi: 10.1021/jacs.1c02379. Epub 2021 Apr 23.
A bottom-up chemical synthesis of metal-organic frameworks (MOFs) permits significant structural diversity because of various combinations of metal centers and different organic linkers. However, fabrication generally complies with the classic hard and soft acids and bases (HSAB) theory. This restricts direct synthesis of desired MOFs with converse Lewis type of metal ions and ligands. Here we present a top-down strategy to break this limitation via the structural cleavage of MOFs to trigger a phase transition using a novel "molecular scalpel". A conventional CuBDC MOF (BDC = 1,4-benzenedicarboxylate) prepared from a hard acid (Cu) metal and a hard base ligand was chemically cleaved by l-ascorbic acid acting as chemical scalpel to fabricate a new CuBDC structure composed of a soft acid (Cu) and a hard base (BDC). Controlled phase transition was achieved by a series of redox steps to regulate the chemical state and coordination number of Cu ions, resulting in a significant change in chemical composition and catalytic activity. Mechanistic insights into structural cleavage and rearrangement are elaborated in detail. We show this novel strategy can be extended to general Cu-based MOFs and supramolecules for nanoscopic casting of unique architectures from existing ones.
由于金属中心和不同有机连接体的各种组合，金属有机框架（MOF）的自下而上化学合成允许显著的结构多样性。然而，制备通常遵循经典的硬软酸碱（HSAB）理论。这限制了具有相反路易斯类型金属离子和配体的所需MOF的直接合成。在此，我们提出一种自上而下的策略，通过使用新型“分子手术刀”对MOF进行结构裂解以触发相变，从而打破这一限制。由硬酸（铜）金属和硬碱配体制备的传统CuBDC MOF（BDC = 1,4-苯二甲酸）被用作化学手术刀的L-抗坏血酸化学裂解，以制备由软酸（铜）和硬碱（BDC）组成的新CuBDC结构。通过一系列氧化还原步骤实现可控的相变，以调节铜离子的化学状态和配位数，从而导致化学成分和催化活性的显著变化。详细阐述了对结构裂解和重排的机理见解。我们表明，这种新颖的策略可以扩展到一般的铜基金属有机框架和超分子，用于从现有结构中纳米铸造独特的结构。
