Defects, which are commonly in metal organic frameworks (MOFs), are closely related to the performance of materials in various applications. Unlike other MOFs where metal ion clusters are usually 4-, 5-, or 6-connected to the organic linkers, one secondary building unit (SBU) of UiO-66 is coordinated by 12 Zr 6 clusters via 12 benzen-1,4-dicarboxlate (BDC) linkers. Therefore, the integrity of the structure can be well maintained after linker or even cluster missing. So far, many methods have been reported on the defect engineering of UiO-66 including adjusting the synthesis conditions (temperature, Zr/linker ratio and choice of Zr precursor), addition of modulators, thermal activation/dehydration, linker modification and metal cation substitution. Various techniques have been used and developed to characterize the existence and concentration of defects, though each technique has its limitations. The formation of defects not only changes the pore structure, but also brings beneficial changes in thermal, electronic, catalytic and adsorbing abilities; thus improved performance can be achieved when defective UiO-66 is used as Lewis and/or Bronsted acids, photocatalysts, adsorbents, electrodes or porous support. In this review, a comprehensive review of defect engineering for UiO-66 including their preparations, characterizations, applications, and then the challenges and outlook are discussed, aiming to provide some designing knowledge for the synthesis of defective UiO-66 with high-performance and promote the wide application of UiO-66 in various fields.
Smart hybrids of Zn2GeO4 nanoparticles and ultrathin g‐C3N4 layers (Zn2GeO4/g‐C3N4 hybrids) are realized by a facile solution approach, where g‐C3N4 layers act as an effective substrate for the nucleation and subsequent in situ growth of Zn2GeO4 nanoparticles. A synergistic effect is demonstrated on the two building blocks of Zn2GeO4/g‐C3N4 hybrids for lithium storage: Zn2GeO4 nanoparticles contribute high capacity and serve as spacers to isolate the ultrathin g‐C3N4 layers from restacking, resulting in expanded interlayer and exposed vacancies with doubly bonded nitrogen for extra Li‐ion storage and diffusion pathway; 2D g‐C3N4 layers, in turn, minimize the strain of particles expansion and prevent the formation of unstable solid electrolyte interphase, leading to highly reversible lithium storage. Benefiting from the remarkable synergy, the Zn2GeO4/g‐C3N4 hybrids exhibit highly reversible capacity of 1370 mA h g−1 at 200 mA g−1 after 140 cycles and excellent rate capability of 950 mA h g−1 at 2000 mA g−1. The synergistic effect originating from the hybrids brings out excellent electrochemical performance, and thus casts new light on the development of high‐energy and high‐power anode materials.
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