This review summarises the recent advances of covalent organic framework photocatalysts including structures and applications.

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Aiming for increased nickel and lower cobalt content in layered transition metal oxide cathodes (NCM) is a feasible strategy for achieving increased energy density and cost competitiveness in commercial lithium-ion batteries. However, the practical long-term cycling of NCM cathodes suffers from severe capacity degradation due to irreversible interface phase transformation and unavoidable crack formation. Herein, an in situ modification strategy is used to form a uniform and conformal Li 1.8 Sc 0.8 Ti 1.2 (PO 4 ) 3 (LSTP) protective layer by interconnecting the single-crystal-layered LiNi 0.6 Co 0.1 Mn 0.3 O 2 (SC-NCM) particles. LSTP surface modification helps to construct a robust cathode-electrolyte interphase thin film between the cathode and the electrolyte, which can prevent SC-NCM corrosion by electrolyte, and the stability of the mechanics can improve the intergranular cracks caused by long cycles under harsh conditions. Moreover, the LSTP conductive modification layer facilitates the lithium-ion transport among cathode particles, effectively enhancing the rate capability. Impressively, the LSTP modified SC-NCM exhibits a high reversible capacity of 144.3 mAh g −1 at the high discharge rate of 5 C and maintains a capacity retention of 90.27% even at the ultrahigh charge voltage of 4.6 V operation after 500 cycles. Moreover, in a pouch-type full battery, the graphite/LSTP modified SC-NCM maintains a capacity retention of 89.6% after 1700 cycles.

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One of vital issues that inhibit photoactivity of metal−organic frameworks is the poor electrical conductivity. In this work, one-dimensional mixed-valence iron chains are used to improve this poor situation in . A series of mixed-valence MIL-53(Fe) photocatalysts were obtained through heating at different temperatures in vacuum. The effect of Fe II coordinatively unsaturated metal sites (CUS) and one-dimensional mixed-valence iron chains on their photocatalytic property was discussed. The experimental results indicated that mixed-valence MIL-53(Fe) with a reference Fe II /Fe III ratio of 0.2725 displayed the best photocatalytic performance, which showed 96.28 and 95.01% removal efficiencies of RhB and TC-H in 100 min, respectively. Moreover, MIL-53(Fe) heated in vacuum displayed better catalytic activity than MIL-53(Fe) heated in air for RhB and TC-H degradation. Based on the analysis of various characterizations, the reinforced catalytic activity can be attributed to the charge mobilities in mixedvalence Fe II /Fe III chains. It is worth mentioning that the method is also applicable to MIL-88(Fe) and MIL-101(Fe). Additionally, mixed-valence MIL-53(Fe) can also perform the catalysis reaction in the nighttime by activating persulfate (PS) to produce free radicals. Interestingly, it was found that the Fe II CUS lost in activating PS can be supplemented by self-reduction of photogenerated electrons during illumination in the daytime, so as to achieve a more stable cycle. This work demonstrated that the photoactivity of MIL-53(Fe) can be improved by adjusting the ratio of Fe II /Fe III and the feasibility of using as an all-dayactive catalyst.