The structure transformation of metal-organic frameworks (MOFs) is significant for expanding the MOF family and exploring new MOF properties; however, it remains a significant challenge. In this work, we showcase the structure transformation of an Hf-based MOF. This MOF, with different phases denoted as Hf-SDC(face-centered cubic (fcc)) and Hf-SDC(hexagonal close-packed (hcp)), was successfully synthesized under controlled synthesis conditions. Interestingly, we demonstrated that the obtained two different phase MOFs can be further transformed to amorphous Hf-SDC-Br(am) and semi-crystalline Hf-SDC-Br(sc) through a simple bromination reaction, which converts the rigid –C=C– bonds into flexible –C(Br)–C(Br)– bonds. Specifically, the three-dimensional fcc topology could no longer be maintained, and the interlayer order of the hcp topology was disrupted, resulting in the amorphous Hf-SDC-Br(am) and semi-crystalline Hf-SDC-Br(sc), respectively. Finally, as a proof-of-concept application, the semi-crystalline Hf-SDC-Br(sc) was used as a support to load with Pd nanoparticles, yielding a Pd/Hf-SDC-Br(sc) catalyst. Benefiting from the Br-Pd interaction and the retained partial structural order that facilitates mass transport of reactants, Pd/Hf-SDC-Br(sc) exhibited excellent catalytic performance in the conversion of vanillin to 2-methoxy-4-methylphenol, with a record turnover frequency of 1021 h⁻¹. This work demonstrates the feasibility of the structure transformation of MOF through simple chemical reaction and highlights the importance of the structure transformation of MOFs for advanced catalysis.

Hollow metal-organic frameworks (MOFs) have attracted increasing attention in the field of catalysis in recent years due to their unique cavity structure with fast mass-diffusion rates and easily accessible active sites. Here, we report the use of dynamic modulators, which are formed by the in-situ imine condensation reaction of 4-aminobenzoic acid and 4-formylbenzoic acid, to regulate the growth of MOFs to synthesize well-defined hollow thioether functionalized UiO-67 (denoted as H-UiO-67-S) single crystals. After supporting Pd nanoparticles, the designed catalysts Pd@H-UiO-67-S show excellent conversion (> 99.9%), selectivity (> 99.9%), and stability (10 cycles) in the selective hydrogenation of nitrobenzenes with other reducible groups. Density functional theory calculations and the experimental results reveal that Pd nanoparticles not only selectively adsorb the nitro-groups on nitrobenzene, but also restrict the adsorption of the aniline product, due to the interaction of thioether with Pd in the confined pores of H-UiO-67-S, finally result in a significant increase in selectivity of nitro-hydrogenation.

In the past decades, metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) basically enjoy the coordination chemistry and covalent chemistry, respectively, and such uniqueness has become the major obstacle hampering their further scope diversity and application multi-functionalization. Inspired from the principle of organic retrosynthesis, combining coordination bond and covalent bond together offers additional opportunities for constructing novel MOFs, COFs and MOF@COF hybrids as well as confer on them superior performances in versatile application fields. In this review, we firstly classify and summarize the recently reported synthesis strategies based on the integration of metal–ligand coordination and dynamic covalent bonds. Then, the application performances of as-constructed MOFs, COFs as well as MOF@COF hybrids are discussed and highlighted in the fields of adsorption, separation, catalysis, biosensing, energy storage and so on. Last, our personal insights of the remaining challenges and further prospects are also provided, in order to trigger much more inspirations and endeavors for this hot research field.

Photocatalysis, via conversion of light into valuable chemicals, is an economic and effective way to utilize inexhaustible solar energy for the sustainable development of our human society. Aiming at killing two birds with one stone, metal nanoparticle (MNP)/metal-organic framework (MOF) composites via integration of the individual advantages of MNP and MOF have been becoming a versatile photocatalyst. Moreover, owing to the synergist effect between each component, MNP/MOF composite photocatalysts usually show greatly promoted catalytic activity, selectivity and long-term recyclability. In this review, first of all, the widely adopted synthesis strategies of MNP/MOF composite are introduced comprehensively, and then their recent advances in photocatalysis including photocatalytic hydrogen production, carbon dioxide reduction, organic transformation reactions and photodegradation of pollutants are summarized and highlighted. Finally, challenges and perspectives among MNP/MOF based photocatalysis are also proposed and discussed for advancing further development in this hot research field.