It has been reported that the biological functions of enzymes could be altered when they are encapsulated in metal–organic frameworks (MOFs) due to the interactions between them. Herein, we probed the interactions of catalase in solid and hollow ZIF-8 microcrystals. The solid sample with confined catalase is prepared through a reported method, and the hollow sample is generated by hollowing the MOF crystals, sealing freestanding enzymes in the central cavities of hollow ZIF-8. During the hollowing process, the samples were monitored by small-angle X-ray scattering (SAXS) spectroscopy, electron microscopy, powder X-ray diffraction (PXRD), and nitrogen sorption. The interfacial interactions of the two samples were studied by infrared (IR) and fluorescence spectroscopy. IR study shows that freestanding catalase has less chemical interaction with ZIF-8 than confined catalase, and a fluorescence study indicates that the freestanding catalase has lower structural confinement. We have then carried out the hydrogen peroxide degradation activities of catalase at different stages and revealed that the freestanding catalase in hollow ZIF-8 has higher activity.

An oxidative linker cleaving (OLC) process was developed for surgical manipulation of the engraving process within single crystalline MOFs particles. The strategy relies on selective degradation of 2,5-dihydroxyterephthalic acid linker into small molecular fragments by oxidative ring-opening reactions, resulting in controllable scissoring of framework. By regulation of the generation and diffusion of oxidative species, the core MOFs will undergo divergent etching routes, producing a series of single crystalline hollow and yolk–shell MOF structures. In addition, the OLC process can be initiated and localized around the pre-embedded Pd NPs through on-site catalytic generation of oxidative species, leading to solitary confinement of multiple NPs within one single crystalline MOF particle, namely, a multi-yolk–shell structure. This unique architecture can effectively protect NPs from agglomeration while realizing size selective catalysis at the same time.

A one-pot transition metal-free method for synthesizing benzo[4,5]imidazo[1,2-a]quinazoline and imidazo[1,2-a]quinazoline derivatives has been developed. The approach is widely applicable to 2-fluoro-, 2-chloro-, 2-bromo- and 2-nitro-substituted aryl aldehyde and ketone substrates. The fluorescence properties of target compounds were studied.

Applying metal–organic frameworks (MOFs) on the surface of other materials to form multifunctional materials has recently attracted great attention; however, directing the MOF overgrowth is challenging due to the orders of magnitude differences in structural dimensions. In this work, we developed a universal strategy to mediate MOF growth on the surface of metal nanoparticles (NPs), by taking advantage of the dynamic nature of weakly adsorbed capping agents. During this colloidal process, the capping agents gradually dissociate from the metal surface, replaced in situ by the MOF. The MOF grows to generate a well-defined NP-MOF interface without a trapped capping agent, resulting in a uniform core–shell structure of one NP encapsulated in one single-crystalline MOF nanocrystal with specific facet alignment. The concept was demonstrated by coating ZIF-8 and UiO-66-type MOFs on shaped metal NPs capped by cetyltrimethylammonium surfactants, and the formation of the well-defined NP-MOF interface was monitored by spectroscopies. The defined interface outperforms ill-defined ones generated via conventional methods, displaying a high selectivity to unsaturated alcohols for the hydrogenation of an α,β-unsaturated aldehyde. This strategy opens a new route to create aligned interfaces between materials with vastly different structural dimensions.

Metal–organic frameworks (MOFs) is a promising class of sorbent materials for swing adsorption gas separation. However, although sorption kinetics plays a major role in column breakthrough experiments, it is rarely studied with MOF materials. This is largely because the synthesis of uniform yet separation-relevant MOFs is a challenging task. Here, we report a dual-modulation approach for the synthesis of well-defined Mg-MOF-74 hexagonal rods with an extremely uniform size distribution (polydispersity index = 1.02). Through epitaxial growth and wet chemical etching, uniform hollow Ni-MOF-74 with plate-shaped caps were obtained. CO2 adsorption kinetic study shows that hollow Ni-MOF-74 exhibits 54% faster diffusion rate compared to solid Ni-MOF-74 due to a shortened diffusion length, despite their identical CO2 uptake capacity. This has led to a 21% extension of column breakthrough time during CO2/N2 separation under identical conditions.