The development of well-defined multimetallic porous metal-organic frameworks (MOFs) will add a new dimension to the application of MOF catalysis. From this perspective, the understanding and tailoring of the catalytic metal sites in MOFs are key fundamental challenges that could reveal the intrinsic potential of these materials. In this work, a series of porphyrin-salen chiral MOFs (ps-CMOFs 2-7) have been synthesized through postsynthetic metalation (PSMet) of the parent ps-CMOF via single-crystal to single-crystal transformation. Crystal structures of these ps-CMOF analogues revealed the same topological structure but varied metal entities compared to those of the parent framework. Note that the PSMet process involves three methods involving cation exchange at the nodes, cation exchange at the metalated porphyrin, and cation addition at the free porphyrin, which has been systematically investigated using single-crystal X-ray diffraction and other physicochemical methods. The N adsorption tests, thermogravimetric analysis, and powder X-ray diffraction of 2-7 showed curves or patterns similar to those of 1, indicating the maintenance of the crystallinity, porosity, and thermal stability of the framework during the PSMet process. In addition, 2-7 showed distinctly improved adsorption capacities and isosteric heats of adsorption (Q) for CO compared to those of their parent counterpart. Lastly, as a representative example of the ps-CMOF catalytic platform, 5 proved to be an efficient recyclable heterogeneous catalyst for the asymmetric addition reaction of CO with epoxides under mild conditions. Furthermore, because of the constrained chiral environment within ps-CMOF, the enantioselectivity of this reaction appears to be dependent on substrate size.

Metal-organic frameworks (MOFs) imbedded privileged molecular catalysts are of particular interest due to their higher catalytic activities derived from the MOFs pore/channel confinement effect, improved lifetime through eliminating intermolecular deactivation pathway, and the recyclability based on their heterogeneity. In this work, a 3D chiral metallosalen-based MOF [Cd(Cu(salen))(DMF)]·DMF·3HO (1) with a 1D open channel was synthesized and characterized by single-crystal X-ray diffraction and other physicochemical methods. Upon postsynthetic reduction modification with NaBH, the conversion from imino to amino group on salen cores of 1 generates the reduction product 2 with a more flexible chiral group and more alkaline backbone, meanwhile still maintaining the original porous framework. 2 can be used as an efficient heterogeneous catalyst for the asymmetric Henry reaction with broad substrate applicability and exhibits higher activity and enantioselectivity (ee up to 98%) compared with the unreduced 1. Note that 2 can accelerate the Henry reaction of pyridine-2-carboxaldehyde possessing a potential coordination atom with excellent ee value; however, the homogeneous counterpart does not. In addition, the bulky aldehydes show a decrease in activity but almost the same enantioselectivity with an increase in the molecular size of substrates as a result of the chiral confinement effect of 2, indicating the size-dependent selectivity. To the best of our knowledge, this is the highest enantioselectivity for asymmetric Henry reaction catalyzed by MOF-based catalysts.

The engineering of highly stable metal–organic frameworks (MOFs) will unveil the intrinsic potential of these materials for practical applications, especially for heterogeneous catalyzes. However, it is fairly challenging to rationally design robust MOFs serving as highly effective and reusable heterogeneous catalysts. Here, for the first time, we report the construction of four robust UiO-type chiral zirconium–metallosalen frameworks, denoted ZSF-1–4. Single-crystal X-ray-diffraction reveals that the frameworks consist of twelve-connected Zr6O8 clusters with privileged chiral metallosalen ligands anchored at ideal positions, generating confined chiral cages that enable synergistic activation. Unlike UiO-68 that is highly sensitive to aqueous solutions, ZSF-1–4 exhibit excellent chemical stability in aqueous solutions with a wide range of pH owing to the abundant hydrophobic groups within metallosalen ligands. These features render ZSF-1 and ZSF-2 to be excellent recycled heterogeneous catalysts for the conversion of imitated industrial CO2 with epoxides into cyclic carbonates with the highest reported turnover numbers in Zr-MOFs. With regard to asymmetric catalysis, ZSF-3 and ZSF-4 can effectively catalyze C–H azidation reaction in water medium with ee value up to 94%. Moreover, these robust ZSFs can be further extended to other analogues with various metal centers through demetallization–remetallization strategy, which renders them to be an excellent platform for broader fields.

A three‐dimensional (3D) chiral metal–organic framework [Cd2{Ni(salen)}(DMF)3]·4DMF·7H2O (1) based on a new enantiopure tetracarboxyl‐functionalized metallosalen Ni(H4salen) {where H6salen is (R,R)‐N,N′‐bis[3‐tert‐butyl‐5‐(3,5‐dicarboxybenzyl)salicylidene]‐1,2‐diphenylethylenediame} was synthesized and characterized by infrared spectroscopy, thermogravimetric analysis, nitrogen and carbon dioxide adsorption, and powder and single‐crystal X‐ray diffractions. In 1, the dinuclear Cd2 cluster [Cd2(COO)4(DMF)3] as a node is cross‐linked by four isophthalate groups on the salen ligands, forming a 2D lamellar structure, which are further linked by Ni(salen) into the 3D network with a 1D open channel (ca. 7.0 × 8.0 Å2) along the a axis. On account of its porosity, Lewis acid sites, and moderate uptake for CO2, 1 can be used as an efficient heterogeneous catalyst for the CO2 cycloaddition with epoxides under relatively mild conditions. Moreover, the bulky epoxide shows a decrease in activity with an increase in the alkyl chain length of the substrate as a result of the confinement effect of 1, showing size‐dependent selectivity.

Objectives To explore the intervention mechanism of combining Polygala tenuifolia (PT) with Magnolia officinalis (MO) on gastrointestinal motility disorders caused by PT. Methods Urine and faeces of rats were collected; the effects of PT and MO on the gastric emptying and small intestine advancing rates in mice were analysed via ultra-high performance liquid chromatography–quadrupole time-of-flight mass spectrometry (UHPLC–Q-TOF-MS) to determine the potential metabolites. Changes in the metabolic profiles of the urine and faeces were revealed by untargeted metabolomics, followed by multivariate statistical analysis. The integration of urine and faeces was applied to reveal the intervention mechanism of PT–MO on PT-induced disorders. Key findings PT + MO (1:2) improved the gastrointestinal function in mice suffering from PT-induced gastrointestinal motility disorder. Metabolomics indicated that the PT–MO mechanism was mainly associated with the regulations of 17 and 12 metabolites and 11 and 10 pathways in urine and faeces, respectively. The common metabolic pathways were those of tyrosine, purine, tricarboxylic acid cycle, pyruvate and gluconeogenesis, which were responsible for the PT–MO intervention mechanism. Conclusions The PT–MO (1:2) couple mechanism mitigated the PT-induced disorders, which were related to the energy, amino acid and fatty metabolisms.