Despite their record-breaking sorption capacities, metal–organic frameworks (MOFs) have rarely been used for the immobilization of homogeneous catalysts by simple absorption from solution. Here we demonstrate that this simple strategy allows successful immobilization of olefin metathesis catalysts inside MOFs. Ruthenium alkylidene complexes bearing ammonium-tagged NHC ligands were successfully supported inside (Al)­MIL-101-NH2·HCl. The materials thus obtained are true heterogeneous catalysts, active toward various substrates with TONs up to 8900 (in batch conditions) or 4700 (in continuous flow). Although the catalysts were held inside the MOF by noncovalent forces only, leaching was not observed and heavy metal contamination of the products was found to be below the detection limit of ICP MS (0.02 ppm). The robustness of the catalyst attachment allowed their use in a continuous flow setup.

A simple strategy for noncovalent immobilization of an olefin metathesis catalyst inside a (Cr)­MIL-101-SO3Na metal–organic framework (MOF) was presented. The olefin metathesis active corean alkylidene complex bearing an ammonium-tagged NHC ligand (Apeiron’s FixCat)was immobilized by ion exchange facilitated by the use of crown ether. The hybrid material thus obtained was shown with a number of model substrates to exhibit high activity and selectivity in a wide range of solvents. Next, selected polyfunctional pharmaceutically related substrates were transformed using 0.8–0.5 mol % of the Ru@MOF in polar solvents such as acetone and dimethyl carbonate, making this technology interesting in the context of green solvent utilization.

The first successful immobilization of a transition-metal catalyst inside MOFs by an acid−base reaction has been described. Simple absorption of a commercially available, amino-tagged, Hoveyda−Grubbs type ruthenium olefin metathesis catalyst inside an easy to make, Brønsted acidic MOF, (Cr)MIL-101-SO 3 H, yields a heterogeneous catalyst, which is stable even in very polar, "green" solvents, such as dimethyl carbonate and 2-propanol. The catalyst gives essentially ruthenium-free products upon simple filtration.

A versatile method for the post-synthetic removal of primary amino groups from metal-organic frameworks (MOFs) has been developed. The method allowed the first successful synthesis of the missing parent compound of an important family of MOFs - the unsubstituted (Al)MIL-101. The material was shown to be a useful reference compound for the elucidation of the role of amino groups in the adsorption and deactivation of olefin metathesis catalysts. The chemoselectivity of the deamination is sufficient for the selective removal of NH substituents from mixed-linker MOFs bearing both NH and RCONH groups.

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