Metal-Organic Framework Anchored with a Lewis Pair as a New Paradigm for Catalysis

Abstract

Lewis pairs (LPs), classical and frustrated, have been successfully introduced into and stabilized in a metal-organic framework (MOF). Benefiting from the robust framework and tunable porous structure of MOFs, the resultant MOF-LP demonstrates not only great recyclability but also excellent performance in the catalytic reduction of imines and hydrogenation of alkenes. The combination of LP and MOF therefore lays a foundation for developing a MOF-LP as a new paradigm for catalysis, particularly heterogeneous catalysis.

Functional Macro‐Microporous Metal–Organic Frameworks for Improving the Catalytic Performance

“…Featuring macropores that facilitate molecular diffusion and expose more active sites, Pt/M‐ZIF‐8 is a good candidate for two‐steps catalytic reaction. The Knoevenagel condensation–hydrogenation reaction, i.e., Knoevenagel condensation of the p‐nitrobenzaldehyde and malononitrile catalyzed by the base active sites on ZIF‐8 as well as the hydrogenation process from NO 2 to NH 2 by employing Pt as the catalyst, was taken as an example to study the enhanced performance of Pt/M‐ZIF‐8 in the two‐steps catalytic reaction . For the first step, the Knoevenagel condensation reactions were carried out at room temperature under nitrogen (N 2 ) atmosphere in tetrahydrofuran solvent for 1.5 h. The Knoevenagel condensation reactions catalyzed by Pt/ZIF‐8 exhibited a conversion of 86.5%, whereas it reached 97.3% when the catalyst was Pt/M‐ZIF‐8 ( Figure ).…”

In Situ Formation of Frustrated Lewis Pairs in a Water‐Tolerant Metal‐Organic Framework for the Transformation of CO2

“…It is worth noting that our approach is distinct to that reported by Ma and co-workers,w ho incorporated LPs within MIL-101-Cr III by post-synthetic modification. [25] Powder X-ray diffrac-tion (PXRD) confirmed the purity of SION-105,which is also stable after immersion in water for 24 hours (Supporting Information, Figure S1). Thermogravimetric analysis (TGA) revealed the stability of SION-105 at temperatures up to 300 8 8C, followed by the loss of DMF lattice solvents within the pores (Supporting Information, Figure S2).…”

Promoting Frustrated Lewis Pairs for Heterogeneous Chemoselective Hydrogenation via the Tailored Pore Environment within Metal–Organic Frameworks

“…It remains as ignificant challenge for FLP catalysts to selectively hydrogenate a,b-unsaturated organic compounds to afford the relevant olefin product especially in heterogeneous systems. [11] Thediverse yet tunable features of MOFs [12] make them an efficient platform to manipulate heterogeneous catalysts for various organic transformations that traditional porous materials simply cannot provide. [11] Thediverse yet tunable features of MOFs [12] make them an efficient platform to manipulate heterogeneous catalysts for various organic transformations that traditional porous materials simply cannot provide.…”

“…[10] Recently,wedemonstrated the introduction of Lewis pair (LP) into metal-organic frameworks (MOFs), which exhibited enhanced stability and excellent recyclability,a swell as interesting catalysis performance for imine reduction reactions and hydrogenation of olefins. [11] Thediverse yet tunable features of MOFs [12] make them an efficient platform to manipulate heterogeneous catalysts for various organic transformations that traditional porous materials simply cannot provide. [13] On the basis of our recent success,w eenvisaged using FLPs for heterogeneous chemoselective hydrogenation of a,b-unsaturated organic compounds,and thus we postulate that the MOF pore environment can be delicately tailored with "ports" to anchor FLPs,meanwhile "activation" groups preferably interact with the targeted double bond in the substrate,t hereby producing selective reduction during the hydrogenation process (Scheme 1).…”

“…MIL-101(Cr)-FLP-H 2 (1.0 mmol FLP per 1gMIL-101(Cr) or 0.34 FLP per unsaturated Cr site) was used in the following characterizations. 11 BNMR spectroscopy measurements were carried out to investigate the FLP with activated hydrogen that is anchored on the pore wall of MIL-101(Cr)-FLP-H 2 .A ss hown in Figure 1a,the 11 BNMR spectrum of the mixture of B(C 6 F 5 ) 2 (Mes) and DABCO shows ap eak at 66.1 ppm, indicative of an extremely weak interaction between the Lewis acid and Lewis base.A fter treating the Lewis acid with MIL-101(Cr)-LB in toluene under 10 bar H 2 atmosphere and at room temperature for 24 h, the solid-state 11 BNMR spectrum showed ad istinct peak at À22.4 ppm, which is comparable to that of the homogeneous [HDABCO] + [HB(C 6 F 5 ) 2 (Mes)] À (d = À22.5 ppm) and related [HB(C 6 F 5 ) 2 (Mes)][LB] system (d = À22.1 ppm), thus confirming the formation of the presumed ammonium hydridoborate of FLP. [9a] Fur-thermore,t he peaks from the solid-state 19 FNMR spectrum ( Figure S1) of MIL-101(Cr)-FLP-H 2 are consistent with the formation of at etracoordinate anionic borate,f urther confirming the existence of FLP ammonium hydridoborate within the MOF.…”