Heterometallic node engineering of MOF-808 enables diverse frustrated Lewis pairs for efficient transfer hydrogenation of carbonyl compounds

Trace Sn incorporation enriches the solid FLP catalytic centers in MOF-808. • 5Sn-MOF-808 shows enhanced pore structure and abundant Lewis acid–base sites. • Zr/Sn-CUS and Zr/Sn-OH pairs cooperatively activate isopropanol and carbonyl substrates. • Sn doping lowers water-desorption and hydrogen-transfer energy barriers. • Heterometallic node engineering enables efficient CTH of carbonyl compounds. The construction of solid frustrated Lewis pair (FLP) catalysts and their application in catalytic transfer hydrogenation (CTH) have attracted considerable attention. A series of M-MOF-808 catalysts was constructed by introducing small amounts of tetravalent heterometal ions into the metal cluster nodes of MOF-808. Among them, 5Sn-MOF-808 exhibited a more developed pore structure, a higher density of Lewis acid sites, and enhanced Lewis basicity, leading to excellent performance in the CTH of a range of carbonyl compounds. Systematic in-situ characterizations, poisoning experiments, and DFT calculations collectively reveal that Sn incorporation induces the formation of high-density and structurally diverse frustrated Lewis pair sites. These sites consist of Zr/Sn coordinatively unsaturated sites (CUS) and adjacent Zr/Sn–OH groups. Such FLP sites cooperatively promote isopropanol activation, carbonyl polarization, and reactive hydrogen transfer. In addition, Sn incorporation lowers the energetic cost for coordinated water desorption and active-site generation. This work establishes a structural correlation between heterometallic node modulation and solid FLP construction in MOFs, providing a rational strategy for designing efficient transfer hydrogenation catalysts. Download: Download high-res image (203KB) Download: Download full-size image