Zirconium-Based Catalysts in Organic Synthesis

Zirconium is a silvery-white malleable and ductile metal at room temperature with a crustal abundance of 162 ppm. Its compounds, showing Lewis acidic behavior and high catalytic performance, have been recognized as a relatively cheap, low-toxicity, stable, green, and efficient catalysts for various important organic transformations. Commercially available inorganic zirconium chloride was widely applied as a catalyst to accelerate amination, Michael addition, and oxidation reactions. Well-designed zirconocene perfluorosulfonates can be applied in allylation, acylation, esterification, etc. N-Chelating oganozirconium complexes accelerate polymerization, hydroaminoalkylation, and CO₂ fixation efficiently. In this review, the applications of both commercially available and synthesized zirconium catalysts in organic reactions in the last 5 years are highlighted. Firstly, the properties and application of zirconium and its compounds are simply introduced. After presenting the superiority of zirconium compounds, their applications as catalysts to accelerate organic transformations are classified and presented in detail. On the basis of different kinds of zirconium catalysts, organic reactions accelerated by inorganic zirconium catalysts, zirconium catalysts bearing Cp, and organozirconium catalysts without Cp are summarized, and the plausible reaction mechanisms are presented if available.

Amberlyst-15 supported zirconium sulfonate as an efficient catalyst for Meerwein-Ponndorf-Verley reductions

The Meerwein-Ponndorf-Verley (MPV) reaction is an important chemoselective route for carbonyl group hydrogenation, and thus designing new and effective catalysts for this transformation remains important and challenging. In this work, a new sulfonate coordinated Zr(IV) catalyst was prepared by the coordination of Zr(IV) onto the sulfonate groups of Amberlyst-15, which can effectively catalyze the MPV reaction and quantitatively convert carbonyl compounds to the corresponding alcohols with high reactivity and stability. Detailed mechanistic investigations reveal that the catalytic performance of Zr-AIER can be attributed to the synergetic effect between Zr⁴⁺ and the sulfonate group, and the porous structure with high surface area.

Selective hydrogenation of butyl levulinate to γ-valerolactone over sulfonated activated carbon-supported SnRuB bifunctional catalysts

The sulfonated activated carbon (SAC) supported SnRuB catalyst was developed through the co-impregnation followed by a chemical reduction process and applied for BL hydrogenation to GVL for the first time.

Hydrophobic species-enabled acid–base multi-catalysis for stereoselective access to renewable trans-anethole

A green and sustainable route was developed to stereoselectively produce biomass-based trans-AN (90% selectivity) over an acid–base bifunctional catalyst through cascade transfer hydrogenation and dehydration.

Recyclable Zr/Hf-Containing Acid-Base Bifunctional Catalysts for Hydrogen Transfer Upgrading of Biofuranics: A Review

The massive burning of a large amount of fossil energy has caused a lot of serious environmental issues (e.g., air pollution and climate change), urging people to efficiently explore and valorize sustainable alternatives. Biomass is being deemed as the only organic carbon-containing renewable resource for the production of net-zero carbon emission fuels and fine chemicals. Regarding this, the selective transformation of high-oxygen biomass feedstocks by catalytic transfer hydrogenation (CTH) is a very promising strategy to realize the carbon cycle. Among them, the important Meerwein-Ponndorf-Verley (MPV) reaction is believed to be capable of replacing the traditional hydrogenation strategy which generally requires high-pressure H2 and precious metals, aiming to upgrade biomass into downstream biochemical products and fuels. Employing bifunctional heterogeneous catalysts with both acidic and basic sites is needed to catalyze the MPV reaction, which is the key point for domino/cascade reaction in one pot that can eliminate the relevant complicated separation/purification step. Zirconium (Zr) and hafnium (Hf), belonging to transition metals, rich in reserves, can demonstrate similar catalytic efficiency for MPV reaction as that of precious metals. This review introduced the application of recyclable heterogeneous non-noble Zr/Hf-containing catalysts with acid-base bifunctionality for CTH reaction using the safe liquid hydrogen donor. The corresponding catalysts were classified into different types including Zr/Hf-containing metal oxides, supported materials, zeolites, metal-organic frameworks, metal-organic hybrids, and their respective pros and cons were compared and discussed comprehensively. Emphasis was placed on evaluating the bifunctionality of catalytic material and the key role of the active site corresponding to the structure of the catalyst in the MPV reaction. Finally, a concise summary and prospect were also provided centering on the development and suggestion of Zr/Hf-containing acid-base bifunctional catalysts for CTH.