Nanoparticle/metal–organic frameworks (MOF) based composites have recently attracted significant attention as a new class of catalysts. Such composites possess the unique features of MOFs (including clearly defined crystal structure, high surface area, single site catalyst, special confined nanopore, tunable, and uniform pore structure), but avoid some intrinsic weaknesses (like limited electrical conductivity and lack in the “conventional” catalytically active sites). This review summarizes the developed strategies for the fabrication of nanoparticle/MOF composites for catalyst uses, including the strategy using MOFs as host materials to hold and stabilize the guest nanoparticles, the strategy with subsequent MOF growth/assembly around pre-synthesized nanoparticles and the strategy mixing the precursors of NPs and MOFs together, followed by self-assembly process or post-treatment or post-modification. The applications of nanoparticle/MOF composites for CO oxidation, CO₂ conversion, hydrogen production, organic transformations, and degradation of pollutants have been discussed. Superior catalytic performances in these reactions have been demonstrated. Challenges and future developments are finally addressed.

Excessive carbon dioxide (CO₂) emissions have been subject to extensive attention globally, since an enhanced greenhouse effect (global warming) owing to a high CO₂ concentration in the atmosphere could lead to severe climate change. The use of solar energy and other renewable energy to produce low‐cost hydrogen, which is used to reduce CO₂ to produce bulk chemicals such as methanol, is a sustainable strategy for reducing carbon dioxide emissions and carbon resources. CO₂ conversion into methanol is exothermic, so that low temperature and high pressure are favorable for methanol formation. CO₂ is usually captured and recovered in the liquid phase. Herein, the emerging technologies for the hydrogenation of CO₂ to methanol in the condensed phase are reviewed. The development of homogeneous and heterogeneous catalysts for this important hydrogenation reaction is summarized. Finally, mechanistic insight on CO₂’s conversion into methanol over different catalysts is discussed by taking the available reaction pathways into account.

Aromatic hydrocarbons as a liquid fuel have unique combustion properties (high volume energy density, etc.). Thus preserving the aromatic rings while selectively cleaving the C–O bonds in the hydrodeoxygenation of lignin derived substituted phenols without additional consumption of H₂ is of crucial importance. In this regard, the composite materials, which are used as the catalyst support, were prepared through the hybridization of Nb₂O₅ (niobium oxide) with MC (micro–mesoporous carbon). Ru NPs (nanoparticles) were loaded on the Nb₂O₅-MC composite supports by the incipient wetness impregnation method. And then the as-synthesized catalysts were characterized by various techniques, including XRD, SEM, TEM, BET, NH₃-TPD, XPS, etc. Under mild conditions (200–250 °C and 2.0–10 bar H₂), the Ru/Nb₂O₅-MC catalyst was proved to be highly effective for the hydrodeoxygenation (HDO) of phenol. With regard to achieving a high selectivity to benzene, the biphasic catalytic process in the decalin/water mixed solvent was superior to the monophasic processes in either the decalin or water solvent under the same conditions. Water acted as a co-solvent that prevented the occurrence of side reactions and promoted the catalytic C–O bond scission of phenol. The synergistic effect of the biphasic solvents (decalin and water) and the Ru/Nb₂O₅-MC composite catalysts, which might stabilize the emulsions and decrease the activation energy of HDO, was investigated. Meanwhile, other probe reactions were conducted to elucidate the mechanism of the HDO of phenol. The application of the efficient biphasic catalytic process may provide a promising approach for improving lignin valorization.