Confinement Effects in Well-Defined Metal–Organic Frameworks (MOFs) for Selective CO2 Hydrogenation: A Review

Abstract

Decarbonization has become an urgent affair to restrain global warming. CO2 hydrogenation coupled with H2 derived from water electrolysis is considered a promising route to mitigate the negative impact of carbon emission and also promote the application of hydrogen. It is of great significance to develop catalysts with excellent performance and large-scale implementation. In the past decades, metal–organic frameworks (MOFs) have been widely involved in the rational design of catalysts for CO2 hydrogenation due to their high surface areas, tunable porosities, well-ordered pore structures, and diversities in metals and functional groups. Confinement effects in MOFs or MOF-derived materials have been reported to promote the stability of CO2 hydrogenation catalysts, such as molecular complexes of immobilization effect, active sites in size effect, stabilization in the encapsulation effect, and electron transfer and interfacial catalysis in the synergistic effect. This review attempts to summarize the progress of MOF-based CO2 hydrogenation catalysts up to now, and demonstrate the synthetic strategies, unique features, and enhancement mechanisms compared with traditionally supported catalysts. Great emphasis will be placed on various confinement effects in CO2 hydrogenation. The challenges and opportunities in precise design, synthesis, and applications of MOF-confined catalysis for CO2 hydrogenation are also summarized.

Zr-Based MOF-545 Metal–Organic Framework Loaded with Highly Dispersed Small Size Ni Nanoparticles for CO2 Methanation

“…In the past decade, there has been a surge of interest in MOFs within the realms of CO 2 adsorption, gas separation, and catalysis owing to their remarkable attributes such as a large surface area, tunable porosity, strong metal binding sites, and the capacity for tailored metal–support interactions . In the field of CO 2 hydrogenation, MOFs have emerged as pivotal supports or sacrificial precursors, playing a promising role in the fabrication of efficient catalysts. − MOF-based catalysts may be specifically designed to ensure the uniform dispersion of metal nanoparticles (NPs) and augment the interplay between NPs and the support, effectively preventing the undesired phenomena of sintering and aggregation of active metal species. , In particular, a number of Ni-containing MOF catalysts have been reported in the past decade for CO 2 methanation, exploiting the high dispersion of small-size Ni NPs, including Ni@MOF-5, Ni@MIL-101-Cr, , and Ni@UiO-66. , Moreover, MOF-derived Ni-containing systems have been also reported as sacrificial precursors for the synthesis of efficient catalytic materials, via high temperature (>500 °C) pyrolysis. − Overall, these studies shed light on key features that determine the performances of these Ni-based catalysts, such as the impact of the metal immobilization methods, the nickel reduction conditions, or the Ni loading, in addition to the catalytic conditions themselves (temperature, reactants ratio,...). In parallel, the catalytic activities are also known to be strongly dependent on the support used (SiO 2 , CeO 2 , TiO 2 , ZrO 2, or MgO) .…”

Current Trends in MOF (Metal-Organic Framework) and Metal X-ides

“…Lin et al [ 12 ] recently summarized the progress of MOF-based CO 2 hydrogenation catalysts and compared their synthetic strategies, unique features, and enhancement mechanisms with traditionally supported catalysts. The challenges and opportunities pertaining to the precise design, synthesis, and applications of MOF-based CO 2 hydrogenation catalysts were also summarized.…”