Mesoporous single-atom and nano-confined catalysts: Enabling low-energy integrated CO2 capture and direct conversion

Mesoporous architecture confinement engineering has become an effective approach to address major limitations of single-atom catalysts (SACs) and integrated CO 2 capture-conversion systems. These techniques may provide enhanced control of the spatial distribution, local microenvironment and pore size to attain high activity, selectivity and permanence in photocatalytic and electrocatalytic CO 2 reduction. The recent trends in confinement mechanisms that have been highlighted in the present paper include two step space-confinement pyrolysis, hierarchical porosity in MOFs, single-micelle assembly and defect engineering. These methods enable the fabrication of well-defined nanoreactors, allowing synergistic reactions between photoactive and catalytic species, cascade reactions, tremendous charge separation and carrier lifetimes. Mesoporous supports with both single-atom and dual-atom sites are given special consideration, where tunable coordination environments and dynamic structural evolution under operating conditions play critical roles in dictating selectivity to high value C 1 or C 2 products at low over potentials. When mesoporous SAC systems are compared with traditional amine-based sorbents and nanoparticle catalysts, it can be seen that mesoporous materials have clear advantages in regard to regeneration energy, humidity resistance, cycling stability, and combined capture-conversion efficiency. Physical confinement and electronic modulation (with a state-of-the-art inverse design and Bayesian optimization) offers the paradigm of scalable, energy-efficient use of CO 2 . Finally, low active-site density, long-term stability, and industrial translation have been identified as key issues and a roadmap to the future that incorporates the development of hierarchical multi-scale porous structures to host both SACs, full CCUS loops with renewables, and technologies that produce negative emissions using the sun as the power source have been discussed.