Harnessing the structural attributes of NiMg-CUK-1 MOF for the dual-function capture and transformation of carbon dioxide into methane

Carbon capture and conversion into chemical fuels are often considered distinct processes, whereby a sorbent is responsible for enriching a CO2 stream while a catalyst facilitates transformation into value-added commodities. Herein, we implement NiMg-CUK-1, a metal–organic framework (MOF) possessing the characteristics of both adsorbent and catalyst for the sequential capture and conversion of CO2 to methane (CH4). By harnessing the disparity in thermal stability between Ni- and Mg-CUK-1 analogues, Ni nanoparticles are preferentially generated throughout the preserved Mg portion of the framework. Tuning the Ni:Mg ratio and the NiMg-CUK-1 treatment temperature maximizes catalytic performance while preserving a substantial portion of the CO2 capture functionality inherent to the MOF. The optimized NiMg-CUK-1 is deployed in a dual-mode reactor system that alternates between ambient temperature CO2 capture and methanation under mild reaction conditions (250 °C). After five cycles, the optimal NiMg-CUK-1 reaches a levelled-out performance of 1.46 ± 0.24 mmol CO2 captured g−1, and 1.52 ± 0.23 mmol CH4 produced g−1, surpassing similar sorbent-based catalysts reliant on the chemical looping of metal oxides and carbonates. The introduced approach paves the way for combined capture and conversion of CO2 using a single dual-functional material capable of both low-temperature CO2 desorption and CH4 production.