The use of metal–organic frameworks for CO purification

Abstract

Metal organic frameworks (MOFs) as adsorbents present a potentially cost effective and energy saving alternative to current technologies used to purify carbon monoxide (CO), a reagent in numerous industrial processes. This review compares the different mechanisms involved in CO adsorption in MOFs, highlighting the desired chemical and structural features for this process. An outlook on future directions for research on MOFs for CO adsorption is proposed.

Highly Porous Carbon Xerogels Doped with Cuprous Chloride for Effective CO Adsorption

“…Here, Cu–C bonds are formed after the interaction of the CuCl-doped CXs and CO molecules. 32 The introduction of Cu + into CX can improve the CO adsorption capacity considerably and hardly affect the desorption capacity of samples. The high CO adsorption capacity of CuCl-doped CXs benefits from the combination of physical and chemical adsorption, whereas CXs and AC can only depend on physical adsorption.…”

Optimisation of Cu+ impregnation of MOF-74 to improve CO/N2 and CO/CO2 separations

“…2 MOFs have shown the most promising performance to date, 6 recording the highest CO adsorption uptakes and theoretical CO/X selectivities (where X ¼ H 2 , N 2 and CH 4 ). 5,7 MOFs are formed by organic linkers coordinating to metal nodes (or polynuclear clusters). 8 Their metal sites can provide coordinatively unsaturated metal sites, also known as openmetal sites, which have an affinity for CO. 5 Hence, the best performing MOFs are highly dependent on the MOFs' metal sites as they determine the metal-CO bond strength through both s-bond formation and p-backdonation.…”

“…5,7 MOFs are formed by organic linkers coordinating to metal nodes (or polynuclear clusters). 8 Their metal sites can provide coordinatively unsaturated metal sites, also known as openmetal sites, which have an affinity for CO. 5 Hence, the best performing MOFs are highly dependent on the MOFs' metal sites as they determine the metal-CO bond strength through both s-bond formation and p-backdonation. 9 A comprehensive study by Bloch et al reported high CO capacities and CO/H 2 and CO/N 2 selectivities for MOF-74 (also known as CPO-27 or M 2 (DOBDC), DOBDC ¼ 2,5-dioxido-1,4-benzenedicarboxylate).…”

“…While Cu impregnated materials typically perform better for CO separation than the unimpregnated materials, their CO capacity and theoretical selectivities still fall short of the best performing MOFs. 5,7 Impregnation has also been performed on MOFs to improve their CO separation performance. Cu + metal sites have been incorporated on Fe-MIL-100 for CO/N 2 via impregnation with Cu 2+ -based salts followed by reduction to Cu + .…”

“…To achieve this, we have performed a systematic Cu impregnation study on Ni-MOF-74 and Co-MOF-74. 5,7 We have: (i) synthesized Cu + -impregnated MOF-74 structures to simultaneously use the metal-CO binding strength of the framework M 2+ and introduce additional Cu + ions, (ii) optimised the Cu impregnation and monitored in situ the Cu 2+ to Cu + reduction process using X-ray absorption near edge structure (XANES) analysis, (iii) veried Cu + -CO and M 2+ -CO binding using in situ DRIFTS analysis and (iv) tested Cu@Ni-MOF-74 for dynamic CO/N 2 and CO/CO 2 separation.…”