UC Berkeley

We present the in silico design of a MOF-74 analogue, hereon known as M₂(DHFUMA) [M = Mg, Fe, Co, Ni, Zn], with enhanced small-molecule adsorption properties over the original M₂(DOBDC) series. Constructed from 2,3-dihydroxyfumarate (DHFUMA), an aliphatic ligand which is smaller than the aromatic 2,5-dioxidobenzene-1,4-dicarboxylate (DOBDC), the M₂(DHFUMA) framework has a reduced channel diameter, resulting in higher volumetric density of open metal sites and significantly improved volumetric hydrogen (H₂) storage potential. Furthermore, the reduced distance between two adjacent open metal sites in the pore channel leads to a CO₂ binding mode of one molecule per two adjacent metals with markedly stronger binding energetics. Through dispersion-corrected density functional theory (DFT) calculations of guest-framework interactions and classical simulation of the adsorption behavior of binary CO₂:H₂O mixtures, we theoretically predict the M₂(DHFUMA) series as an improved alternative for carbon capture over the M₂(DOBDC) series when adsorbing from wet flue gas streams. The improved CO₂ uptake and humidity tolerance in our simulations is tunable based upon metal selection and adsorption temperature which, combined with the significantly reduced ligand expense, elevates this material's potential for CO₂ capture and H₂ storage. The dynamical and elastic stabilities of Mg₂(DHFUMA) were verified by hybrid DFT calculations, demonstrating its significant potential for experimental synthesis.