Rational Fine‐Tuning of MOF Pore Metrics: Enhanced SO2 Capture and Sensing with Optimal Multi‐Site Interactions

Abstract

Selective capture of sulfur dioxide (SO2), important in the context of environmental protection, is reachable by specially tailored porous materials endowed with physisorptive complementarity. Metal–organic frameworks (MOFs) can potentially be leading materials for physisorptive SO2 capture due to their excellent tailorability. Here, a series of highly stable DMOFs, [Ni2L2(DABCO)], where L = 1,4-benzenedicarboxylate (BDC), 1,4-naphthalenedicarboxylate (NDC), 2,6-naphthalenedicarboxylate (2,6-NDC), 9,10-anthracendicarboxylate (ADC), and 1,4-diazabicyclo[2,2,2]octane (DABCO) aiming at optimal SO2 physisorption characteristics, is reported. The extension of the aromatic core by conjugated benzene rings allows to reach an optimal pore diameter at 4–5 Å in the case of the DMOF-ADC, maximizing the multi-site MOF···SO2 interactions, which improve the SO2 binding at low concentrations, as revealed by density-functional theory (DFT) calculations. The improved SO2 separation performance of DMOF-ADC is demonstrated by single SO2 and SO2/CO2-mixed-component adsorption (a SO2/CO2 selectivity >100 is reached at 0.01 bar, which is significantly better than the value for the benchmark DUT-8 material) and dynamic breakthrough experiment. The use as a chemiresistive sensor for SO2 sensing is demonstrated for the best performing DMOF-ADC at low concentrations (doubled resistive response at 100 ppm and T < 120 °C).