Enhanced hydrophobic MIL(Cr) metal-organic framework with high capacity and selectivity for benzene VOCs capture from high humid air

•Naphthalene dicarboxylic acid was used as ligand to synthesize a hydrophobic MOF.•MIL(Cr)-Z1 possess high surface area and high benzene uptake at low pressures.•Benzene diffusivity was 30-40 times higher than water molecules on MIL(Cr)-Z1.•Water uptake on MIL(Cr)-Z1 was 13% of that on MIL(Cr)-101 at 80 RH%.•MIL(Cr)-Z1 had a high benzene working capacity under high humid conditions.

A novel enhanced hydrophobic MIL(Cr) metal-organic framework was obtained by using naphthalene dicarboxylic acid as ligand and its adsorption equilibrium, diffusion kinetics and competitive adsorption for benzene and water were investigated systematically. Results show that: (1) the MIL(Cr)-Z1 possessed similar crystal structure and morphology to the MIL(Cr)-101. It had high surface area of 3008 m2/g with smaller window apertures (6.9 Å) and pore cages (23.3 Å) than MIL(Cr)-101; (2) it had high benzene uptake of ∼7.0 mmol/g with the isosteric heat of ∼51 kJ/mol and high benzene diffusivity (30-40 times quicker than water molecules); (3) it showed an improved hydrophobic property with very low adsorbed amount for water vapor, only about 9.84 mmol/g and 13% of that on MIL(Cr)-101 at 80 RH% and 298 K; (4) breakthrough curves show that MIL(Cr)-Z1 had high working capacity for benzene, which was 58% higher than that of MIL(Cr)-101 at 60 RH%. Thus, high adsorption capacity and selectivity for benzene VOCs make enhanced hydrophobic MIL(Cr)-Z1 a promising candidate for benzene VOCs capture under high-moisture environments.

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