Construction of Highly Mesoporous Metal-Organic Frameworks via Green Metallic Solvents Assisted Route for Chemical CO Fixation.

An easy and versatile method of constructing hierarchically micro- and mesoporous metal-organic frameworks (MOFs) using newly synthesized green metallic solvents (GMS) is proposed. This method can generally be applied to several different series of MOFs. For the first time synthesized, GMS are eco-friendly, easily synthesizable, and play multiple roles of pore expanders, structure directing agents, and bring an additional ligand into the MOF structure. Hierarchically assembled MOF materials via MGS-assisted route showed highly improved structural properties and are exceptionally adjustable regarding all important structural parameters. Compared to its pristine MOF, hierarchically constructed relineMg@UiO-66 showed almost 2.5 times higher surface area, 3 times increased total pore volume, and large mesopores (17-31 nm). In addition to 84.65 mg g CO adsorption capacity of relineMg@UiO-66, which is almost 243% increase over its pristine UiO-66 (34.89 mg g), relineMg@UiO-66 displays long-term cyclic performance with 94.8% capacity retention over ten consecutive cycles. Moreover, relineMg@UiO-66 exhibits outstanding heterogeneous catalytic activity (yield≈97%) in a CO cycloaddition reaction with different epoxides. Density functional theory (DFT) calculations reveal that the judicious tuning of Zr-O coordination environment with GMS optimized secondary building unit (SBU) of Zr(µ-O)(µ-OH)-(CO) cluster with OH-symmetry in MOF's frameworks assembly for enhanced adsorption and heterogeneous catalysis.