Post-synthetic incorporation of nickel into CPO-27(Mg) to give materials with enhanced permanent porosity†
Abstract
Nickel cations have been introduced into framework sites of the magnesium dioxiterephthalate MOF, CPO-27(Mg), via a procedure involving post-synthetic treatment with an aqueous solution of Ni2+ cations and a weak acid. The final solids have Ni concentrations up to 70 mol% of the total cation content. Selected area EDX analysis, synchrotron X-ray powder diffraction and XPS surface analysis indicate that Ni2+ is distributed throughout the crystals with highest concentration at the external surface. A mechanism involving both crystallisation and predominant isomorphous cation replacement is proposed. The modified solids have much enhanced adsorption capacities following simple thermal evacuation under vacuum than unmodified CPO-27(Mg), particularly for N2 at 77 K, for which uptakes of 17 mmol gā1 are achieved. This is attributed to surface modification that makes the surface more stable to heating under evacuation.
- This article is part of the themed collection: Structural Design of Coordination Polymers