One-step microwave-assisted synthesis of amino-functionalized chromium(III) terephthalate MIL-101-NH2

Abstract

A single-step microwave (MW)-assisted protocol for the synthesis of MIL-101(Cr) and of MIL-101(Cr)-NH2 is described herein, based on the addition of NaF as the modulator instead of hydrofluoric acid to obtain the corresponding polymers in only 1 h with high crystallinity and yields (>70%, 0.5 g). Compared to classic solvothermal protocols (12–72 h, <30%), MW-assisted synthesis allowed shorter reaction time and improved yields, replacing N,N-dimethylformamide by water. Physicochemical properties of MIL-101(Cr)-NH2 and MIL-101(Cr) obtained through this MW-assisted procedure are more homogenous than those observed for the corresponding solvothermal counterparts, and interestingly, enhanced higher control over nanometric particle size (80–130 vs 400–1000 nm), lower polydispersity, and higher Brunauer-Emett-Teller surface area (2000–2700 vs 1800–2300 m2/g) were observed because of the better accessibility and diffusion of gases throughout the internal pores.