Modulated self-assembly of three flexible Cr(<scp>iii</scp>) PCPs for SO₂ adsorption and detection

Abstract

Modulated self-assembly protocols are used to develop facile, HF-free syntheses of the archetypal flexible PCP, MIL-53(Cr), and novel isoreticular analogues MIL-53(Cr)-Br and MIL-53(Cr)-NO₂. All three PCPs show good SO₂ uptake (298 K, 1 bar) and high chemical stabilities against dry and wet SO₂. Solid-state photoluminescence spectroscopy indicates all three PCPs exhibit turn-off sensing of SO₂, in particular MIL-53(Cr)-Br, which shows a 2.7-fold decrease in emission on exposure to SO₂ at room temperature, indicating potential sensing applications.