Emissive fluoren-triangles for solid-state fluorochromism and selective gas sorption

In this work, we first present a new class of fluorescent synthetic macrocycle, named fluoren-triangle (FT), which we designed by creatively integrating the fluorene fluorophore into the resorcinarene backbone. Single-crystal analysis of FT revealed isosceles-triangle conformations accompanied by a layer-like molecular assembly in the solid state. Fluorescence experiments demonstrated its aggregation-induced emission character and tunable solid-state fluorescence emission, and per-methylated FT (MeFT) also exhibited an intriguing excitation-wavelength-dependent (Ex-De) capability with different emission color-switching processes. Significantly, the activated powders of per-hydroxylated FT (OHFT) and MeFT with both nonporous and amorphous features displayed remarkable potential in constructing adsorptive separation materials for CO2 and CH4 capture, affording good selectivities of 31/1 for CO2/N2 (by OHFT) and 8/1 for CH4/CO2 (by MeFT), respectively. The discovery of FT will provide new perspectives in constructing novel fluorescent macrocycles and functional photo-responsive materials, unleashing new inspirations in molecular sorbents for gas adsorption and separation.