Size-exclusive and coordination-induced selective dye adsorption in a nanotubular metal-organic frameworkElectronic supplementary information (ESI) available: The details of structure refinement of BUT-51, selected bond distances and angles, TGA, dye molecular structures, and additional dye adsorption/release. CCDC 1037586. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5ta00963d

A new metal-organic framework, {[(CH 3 ) 2 NH 2 ][Co 2 NaL 2 (CH 3 COO) 2 ]· x S} n (BUT-51, H 2 L = 5-(pyridine-4-yl)isophthalic acid) with two types of nanotubular channels, was synthesized and used in dye adsorption. It was found that cationic dyes, including Methylene Blue (MB), Acridine Red (AR) and Acriflavine Hydrochloride (AH), can be rapidly adsorbed by BUT-51, but larger Methylene Violet (MV) and anionic Methyl Orange (MO), as well as neutral Solvent Yellow 2 (SY2), can hardly be adsorbed. These results imply that the adsorption behaviour of BUT-51 with the cationic dyes follows not only a charge- but also size- and shape-exclusive effect. Surprisingly, BUT-51 also preferentially adsorbs (or separates) AH from MB and AR, respectively, in their mixed acetone solution, probably due to the coordination between AH and Co 2+ in its framework. Furthermore, AH uptake can change the porosity and framework stability of BUT-51 to give a robust partner. A nanotubular MOF, BUT-51, performs coordination-induced selective dye adsorption, which changes its stability and porosity to give a robust partner.