Alkenone-enol-alkenone [2+2+2] Cyclotrimerization Producing Functional Coordination Polymers with Excellent Adsorption Performance.

[2+2+2] cycloaddition reactions are one of the most elegant routes for the construction of six-membered rings. Here, we report initially the alkenone-enol-alkenone [2+2+2] cycloaddition reaction and introduce the cycloaddition into the system of in situ building complexes, where three novel coordination polymers (CPs) with functional groups, namely {[CdCl2(L1)]} n (1), {[CdCl2(L2)]} n (2), and {[CdCl2(L3)]} n (3), have been obtained. Particularly, the new 1,2,3,4,5-pentasubtituted cyclohexanols ligands L1, L2, and L3 are created from the starting chalcone derivatives via the [2+2+2] cyclotrimerization. Cadmium chloride not only plays the role of constructing CPs but also acts as a catalyst to promote the cycloaddition reaction. In addition, benefiting from numerous exposed carbonyl and hydroxyl function groups, CPs 1-3 are applied to the adsorptive removal of dyes (congo red (CR) and methyl orange (MO)) from aqueous solutions. As a result, 1-3 show excellent dye adsorption capacity. 1 exhibits maximum CR adsorption capacity of 485.4 mg g-1, and 3 has ultrahigh MO uptake capacity of 492.6 mg g-1. Experimental results suggest that the dye removal effect derives from the interactions between dye molecules and the exposed carbonyl and hydroxyl groups.