A Cu(i) metal–organic framework with 4-fold helical channels for sensing anions

A new Cu(I) metal–organic framework, {[Cu(pytpy)]·NO3·CH3OH}∞ (1), which is a 4-fold interpenetrating 3D framework with (10,3)-b topology, has been synthesized by self-assembly of Cu(NO3)2·3H2O with 2,4,6-tris(4-pyridyl)pyridine (pytpy) in mixed-solvent. The guest methanol molecules in the channels of 1 could be replaced by water molecules via a single-crystal-to-single-crystal (SC–SC) process, and the hydrated complex could serve as a host for sensing anions with different geometries which can be conveniently recognized visually. Moreover, the desolvated complex shows selective uptake of CO2 over N2 at ambient temperature.