Although zeolites and related materials combine nanoporosity with high thermal stability, they are difficult to modify or derivatize in a systematic way. A highly porous metal coordination polymer [Cu-3(TMA)(2)(H2O)(3)](n) (where TMA is benzene-1,3,5-tricarboxylate) was formed in 80 percent yield. It has interconnected [Cu-2(O2CR)(4)] units (where R is an aromatic ring), which create a three-dimensional system of channels with a pore size of 1 nanometer and an accessible porosity of about 40 percent in the solid. Unlike zeolites, the channel Linings can be chemically functionalized; for example, the aqua ligands can be replaced by pyridines. Thermal gravimetric analysis and high-temperature single-crystal diffractometry indicate that the framework is stable up to 240 degrees C.