MCl2 complexes of a new p-carboxylated 1,2-bis(diphenylphosphino)benzene ligand are effectively utilized as tetratopic building blocks to prepare isostructural porous coordination polymers with accessible reactive metal sites (M = Pd, Pt). The crystalline materials exhibit unusual and fully reversible H-2 sorption at 150 degrees C. Post-synthetic reactivity is also possible, in which Pt-Cl bonds can be activated to provide organometallic species in the pores.