Highly stable two-dimensional metal–organic frameworks, 2∞[FeII(L)2] (HL = 3-(2-pyridyl)-5-(3-pyridyl)-1,2,4-triazole (1) and 3-(3-methyl-2-pyridyl)-5-(3-pyridyl)-1,2,4-triazole (2), display well defined two-step spin crossover properties at remarkably high temperatures, namely, Tc1 = 329 K, Tc2 = 501 K for 1 and Tc1 = 351 K, Tc2 = 520 K for 2, which are the highest critical temperatures reported so far.
