We used molecular simulation to investigate NTE for a number of mesoporous MOFs. Given that MOFs have framework structures with large internal voids, perhaps unsurprisingly, they all showed contraction following a temperature increase, or NTE. The MOFs demonstrate impressive values of NTE > 50 MK -1 , but more importantly, the magnitude of contraction for the temperature range 40-400 K is extremely large, with MOF-399 exhibiting more than 3 % volume contraction.