A copper trimesate selenite compound is reported which shows a robust 3-D porous structure with unprecedented structural characteristics and represents a unique example of a metal inorganic–organic framework with considerable permanent microporosity and selective CO 2 sorption properties. The synthesis and study of Metal Organic Frameworks (MOFs) or Porous Coordination Polymers (PCPs) have risen to the forefront of inorganic and materials science research. 1,2 This is not surprising taking into account the exceptional properties of these compounds and potential applications in various fields including gas storage and separation, catalysis, sensing, drug delivery, etc. 1,2 Besides tuning the properties of existing MOFs, it is also of great importance to discover new compounds that may exhibit features not observed for the already reported materials. A strategy that can afford MOFs with unprecedented structures and properties involves the simultaneous use of polytopic organic ligands and inorganic anions with metal binding capability, such as SO 4 2− , PO 4 3− , SO 3 2− , SeO 3 2− , TeO 3 2− , CO 3 2− , etc. 3 Such MOFs, which can be called Metal Inorganic Organic Frameworks (MINOFs), may show not only unique structural characteristics but also properties arising from the presence of inorganic anionic ligands, making them a distinct class of metal organic framework materials. For example, it is well known that the incorporation of QO 3 2− (Q = S, Se, Te) anions often leads to non-centrosymmetric structures due to the lone pair of electrons of these ligands and many acentric compounds with these anions display interesting non-linear optical properties (e.g. Second Harmonic Generation, SHG). 4 So far, MOFs containing bridging inorganic anionic groups in combination with organic polytopic ligands have been reported sporadically 3 and in addition, the vast majority of such materials described in the literature are nonporous with very few exceptions. 3k Herein we present the compound [Cu 4 (btc) 2 (SeO 3)(H 2 O) 2 ]·6H 2 O (MINOF-1) (H 3 btc = 1,3,5-benzenetricarboxylic acid), which exhibits a robust 3-D open framework structure and also adopts a highly unusual structural topology as a result of the insertion of SeO 3 2− ligands into the copper trimesate net. Importantly, MINOF-1 represents a unique example of a coordination polymer based on both organic and inorganic polytopic ligands that shows significant permanent micropo-rosity and high CO 2 uptake and selectivity vs. CH 4 . Compound MINOF-1 was isolated as plate-like crystals (Fig. S1, ESI) by the reaction of Cu(NO 3) 2 ·3H 2 O, H 3 btc and KSeCN in EtOH : H 2 O (1 : 1) at 90 °C. The SeO 3 2− ligands are presumably formed in situ by the decomposition of SeCN