Idiosyncrasies of Co2(dhtp): In situ-annealing by methanol

Structural instability in humid surroundings is one of the major drawbacks of many metal organic frameworks (MOF5) compared to zeolites. In this study we investigate the pronounced sensitivity of MOF Co-2(-dhtp) (Co-MOF-74 or CPO-27-Co) towards humid air. Guest uptake in big Co-2(dhtp) crystals has been studied by IR microscopy. We found that already a short exposure of 30 s to moist air causes a surface blockage, completely preventing the adsorption of even small guest molecules. It could be confirmed in complementary PXRD measurements that the interior of the crystals remains intact during such short exposure times. Indications for a loss of crystallinity were evidenced only for notably longer exposure times (4 h). Most remarkably, the defects could at least be partially annealed in methanol atmosphere. Reversible adsorption of hydrocarbons in initially blocked crystals was found after exposing the crystals to methanol vapor for about 0.5 h. (C) 2013 Elsevier Inc. All rights reserved.