Bottleneck Effect of N,N-Dimethylformamide in InOF-1: Increasing CO Capture in Porous Coordination Polymers.

The bottleneck effect of confined N,N-dimethylformamide (DMF) molecules was observed in InOF-1 for the first time: CO capture was remarkably enhanced in samples of as-synthesized InOF-1, thermally activated in such a way that a small residual amount of DMF molecules remained confined within the pores (DMF@InOF-1). Dynamic CO adsorption experiments on DMF@InOF-1 exhibited a CO capture of 8.06 wt % [1.5-fold higher than that of a fully activated InOF-1 (5.24%)]. DMF@InOF-1 can reversibly adsorb/desorb 8.09% CO with no loss of CO capacity after 10 cycles, and the desorption is accomplished by only turning the CO flow off. Static CO adsorption experiments (at 196 K) demonstrated a 1.4-fold CO capture increase (from 5.5 mmol·g, fully activated InOF-1, to 7.5 mmol·g, DMF@InOF-1). Therefore, these CO capture properties are the result of the presence of residual-confined DMF molecules within the InOF-1 framework and their interactions via a very strong hydrogen bond with the In(μ-OH) groups, which prevent DMF leaching. The stability of this hydrogen bond is given by a perfect fit of the DMF molecule in the "dent" around the OH group that allows a nearly ideal orientation of the DMF molecule towards the OH group.