Self-adjusting binding pockets enhance H2and CH4adsorption in a uranium-based metal-organic framework

A new, air-stable, permanently porous uranium(iv) metal-organic framework U(bdc)(2)(1, bdc(2-)= 1,4-benzenedicarboxylate) was synthesized and its H(2)and CH(4)adsorption properties were investigated. Low temperature adsorption isotherms confirm strong adsorption of both gases in the framework at low pressures.In situgas-dosed neutron diffraction experiments with different D(2)loadings revealed a rare example of cooperative framework contraction (Delta V= -7.8%), triggered by D(2)adsorption at low pressures. This deformation creates two optimized binding pockets for hydrogen (Q(st)= -8.6 kJ mol(-1)) per pore, in agreement with H(2)adsorption data. Analogous experiments with CD4(Q(st)= -24.8 kJ mol(-1)) andN,N-dimethylformamide as guests revealed that the binding pockets in1adjust by selective framework contractions that are unique for each adsorbent, augmenting individual host-guest interactions. Our results suggest that the strategic combination of binding pockets and structural flexibility in metal-organic frameworks holds great potential for the development of new adsorbents with an enhanced substrate affinity.