Molecular level characterization of hydrogen binding in porous materials is essential for the ultimate utilization of hydrogen in energy related applications. The most powerful experimental probe of the interactions of hydrogen with porous materials is the inelastic neutron scattering (INS) spectroscopy of the hindered rotations of the adsorbed hydrogen molecule. Analysis of such spectra by a combination of an accurate potential energy surface (PES) with exact calculations of the 2D rotational quantum dynamics provides a stringent test of such interactions. Various calculations have given accurate H2 binding energies, but may be inadequate when the resulting PES is used to obtain the rotational transitions for H2. We describe a series of such computational studies on large clusters of MOF-74 and MOF-5 using MP2 methods as well as DFT with recent dispersion corrected functionals, and assess the accuracy of the resulting PES by comparison of rotational transitions with experimental INS spectra.