Nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) are versatile methods in modern chemistry and biology fields. Nevertheless, they suffer from intrinsically limited sensitivity due to the low nuclear spin polarization at ambient temperature. One of the promising methods to overcome this limitation is dynamic nuclear polarization (DNP). In particular, DNP based on photoexcited triplet electrons (triplet-DNP) has the potential to hyperpolarize nuclear spins of target substrates in the low magnetic field at room temperature. Room-temperature triplet-DNP has provided high enhancements in organic crystals such as p-terphenyl. However, it remains difficult for such organic crystals to accommodate target molecules to be monitored. While amorphous solids such as o-terphenyl were employed as host matrices to accommodate target substrates, the flexible structure requires the cooling of the sample for triplet-DNP (∼120 K). Therefore, despite these efforts, it remains a grand challenge to develop a room-temperature triplet-DNP system with accessibility for polarizing targets. In this work, we report the first example of triplet-DNP of nanoporous metal-organic frameworks (J. Am. Chem. Soc. 2018, 140, 15606-15610). We modified the typical polarizing agent pentacene with metal-coordinating carboxylate moieties (4,4′-(pentacene-6,13-diyl)dibenzoic acid (PDBA)) for its introduction into MOFs. A relatively long 1H T1 has been reported for a prototypical diamagnetic Zn2+-based MOF, [Zn(MeIM)2]n (ZIF-8; MeIM = 2-methylimidazolate). A partial deuteration of MeIM ligands allows the elongation of T1 of partially deuterated D-ZIF-8. Polarization transfer from PDBA triplet electrons to 1H nuclei in D-ZIF-8 resulted in a clear enhancement (ε = 58) of 1H NMR signals of D-ZIF-8 at a low magnetic field of 0.67 T and room temperature.