This paper presents a defect-tolerant architecture for molecular-based memories. A memory is designed from multiple modules that share the same address space, where each of the modules is constructed as a molecular-based crossbar array. Redundant rows and columns of each crossbar array and redundant modules with a proper assignment of control variables are utilized to tolerate defects generated during the fabrication process and faults occurring during normal operation. The crossbar area required for the molecular memory can be made smaller than those of existing schemes, while achieving higher memory configurability. An extensive simulation demonstrates that the proposed memory architecture outperforms existing molecular-based redundant memory architectures for a wide range of defect rates.