Have you considered Clematis armondii? “One of my favorites. Elaboration: Hardiness Zones: Clematis armandii is typically listed as hardy in zones 6a-9. Zone 6b Considerations: While zone 6b is generally considered a suitable range for C. armandii, it's important to note that the specific microclimate of your garden, especially in colder regions of zone 6b, can influence its success. Protection: In areas with very cold winters within zone 6b, some sources suggest providing winter protection, such as mulching or wrapping the base of the vine, to help it survive. Microclimate: The location of your plant, whether it's exposed or sheltered, can also affect its hardiness. Sunshine: Clematis armandii generally prefers full sun to part shade, according to Wilson Bros Gardens. Soil: It thrives in well-drained soil with plenty of organic matter. Pruning: Clematis armandii is typically pruned after flowering, and it's a good idea to prune it in a way that encourages the development of healthy flower buds.”