How to combine images into a PDF ordered by the time that they were taken?

Question

I am attempting to compile a folder of images into a single PDF by the order in which they were taken.

os.getcwd()
os.chdir(folder_path)

a= glob.glob(folder_path)
b = [os.path.getctime(i) for i in a]
c = {}
for i,j  in list(zip(a,b)):
    c[i] = j
sorted_c = dict(sorted(c.items(), key=operator.itemgetter(1),reverse=False))
with open("output.pdf", "wb") as f:
    f.write(img2pdf.convert([k for k in sorted_c]))

For some reason

 with open("output.pdf", "wb") as f:
    f.write(img2pdf.convert([k for k in sorted_c]))

keeps throwing TypeError: a bytes-like object is required, not 'str' Alternate methods to accomplish this are also welcome.