How about:
df <- data.frame(matrix(ncol = 3, nrow = 0))
x <- c("name", "age", "gender")
colnames(df) <- x
To do all these operations in one-liner:
setNames(data.frame(matrix(ncol = 3, nrow = 0)), c("name", "age", "gender"))
#[1] name age gender
#<0 rows> (or 0-length row.names)
Or
data.frame(matrix(ncol=3,nrow=0, dimnames=list(NULL, c("name", "age", "gender"))))