why i cannot await 'System.Linq.IQueryable

I have the following repository method:-

  public  IQueryable<TSet> getAllScanEmailTo()
        {
         return   t.TSets.Where(a=>a.Name.StartsWith("ScanEmail"));

        }

which is being called as follow:-

var emailsTo = repository.getAllScanEmailTo().ToList();

now i tried to change the above to be using async so i modifed my repository method to be as follow:-

 public async Task<  IQueryable<TSet>> getAllScanEmailTo()
        {
         return  await t.TSets.Where(a=>a.Name.StartsWith("ScanEmail"));

        }

but i got the following error :-

Error   1   Cannot await 'System.Linq.IQueryable<Final.Models.TSet>'